SUBCHAPTER C—AIR PROGRAMS - US EPA · averages using 18, 19, etc. as the divi-sor. If fewer than 18 hourly averages are available, but the 24-hour average would exceed the level

5

SUBCHAPTER C—AIR PROGRAMS

PART 50—NATIONAL PRIMARY ANDSECONDARY AMBIENT AIRQUALITY STANDARDS

Sec.50.1 Definitions.50.2 Scope.50.3 Reference conditions.50.4 National primary ambient air quality

standards for sulfur oxides (sulfur diox-ide).

50.5 National secondary ambient air qualitystandard for sulfur oxides (sulfur diox-ide).

50.6 National primary and secondary ambi-ent air quality standards for PM10.

50.7 National primary and secondary ambi-ent air quality standards for particulatematter.

50.8 National primary ambient air qualitystandards for carbon monoxide.

50.9 National 1-hour primary and secondaryambient air quality standards for ozone.

50.10 National 8-hour primary and sec-ondary ambient air quality standards forozone.

50.11 National primary and secondary ambi-ent air quality standards for nitrogen di-oxide.

50.12 National primary and secondary ambi-ent air quality standards for lead.

APPENDIX A TO PART 50—REFERENCE METHODFOR THE DETERMINATION OF SULFUR DIOX-IDE IN THE ATMOSPHERE (PARAROSANILINEMETHOD)

APPENDIX B TO PART 50—REFERENCE METHODFOR THE DETERMINATION OF SUSPENDEDPARTICULATE MATTER IN THE ATMOS-PHERE (HIGH-VOLUME METHOD)

APPENDIX C TO PART 50—MEASUREMENT PRIN-CIPLE AND CALIBRATION PROCEDURE FORTHE MEASUREMENT OF CARBON MONOXIDEIN THE ATMOSPHERE (NON–DISPERSIVE IN-FRARED PHOTOMETRY)

APPENDIX D TO PART 50—MEASUREMENT PRIN-CIPLE AND CALIBRATION PROCEDURE FORTHE MEASUREMENT OF OZONE IN THE AT-MOSPHERE

APPENDIX E TO PART 50 [RESERVED]APPENDIX F TO PART 50—MEASUREMENT PRIN-

CIPLE AND CALIBRATION PROCEDURE FORTHE MEASUREMENT OF NITROGEN DIOXIDEIN THE ATMOSPHERE (GAS PHASECHEMILUMINESCENCE)

APPENDIX G TO PART 50—REFERENCE METHODFOR THE DETERMINATION OF LEAD IN SUS-PENDED PARTICULATE MATTER COLLECTEDFROM AMBIENT AIR

APPENDIX H TO PART 50—INTERPRETATION OFTHE 1-HOUR PRIMARY AND SECONDARY NA-TIONAL AMBIENT AIR QUALITY STANDARDSFOR OZONE

APPENDIX I TO PART 50—INTERPRETATION OFTHE 8-HOUR PRIMARY AND SECONDARY NA-TIONAL AMBIENT AIR QUALITY STANDARDSFOR OZONE

APPENDIX J TO PART 50—REFERENCE METHODFOR THE DETERMINATION OF PARTICULATEMATTER AS PM10 IN THE ATMOSPHERE

APPENDIX K TO PART 50—INTERPRETATION OFTHE NATIONAL AMBIENT AIR QUALITYSTANDARDS FOR PARTICULATE MATTER

APPENDIX L TO PART 50—REFERENCE METHODFOR THE DETERMINATION OF FINE PARTIC-ULATE MATTER AS PM2.5 IN THE ATMOS-PHERE

APPENDIX M TO PART 50—REFERENCE METHODFOR THE DETERMINATION OF PARTICULATEMATTER AS PM10 IN THE ATMOSPHERE

APPENDIX N TO PART 50—INTERPRETATION OFTHE NATIONAL AMBIENT AIR QUALITYSTANDARDS FOR PARTICULATE MATTER

AUTHORITY: 42 U.S.C. 7401, et seq.

SOURCE: 36 FR 22384, Nov. 25, 1971, unlessotherwise noted.

§ 50.1 Definitions.(a) As used in this part, all terms not

defined herein shall have the meaninggiven them by the Act.

(b) Act means the Clean Air Act, asamended (42 U.S.C. 1857–18571, asamended by Pub. L. 91–604).

(c) Agency means the EnvironmentalProtection Agency.

(d) Administrator means the Adminis-trator of the Environmental ProtectionAgency.

(e) Ambient air means that portion ofthe atmosphere, external to buildings,to which the general public has access.

(f) Reference method means a methodof sampling and analyzing the ambientair for an air pollutant that is specifiedas a reference method in an appendixto this part, or a method that has beendesignated as a reference method in ac-cordance with part 53 of this chapter; itdoes not include a method for which areference method designation has beencancelled in accordance with § 53.11 or§ 53.16 of this chapter.

(g) Equivalent method means a methodof sampling and analyzing the ambientair for an air pollutant that has beendesignated as an equivalent method inaccordance with part 53 of this chapter;it does not include a method for whichan equivalent method designation has

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40 CFR Ch. I (7–1–01 Edition)§ 50.2

been cancelled in accordance with§ 53.11 or § 53.16 of this chapter.

(h) Traceable means that a localstandard has been compared and cer-tified either directly or via not morethan one intermediate standard, to aprimary standard such as a NationalBureau of Standards Standard Ref-erence Material (NBS SRM), or aUSEPA/NBS-approved Certified Ref-erence Material (CRM).

(i) Indian country is as defined in 18U.S.C. 1151.

[36 FR 22384, Nov. 25, 1971, as amended at 41FR 11253, Mar. 17, 1976; 48 FR 2529, Jan. 20,1983; 63 FR 7274, Feb. 12, 1998]

§ 50.2 Scope.

(a) National primary and secondaryambient air quality standards undersection 109 of the Act are set forth inthis part.

(b) National primary ambient airquality standards define levels of airquality which the Administratorjudges are necessary, with an adequatemargin of safety, to protect the publichealth. National secondary ambient airquality standards define levels of airquality which the Administratorjudges necessary to protect the publicwelfare from any known or anticipatedadverse effects of a pollutant. Suchstandards are subject to revision, andadditional primary and secondarystandards may be promulgated as theAdministrator deems necessary to pro-tect the public health and welfare.

(c) The promulgation of national pri-mary and secondary ambient air qual-ity standards shall not be considered inany manner to allow significant dete-rioration of existing air quality in anyportion of any State or Indian country.

(d) The proposal, promulgation, or re-vision of national primary and sec-ondary ambient air quality standardsshall not prohibit any State or Indiancountry from establishing ambient airquality standards for that State orarea under a tribal CAA program orany portion thereof which are morestringent than the national standards.

[36 FR 22384, Nov. 25, 1971, as amended at 63FR 7274, Feb. 12, 1998]

§ 50.3 Reference conditions.All measurements of air quality that

are expressed as mass per unit volume(e.g., micrograms per cubic meter)other than for the particulate matter(PM10 and PM2.5) standards containedin § 50.7 shall be corrected to a ref-erence temperature of 25 °C and a ref-erence pressure of 760 millimeters ofmercury (1,013.2 millibars). Measure-ments of PM10 and PM2.5 for purposes ofcomparison to the standards containedin § 50.7 shall be reported based on ac-tual ambient air volume measured atthe actual ambient temperature andpressure at the monitoring site duringthe measurement period.

[62 FR 38711, July 18, 1997]

§ 50.4 National primary ambient airquality standards for sulfur oxides(sulfur dioxide).

(a) The level of the annual standardis 0.030 parts per million (ppm), not tobe exceeded in a calendar year. The an-nual arithmetic mean shall be roundedto three decimal places (fractionalparts equal to or greater than 0.0005ppm shall be rounded up).

(b) The level of the 24-hour standardis 0.14 parts per million (ppm), not tobe exceeded more than once per cal-endar year. The 24-hour averages shallbe determined from successive non-overlapping 24-hour blocks starting atmidnight each calendar day and shallbe rounded to two decimal places (frac-tional parts equal to or greater than0.005 ppm shall be rounded up).

(c) Sulfur oxides shall be measured inthe ambient air as sulfur dioxide by thereference method described in appendixA to this part or by an equivalentmethod designated in accordance withpart 53 of this chapter.

(d) To demonstrate attainment, theannual arithmetic mean and the sec-ond-highest 24-hour averages must bebased upon hourly data that are atleast 75 percent complete in each cal-endar quarter. A 24-hour block averageshall be considered valid if at least 75percent of the hourly averages for the24-hour period are available. In theevent that only 18, 19, 20, 21, 22, or 23hourly averages are available, the 24-hour block average shall be computedas the sum of the available hourly


7

Environmental Protection Agency § 50.7

averages using 18, 19, etc. as the divi-sor. If fewer than 18 hourly averagesare available, but the 24-hour averagewould exceed the level of the standardwhen zeros are substituted for themissing values, subject to the roundingrule of paragraph (b) of this section,then this shall be considered a valid 24-hour average. In this case, the 24-hourblock average shall be computed as thesum of the available hourly averagesdivided by 24.

[61 FR 25579, May 22, 1996]

§ 50.5 National secondary ambient airquality standard for sulfur oxides(sulfur dioxide).

(a) The level of the 3-hour standard is0.5 parts per million (ppm), not to beexceeded more than once per calendaryear. The 3-hour averages shall be de-termined from successive nonoverlap-ping 3-hour blocks starting at midnighteach calendar day and shall be roundedto 1 decimal place (fractional partsequal to or greater than 0.05 ppm shallbe rounded up).

(b) Sulfur oxides shall be measured inthe ambient air as sulfur dioxide by thereference method described in appendixA of this part or by an equivalentmethod designated in accordance withpart 53 of this chapter.

(c) To demonstrate attainment, thesecond-highest 3-hour average must bebased upon hourly data that are atleast 75 percent complete in each cal-endar quarter. A 3-hour block averageshall be considered valid only if allthree hourly averages for the 3-hourperiod are available. If only one or twohourly averages are available, but the3-hour average would exceed the levelof the standard when zeros are sub-stituted for the missing values, subjectto the rounding rule of paragraph (a) ofthis section, then this shall be consid-ered a valid 3-hour average. In allcases, the 3-hour block average shall becomputed as the sum of the hourlyaverages divided by 3.

[61 FR 25580, May 22, 1996]

§ 50.6 National primary and secondaryambient air quality standards forPM10.

(a) The level of the national primaryand secondary 24-hour ambient airquality standards for particulate mat-

ter is 150 micrograms per cubic meter(µg/m3), 24-hour average concentration.The standards are attained when theexpected number of days per calendaryear with a 24-hour average concentra-tion above 150 µg/m3, as determined inaccordance with appendix K to thispart, is equal to or less than one.

(b) The level of the national primaryand secondary annual standards forparticulate matter is 50 microgramsper cubic meter (µg/m3), annual arith-metic mean. The standards are at-tained when the expected annual arith-metic mean concentration, as deter-mined in accordance with appendix Kto this part, is less than or equal to 50µg/m3.

(c) For the purpose of determiningattainment of the primary and sec-ondary standards, particulate mattershall be measured in the ambient air asPM10 (particles with an aerodynamicdiameter less than or equal to a nomi-nal 10 micrometers) by:

(1) A reference method based on ap-pendix J and designated in accordancewith part 53 of this chapter, or

(2) An equivalent method designatedin accordance with part 53 of this chap-ter.

[52 FR 24663, July 1, 1987, as amended at 62FR 38711, July 18, 1997; 65 FR 80779, Dec. 22,2000]

§ 50.7 National primary and secondaryambient air quality standards forparticulate matter.

(a) The national primary and sec-ondary ambient air quality standardsfor particulate matter are:

(1) 15.0 micrograms per cubic meter(µg/m3) annual arithmetic mean con-centration, and 65 µg/m3 24-hour aver-age concentration measured in the am-bient air as PM2.5 (particles with anaerodynamic diameter less than orequal to a nominal 2.5 micrometers) byeither:

(i) A reference method based on ap-pendix L of this part and designated inaccordance with part 53 of this chapter;or

(ii) An equivalent method designatedin accordance with part 53 of this chap-ter.


8

40 CFR Ch. I (7–1–01 Edition)§ 50.8

(2) 50 micrograms per cubic meter(µg/m3) annual arithmetic mean con-centration, and 150 µg/m3 24-hour aver-age concentration measured in the am-bient air as PM10 (particles with anaerodynamic diameter less than orequal to a nominal 10 micrometers) byeither:

(i) A reference method based on ap-pendix M of this part and designated inaccordance with part 53 of this chapter;or

(ii) An equivalent method designatedin accordance with part 53 of this chap-ter.

(b) The annual primary and sec-ondary PM2.5 standards are met whenthe annual arithmetic mean concentra-tion, as determined in accordance withappendix N of this part, is less than orequal to 15.0 micrograms per cubicmeter.

(c) The 24-hour primary and sec-ondary PM2.5 standards are met whenthe 98th percentile 24-hour concentra-tion, as determined in accordance withappendix N of this part, is less than orequal to 65 micrograms per cubicmeter.

(d) The annual primary and sec-ondary PM10 standards are met whenthe annual arithmetic mean concentra-tion, as determined in accordance withappendix N of this part, is less than orequal to 50 micrograms per cubicmeter.

(e) The 24-hour primary and sec-ondary PM10 standards are met whenthe 99th percentile 24-hour concentra-tion, as determined in accordance withappendix N of this part, is less than orequal to 150 micrograms per cubicmeter.

[62 FR 38711, July 18, 1997]

§ 50.8 National primary ambient airquality standards for carbon mon-oxide.

(a) The national primary ambient airquality standards for carbon monoxideare:

(1) 9 parts per million (10 milligramsper cubic meter) for an 8-hour averageconcentration not to be exceeded morethan once per year and

(2) 35 parts per million (40 milligramsper cubic meter) for a 1-hour average

concentration not to be exceeded morethan once per year.

(b) The levels of carbon monoxide inthe ambient air shall be measured by:

(1) A reference method based on ap-pendix C and designated in accordancewith part 53 of this chapter, or


(c) An 8-hour average shall be consid-ered valid if at least 75 percent of thehourly average for the 8-hour periodare available. In the event that onlysix (or seven) hourly averages areavailable, the 8-hour average shall becomputed on the basis of the hoursavailable using six (or seven) as the di-visor.

(d) When summarizing data forcomparision with the standards, aver-ages shall be stated to one decimalplace. Comparison of the data with thelevels of the standards in parts per mil-lion shall be made in terms of integerswith fractional parts of 0.5 or greaterrounding up.

[50 FR 37501, Sept. 13, 1985]

§ 50.9 National 1-hour primary andsecondary ambient air qualitystandards for ozone.

(a) The level of the national 1-hourprimary and secondary ambient airquality standards for ozone measuredby a reference method based on appen-dix D to this part and designated in ac-cordance with part 53 of this chapter, is0.12 parts per million (235 µg/m3). Thestandard is attained when the expectednumber of days per calendar year withmaximum hourly average concentra-tions above 0.12 parts per million (235µg/m3) is equal to or less than 1, as de-termined by appendix H to this part.

(b) The 1-hour standards set forth inthis section will remain applicable toall areas notwithstanding the promul-gation of 8-hour ozone standards under§ 50.10. In addition, after the 8-hourstandard has become fully enforceableunder part D of title I of the CAA andsubject to no further legal challenge,the 1-hour standards set forth in thissection will no longer apply to an areaonce EPA determines that the area has


9

Environmental Protection Agency Pt. 50, App. A

air quality meeting the 1-hour stand-ard. Area designations and classifica-tions with respect to the 1-hour stand-ards are codified in 40 CFR part 81.

[62 FR 38894, July 18, 1997, as amended at 65FR 45200, July 20, 2000]

§ 50.10 National 8-hour primary andsecondary ambient air qualitystandards for ozone.

(a) The level of the national 8-hourprimary and secondary ambient airquality standards for ozone, measuredby a reference method based on appen-dix D to this part and designated in ac-cordance with part 53 of this chapter, is0.08 parts per million (ppm), daily max-imum 8-hour average.

(b) The 8-hour primary and secondaryozone ambient air quality standardsare met at an ambient air quality mon-itoring site when the average of the an-nual fourth-highest daily maximum 8-hour average ozone concentration isless than or equal to 0.08 ppm, as deter-mined in accordance with appendix I tothis part.

[62 FR 38894, July 18, 1997]

§ 50.11 National primary and sec-ondary ambient air quality stand-ards for nitrogen dioxide.

(a) The level of the national primaryambient air quality standard for nitro-gen dioxide is 0.053 parts per million(100 micrograms per cubic meter), an-nual arithmetic mean concentration.

(b) The level of national secondaryambient air quality standard for nitro-gen dioxide is 0.053 parts per million(100 micrograms per cubic meter), an-nual arithmetic mean concentration.

(c) The levels of the standards shallbe measured by:

(1) A reference method based on ap-pendix F and designated in accordancewith part 53 of this chapter, or


(d) The standards are attained whenthe annual arithmetic mean concentra-tion in a calendar year is less than orequal to 0.053 ppm, rounded to threedecimal places (fractional parts equalto or greater than 0.0005 ppm must berounded up). To demonstrate attain-ment, an annual mean must be basedupon hourly data that are at least 75

percent complete or upon data derivedfrom manual methods that are at least75 percent complete for the scheduledsampling days in each calendar quar-ter.

[50 FR 25544, June 19, 1985]

§ 50.12 National primary and sec-ondary ambient air quality stand-ards for lead.

National primary and secondary am-bient air quality standards for lead andits compounds, measured as elementallead by a reference method based onappendix G to this part, or by an equiv-alent method, are: 1.5 micrograms percubic meter, maximum arithmeticmean averaged over a calendar quarter.

(Secs. 109, 301(a) Clean Air Act as amended(42 U.S.C. 7409, 7601(a)))

[43 FR 46258, Oct. 5, 1978]

APPENDIX A TO PART 50—REFERENCEMETHOD FOR THE DETERMINATION OFSULFUR DIOXIDE IN THE ATMOS-PHERE (PARAROSANILINE METHOD)

1.0 Applicability.1.1 This method provides a measurement of

the concentration of sulfur dioxide (SO2) inambient air for determining compliance withthe primary and secondary national ambientair quality standards for sulfur oxides (sulfurdioxide) as specified in § 50.4 and § 50.5 of thischapter. The method is applicable to themeasurement of ambient SO2 concentrationsusing sampling periods ranging from 30 min-utes to 24 hours. Additional quality assur-ance procedures and guidance are provided inpart 58, appendixes A and B, of this chapterand in references 1 and 2.

2.0 Principle.2.1 A measured volume of air is bubbled

through a solution of 0.04 M potassiumtetrachloromercurate (TCM). The SO2

present in the air stream reacts with theTCM solution to form a stable monochloro-sulfonatomercurate(3) complex. Onceformed, this complex resists air oxidation(4,5) and is stable in the presence of strongoxidants such as ozone and oxides of nitro-gen. During subsequent analysis, the com-plex is reacted with acid-bleached para-rosaniline dye and formaldehyde to form anintensely colored pararosaniline methyl sul-fonic acid.(6) The optical density of this spe-cies is determined spectrophotometrically at548 nm and is directly related to the amountof SO2 collected. The total volume of airsampled, corrected to EPA reference condi-tions (25 °C, 760 mm Hg [101 kPa]), is deter-mined from the measured flow rate and thesampling time. The concentration of SO2 in


10

40 CFR Ch. I (7–1–01 Edition)Pt. 50, App. A

the ambient air is computed and expressed inmicrograms per standard cubic meter (µg/stdm3).

3.0 Range.3.1 The lower limit of detection of SO2 in 10

mL of TCM is 0.75 µg (based on collaborativetest results).(7) This represents a concentra-tion of 25 µg SO2/m3 (0.01 ppm) in an air sam-ple of 30 standard liters (short-term sam-pling) and a concentration of 13 µg SO2/m3

(0.005 ppm) in an air sample of 288 standardliters (long-term sampling). Concentrationsless than 25 µg SO2/m3 can be measured bysampling larger volumes of ambient air;however, the collection efficiency falls offrapidly at low concentrations.(8, 9) Beer’slaw is adhered to up to 34 µg of SO2 in 25 mLof final solution. This upper limit of theanalysis range represents a concentration of1,130 µg SO2/m3 (0.43 ppm) in an air sample of30 standard liters and a concentration of 590µg SO2/m3 (0.23 ppm) in an air sample of 288standard liters. Higher concentrations can bemeasured by collecting a smaller volume ofair, by increasing the volume of absorbingsolution, or by diluting a suitable portion ofthe collected sample with absorbing solutionprior to analysis.

4.0 Interferences.4.1 The effects of the principal potential

interferences have been minimized or elimi-nated in the following manner: Nitrogen ox-ides by the addition of sulfamic acid,(10, 11)heavy metals by the addition of ethylene-diamine tetracetic acid disodium salt(EDTA) and phosphoric acid,(10, 12) andozone by time delay.(10) Up to 60 µg Fe (III),22 µg V (V), 10 µg Cu (II), 10 µg Mn (II), and10 µg Cr (III) in 10 mL absorbing reagent canbe tolerated in the procedure.(10) No signifi-cant interference has been encountered with2.3 µg NH3.(13)

5.0 Precision and Accuracy.5.1 The precision of the analysis is 4.6 per-

cent (at the 95 percent confidence level)based on the analysis of standard sulfitesamples.(10)

5.2 Collaborative test results (14) based onthe analysis of synthetic test atmospheres(SO2 in scrubbed air) using the 24-hour sam-pling procedure and the sulfite-TCM calibra-tion procedure show that:

• The replication error varies linearly withconcentration from ±2.5 µg/m3 at con-centrations of 100 µg/m3 to ±7 µg/m3 at con-centrations of 400 µg/m3.

• The day-to-day variability within an indi-vidual laboratory (repeatability) varieslinearly with concentration from ±18.1 µg/m3 at levels of 100 µg/m3 to ±50.9 µg/m3 atlevels of 400 µg/m3.

• The day-to-day variability between two ormore laboratories (reproducibility) varieslinearly with concentration from ±36.9 µg/m3 at levels of 100 µg/m3 to ±103.5 µ g/m3 atlevels of 400 µg/m3.

• The method has a concentration-dependentbias, which becomes significant at the 95percent confidence level at the high con-centration level. Observed values tend tobe lower than the expected SO2 concentra-tion level.6.0 Stability.6.1 By sampling in a controlled tempera-

ture environment of 15°±10 °C, greater than98.9 percent of the SO2–TCM complex is re-tained at the completion of sampling. (15) Ifkept at 5 °C following the completion of sam-pling, the collected sample has been found tobe stable for up to 30 days.(10) The presenceof EDTA enhances the stability of SO2 in theTCM solution and the rate of decay is inde-pendent of the concentration of SO2.(16)

7.0 Apparatus.7.1 Sampling.7.1.1 Sample probe: A sample probe meeting

the requirements of section 7 of 40 CFR part58, appendix E (Teflon or glass with resi-dence time less than 20 sec.) is used to trans-port ambient air to the sampling train loca-tion. The end of the probe should be designedor oriented to preclude the sampling of pre-cipitation, large particles, etc. A suitableprobe can be constructed from Teflon tub-ing connected to an inverted funnel.

7.1.2 Absorber—short-term sampling: An allglass midget impinger having a solution ca-pacity of 30 mL and a stem clearance of 4±1mm from the bottom of the vessel is used forsampling periods of 30 minutes and 1 hour (orany period considerably less than 24 hours).Such an impinger is shown in Figure 1. Theseimpingers are commercially available fromdistributors such as Ace Glass, Incorporated.

7.1.3 Absorber—24-hour sampling: A poly-propylene tube 32 mm in diameter and 164mm long (available from Bel Art Products,Pequammock, NJ) is used as the absorber.The cap of the absorber must be a poly-propylene cap with two ports (rubber stop-pers are unacceptable because the absorbingreagent can react with the stopper to yielderroneously high SO2 concentrations). Aglass impinger stem, 6 mm in diameter and158 mm long, is inserted into one port of theabsorber cap. The tip of the stem is taperedto a small diameter orifice (0.4±0.1 mm) suchthat a No. 79 jeweler’s drill bit will passthrough the opening but a No. 78 drill bitwill not. Clearance from the bottom of theabsorber to the tip of the stem must be 6±2mm. Glass stems can be fabricated by anyreputable glass blower or can be obtainedfrom a scientific supply firm. Upon receipt,the orifice test should be performed to verifythe orifice size. The 50 mL volume levelshould be permanently marked on the ab-sorber. The assembled absorber is shown inFigure 2.

7.1.4 Moisture trap: A moisture trap con-structed of a glass trap as shown in Figure 1or a polypropylene tube as shown in Figure2 is placed between the absorber tube and


11


flow control device to prevent entrained liq-uid from reaching the flow control device.The tube is packed with indicating silica gelas shown in Figure 2. Glass wool may be sub-stituted for silica gel when collecting short-term samples (1 hour or less) as shown inFigure 1, or for long term (24 hour) samples

if flow changes are not routinely encoun-tered.

7.1.5 Cap seals: The absorber and moisturetrap caps must seal securely to prevent leaksduring use. Heat-shrink material as shown inFigure 2 can be used to retain the cap sealsif there is any chance of the caps comingloose during sampling, shipment, or storage.


12



13


7.1.6 Flow control device: A calibrated ro-tameter and needle valve combination capa-ble of maintaining and measuring air flow towithin ±2 percent is suitable for short-termsampling but may not be used for long-termsampling. A critical orifice can be used forregulating flow rate for both long-term andshort-term sampling. A 22-gauge hypodermicneedle 25 mm long may be used as a criticalorifice to yield a flow rate of approximately1 L/min for a 30-minute sampling period.When sampling for 1 hour, a 23-gauge hypo-dermic needle 16 mm in length will provide aflow rate of approximately 0.5 L/min. Flowcontrol for a 24-hour sample may be providedby a 27-gauge hypodermic needle critical ori-fice that is 9.5 mm in length. The flow rateshould be in the range of 0.18 to 0.22 L/min.

7.1.7 Flow measurement device: Device cali-brated as specified in 9.4.1 and used to meas-ure sample flow rate at the monitoring site.

7.1.8 Membrane particle filter: A membranefilter of 0.8 to 2 µm porosity is used to pro-tect the flow controller from particles dur-ing long-term sampling. This item is op-tional for short-term sampling.

7.1.9 Vacuum pump: A vacuum pumpequipped with a vacuum gauge and capableof maintaining at least 70 kPa (0.7 atm) vac-uum differential across the flow control de-vice at the specified flow rate is required forsampling.

7.1.10 Temperature control device: The tem-perature of the absorbing solution duringsampling must be maintained at 15° ±10 °C.As soon as possible following sampling anduntil analysis, the temperature of the col-lected sample must be maintained at 5° ±5 °C.Where an extended period of time may elapsebefore the collected sample can be moved tothe lower storage temperature, a collectiontemperature near the lower limit of the 15 ±10 °C range should be used to minimize lossesduring this period. Thermoelectric coolersspecifically designed for this temperaturecontrol are available commercially and nor-mally operate in the range of 5° to 15 °C.Small refrigerators can be modified to pro-vide the required temperature control; how-ever, inlet lines must be insulated from thelower temperatures to prevent condensationwhen sampling under humid conditions. Asmall heating pad may be necessary whensampling at low temperatures (<7 °C) to pre-vent the absorbing solution from freez-ing.(17)

7.1.11 Sampling train container: The absorb-ing solution must be shielded from light dur-ing and after sampling. Most commerciallyavailable sampler trains are enclosed in alight-proof box.

7.1.12 Timer: A timer is recommended toinitiate and to stop sampling for the 24-hourperiod. The timer is not a required piece ofequipment; however, without the timer atechnician would be required to start andstop the sampling manually. An elapsed time

meter is also recommended to determine theduration of the sampling period.

7.2 Shipping.7.2.1 Shipping container: A shipping con-

tainer that can maintain a temperature of 5°±5 °C is used for transporting the samplefrom the collection site to the analyticallaboratory. Ice coolers or refrigerated ship-ping containers have been found to be satis-factory. The use of eutectic cold packs in-stead of ice will give a more stable tempera-ture control. Such equipment is availablefrom Cole-Parmer Company, 7425 North OakPark Avenue, Chicago, IL 60648.

7.3 Analysis.7.3.1 Spectrophotometer: A spectrophotom-

eter suitable for measurement of absorb-ances at 548 nm with an effective spectralbandwidth of less than 15 nm is required foranalysis. If the spectrophotometer reads outin transmittance, convert to absorbance asfollows:

A T= log ( / ) ( )10 1 1where:

A = absorbance, andT = transmittance (0<´T<1).

A standard wavelength filter traceable tothe National Bureau of Standards is used toverify the wavelength calibration accordingto the procedure enclosed with the filter.The wavelength calibration must be verifiedupon initial receipt of the instrument andafter each 160 hours of normal use or every 6months, whichever occurs first.

7.3.2 Spectrophotometer cells: A set of 1-cmpath length cells suitable for use in the visi-ble region is used during analysis. If the cellsare unmatched, a matching correction factormust be determined according to Section10.1.

7.3.3 Temperature control device: The colordevelopment step during analysis must beconducted in an environment that is in therange of 20° to 30 °C and controlled to ±1 °C.Both calibration and sample analysis mustbe performed under identical conditions(within 1 °C). Adequate temperature controlmay be obtained by means of constant tem-perature baths, water baths with manualtemperature control, or temperature con-trolled rooms.

7.3.4 Glassware: Class A volumetric glass-ware of various capacities is required for pre-paring and standardizing reagents and stand-ards and for dispensing solutions duringanalysis. These included pipets, volumetricflasks, and burets.

7.3.5 TCM waste receptacle: A glass waste re-ceptacle is required for the storage of spentTCM solution. This vessel should bestoppered and stored in a hood at all times.

8.0 Reagents.8.1 Sampling.


14


8.1.1 Distilled water: Purity of distilledwater must be verified by the following pro-cedure:(18)• Place 0.20 mL of potassium permanganate

solution (0.316 g/L), 500 mL of distilledwater, and 1mL of concentrated sulfuricacid in a chemically resistant glass bottle,stopper the bottle, and allow to stand.

• If the permanganate color (pink) does notdisappear completely after a period of 1hour at room temperature, the water issuitable for use.

• If the permanganate color does disappear,the water can be purified by redistillingwith one crystal each of barium hydroxideand potassium permanganate in an allglass still.

8.1.2 Absorbing reagent (0.04 M potassiumtetrachloromercurate [TCM]): Dissolve 10.86g mercuric chloride, 0.066 g EDTA, and 6.0 gpotassium chloride in distilled water and di-lute to volume with distilled water in a 1,000-mL volumetric flask. (Caution: Mercuricchloride is highly poisonous. If spilled onskin, flush with water immediately.) The pHof this reagent should be between 3.0 and 5.0(10) Check the pH of the absorbing solutionby using pH indicating paper or a pH meter.If the pH of the solution is not between 3.0and 5.0, dispose of the solution according toone of the disposal techniques described inSection 13.0. The absorbing reagent is nor-mally stable for 6 months. If a precipitateforms, dispose of the reagent according toone of the procedures described in Section13.0.

8.2 Analysis.8.2.1 Sulfamic acid (0.6%): Dissolve 0.6 g sul-

famic acid in 100 mL distilled water. Perparefresh daily.

8.2.2 Formaldehyde (0.2%): Dilute 5 mLformaldehyde solution (36 to 38 percent) to1,000 mL with distilled water. Prepare freshdaily.

8.2.3 Stock iodine solution (0.1 N): Place 12.7g resublimed iodine in a 250-mL beaker andadd 40 g potassium iodide and 25 mL water.Stir until dissolved, transfer to a 1,000 mLvolumetric flask and dilute to volume withdistilled water.

8.2.4 Iodine solution (0.01 N): Prepare ap-proximately 0.01 N iodine solution by dilut-ing 50 mL of stock iodine solution (Section8.2.3) to 500 mL with distilled water.

8.2.5 Starch indicator solution: Triturate 0.4g soluble starch and 0.002 g mercuric iodide(preservative) with enough distilled water toform a paste. Add the paste slowly to 200 mLof boiling distilled water and continue boil-ing until clear. Cool and transfer the solu-tion to a glass stopperd bottle.

8.2.6 1 N hydrochloric acid: Slowly and whilestirring, add 86 mL of concentrated hydro-chloric acid to 500 mL of distilled water.Allow to cool and dilute to 1,000 mL with dis-tilled water.

8.2.7 Potassium iodate solution: Accuratelyweigh to the nearest 0.1 mg, 1.5 g (recordweight) of primary standard grade potassiumiodate that has been previously dried at 180°C for at least 3 hours and cooled in adessicator. Dissolve, then dilute to volume ina 500-mL volumetric flask with distilledwater.

8.2.8 Stock sodium thiosulfate solution (0.1 N):Prepare a stock solution by dissolving 25 gsodium thiosulfate (Na2 S2 O3÷5H2 O) in 1,000mL freshly boiled, cooled, distilled water andadding 0.1 g sodium carbonate to the solu-tion. Allow the solution to stand at least 1day before standardizing. To standardize, ac-curately pipet 50 mL of potassium iodate so-lution (Section 8.2.7) into a 500-mL iodineflask and add 2.0 g of potassium iodide and 10mL of 1 N HCl. Stopper the flask and allowto stand for 5 minutes. Titrate the solutionwith stock sodium thiosulfate solution (Sec-tion 8.2.8) to a pale yellow color. Add 5 mL ofstarch solution (Section 8.2.5) and titrateuntil the blue color just disappears. Cal-culate the normality (Ns) of the stock so-dium thiosulfate solution as follows:

NW

MS = ×2 80 2. ( )

where:M = volume of thiosulfate required in mL,

andW = weight of potassium iodate in g (re-

corded weight in Section 8.2.7).

2 8010 0 1

35 67

3

.( ) . ( )

. ( )= ×conversion of g to mg fraction iodate used

equivalent weight of potassium iodate

8.2.9 Working sodium thiosulfate titrant (0.01N): Accurately pipet 100 mL of stock sodiumthiosulfate solution (Section 8.2.8) into a1,000-mL volumetric flask and dilute to vol-ume with freshly boiled, cooled, distilledwater. Calculate the normality of the work-ing sodium thiosulfate titrant (NT) as fol-lows:

N NT S= ×0 100 3. ( )8.2.10 Standardized sulfite solution for the

preparation of working sulfite-TCM solution:Dissolve 0.30 g sodium metabisulfite (Na2 S2

O5) or 0.40 g sodium sulfite (Na2 SO3) in 500mL of recently boiled, cooled, distilledwater. (Sulfite solution is unstable; it istherefore important to use water of the high-est purity to minimize this instability.) Thissolution contains the equivalent of 320 to 400µg SO2/mL. The actual concentration of thesolution is determined by adding excess io-dine and back-titrating with standard so-dium thiosulfate solution. To back-titrate,pipet 50 mL of the 0.01 N iodine solution(Section 8.2.4) into each of two 500-mL iodineflasks (A and B). To flask A (blank) add 25mL distilled water, and to flask B (sample)


15


pipet 25 mL sulfite solution. Stopper theflasks and allow to stand for 5 minutes. Pre-pare the working sulfite-TCM solution (Sec-tion 8.2.11) immediately prior to adding theiodine solution to the flasks. Using a buretcontaining standardized 0.01 N thiosulfatetitrant (Section 8.2.9), titrate the solution ineach flask to a pale yellow color. Then add 5mL starch solution (Section 8.2.5) and con-

tinue the titration until the blue color justdisappears.

8.2.11 Working sulfite-TCM solution: Accu-rately pipet 5 mL of the standard sulfite so-lution (Section 8.2.10) into a 250-mL volu-metric flask and dilute to volume with 0.04M TCM. Calculate the concentration of sul-fur dioxide in the working solution as fol-lows:

C gSO mLA B N

TCM SOT

/ /( ) ( , )

. ( )2 2

32 000

250 02 4µ( ) =

− ( )×

where:A = volume of thiosulfate titrant required

for the blank, mL;B = volume of thiosulfate titrant required

for the sample, mL;NT = normality of the thiosulfate titrant,

from equation (3);32,000 = milliequivalent weight of SO2, µg;25 = volume of standard sulfite solution, mL;

and0.02 = dilution factor.

This solution is stable for 30 days if kept at5 °C. (16) If not kept at 5 °C, prepare freshdaily.

8.2.12 Purified pararosaniline (PRA) stock so-lution (0.2% nominal):

8.2.12.1 Dye specifications—• The dye must have a maximum absorbance

at a wavelength of 540 nm when assayed ina buffered solution of 0.1 M sodium ace-tate-acetic acid;

• The absorbance of the reagent blank,which is temperature sensitive (0.015 ab-sorbance unit/ °C), must not exceed 0.170 at22 °C with a 1-cm optical path length whenthe blank is prepared according to thespecified procedure;

• The calibration curve (Section 10.0) musthave a slope equal to 0.030±0.002 absorbanceunit/µg SO2 with a 1-cm optical path lengthwhen the dye is pure and the sulfite solu-tion is properly standardized.8.2.12.2 Preparation of stock PRA solution— A

specially purified (99 to 100 percent pure) so-lution of pararosaniline, which meets theabove specifications, is commercially avail-able in the required 0.20 percent concentra-tion (Harleco Co.). Alternatively, the dyemay be purified, a stock solution prepared,and then assayed according to the procedureas described below.(10)

8.2.12.3 Purification procedure for PRA—1. Place 100 mL each of 1-butanol and 1 N

HCl in a large separatory funnel (250-mL)and allow to equilibrate. Note: Certainbatches of 1-butanol contain oxidants thatcreate an SO2 demand. Before using, checkby placing 20 mL of 1-butanol and 5 mL of 20

percent potassium iodide (KI) solution in a50-mL separatory funnel and shake thor-oughly. If a yellow color appears in the alco-hol phase, redistill the 1-butanol from silveroxide and collect the middle fraction or pur-chase a new supply of 1-butanol.

2. Weigh 100 mg of pararosaniline hydro-chloride dye (PRA) in a small beaker. Add 50mL of the equilibrated acid (drain in acidfrom the bottom of the separatory funnel in1.) to the beaker and let stand for severalminutes. Discard the remaining acid phase inthe separatory funnel.

3. To a 125-mL separatory funnel, add 50mL of the equilibrated 1-butanol (draw the 1-butanol from the top of the separatory fun-nel in 1.). Transfer the acid solution (from 2.)containing the dye to the funnel and shakecarefully to extract. The violet impurity willtransfer to the organic phase.

4. Transfer the lower aqueous phase intoanother separatory funnel, add 20 mL ofequilibrated 1-butanol, and extract again.

5. Repeat the extraction procedure withthree more 10-mL portions of equilibrated 1-butanol.

6. After the final extraction, filter the acidphase through a cotton plug into a 50-mLvolumetric flask and bring to volume with 1N HCl. This stock reagent will be a yellowishred.

7. To check the purity of the PRA, performthe assay and adjustment of concentration(Section 8.2.12.4) and prepare a reagent blank(Section 11.2); the absorbance of this reagentblank at 540 nm should be less than 0.170 at22 °C. If the absorbance is greater than 0.170under these conditions, further extractionsshould be performed.

8.2.12.4 PRA assay procedure— The con-centration of pararosaniline hydrochloride(PRA) need be assayed only once after purifi-cation. It is also recommended that commer-cial solutions of pararosaniline be assayedwhen first purchased. The assay procedure isas follows:(10)

1. Prepare 1 M acetate-acetic acid bufferstock solution with a pH of 4.79 by dissolving


16


13.61 g of sodium acetate trihydrate in dis-tilled water in a 100-mL volumetric flask.Add 5.70 mL of glacial acetic acid and diluteto volume with distilled water.

2. Pipet 1 mL of the stock PRA solution ob-tained from the purification process or froma commercial source into a 100-mL volu-metric flask and dilute to volume with dis-tilled water.

3. Transfer a 5–mL aliquot of the dilutedPRA solution from 2. into a 50–mL volu-metric flask. Add 5mL of 1 M acetate-aceticacid buffer solution from 1. and dilute themixture to volume with distilled water. Letthe mixture stand for 1 hour.

4. Measure the absorbance of the above so-lution at 540 nm with a spectrophotometeragainst a distilled water reference. Computethe percentage of nominal concentration ofPRA by

% ( )PRAA K

W=

×5

where:

A = measured absorbance of the final mix-ture (absorbance units);

W = weight in grams of the PRA dye used inthe assay to prepare 50 mL of stock solu-tion (for example, 0.100 g of dye was used toprepare 50 mL of solution in the purifi-cation procedure; when obtained from com-mercial sources, use the stated concentra-tion to compute W; for 98% PRA, W=.098g.); and

K = 21.3 for spectrophotometers having aspectral bandwidth of less than 15 nm anda path length of 1 cm.

8.2.13 Pararosaniline reagent: To a 250–mLvolumetric flask, add 20 mL of stock PRA so-lution. Add an additional 0.2 mL of stock so-lution for each percentage that the stock as-says below 100 percent. Then add 25 mL of 3M phosphoric acid and dilute to volume withdistilled water. The reagent is stable for atleast 9 months. Store away from heat andlight.

9.0 Sampling Procedure.9.1 General Considerations. Procedures are

described for short-term sampling (30-minuteand 1-hour) and for long-term sampling (24-hour). Different combinations of absorbingreagent volume, sampling rate, and samplingtime can be selected to meet special needs.For combinations other than those specifi-

cally described, the conditions must be ad-justed so that linearity is maintained be-tween absorbance and concentration over thedynamic range. Absorbing reagent volumesless than 10 mL are not recommended. Thecollection efficiency is above 98 percent forthe conditions described; however, the effi-ciency may be substantially lower whensampling concentrations below 25µγSO2/m3.(8,9)

9.2 30-Minute and 1-Hour Sampling. Place 10mL of TCM absorbing reagent in a midgetimpinger and seal the impinger with a thinfilm of silicon stopcock grease (around theground glass joint). Insert the sealed im-pinger into the sampling train as shown inFigure 1, making sure that all connectionsbetween the various components are leaktight. Greaseless ball joint fittings, heatshrinkable Teflon tubing, or Teflon tubefittings may be used to attain leakfree con-ditions for portions of the sampling trainthat come into contact with air containingSO2. Shield the absorbing reagent from di-rect sunlight by covering the impinger withaluminum foil or by enclosing the samplingtrain in a light-proof box. Determine theflow rate according to Section 9.4.2. Collectthe sample at 1±0.10 L/min for 30-minutesampling or 0.500±0.05 L/min for 1-hour sam-pling. Record the exact sampling time inminutes, as the sample volume will later bedetermined using the sampling flow rate andthe sampling time. Record the atmosphericpressure and temperature.

9.3 24-Hour Sampling. Place 50 mL of TCMabsorbing solution in a large absorber, closethe cap, and, if needed, apply the heat shrinkmaterial as shown in Figure 3. Verify thatthe reagent level is at the 50 mL mark on theabsorber. Insert the sealed absorber into thesampling train as shown in Figure 2. At thistime verify that the absorber temperature iscontrolled to 15±10 °C. During sampling, theabsorber temperature must be controlled toprevent decomposition of the collected com-plex. From the onset of sampling until anal-ysis, the absorbing solution must be pro-tected from direct sunlight. Determine theflow rate according to Section 9.4.2. Collectthe sample for 24 hours from midnight tomidnight at a flow rate of 0.200±0.020 L/min.A start/stop timer is helpful for initiatingand stopping sampling and an elapsed timemeter will be useful for determining thesampling time.


17


9.4 Flow Measurement.9.4.1 Calibration: Flow measuring devices

used for the on-site flow measurements re-quired in 9.4.2 must be calibrated against areliable flow or volume standard such as anNBS traceable bubble flowmeter or cali-brated wet test meter. Rotameters or crit-ical orifices used in the sampling train maybe calibrated, if desired, as a quality controlcheck, but such calibration shall not replacethe on-site flow measurements required by9.4.2. In-line rotameters, if they are to becalibrated, should be calibrated in situ, withthe appropriate volume of solution in the ab-sorber.

9.4.2 Determination of flow rate at samplingsite: For short-term samples, the standardflow rate is determined at the sampling siteat the initiation and completion of samplecollection with a calibrated flow measuringdevice connected to the inlet of the absorber.

For 24-hour samples, the standard flow rateis determined at the time the absorber isplaced in the sampling train and again whenthe absorber is removed from the train forshipment to the analytical laboratory with acalibrated flow measuring device connectedto the inlet of the sampling train. The flowrate determination must be made with allcomponents of the sampling system in oper-ation (e.g., the absorber temperature con-troller and any sample box heaters must alsobe operating). Equation 6 may be used to de-termine the standard flow rate when a cali-brated positive displacement meter is usedas the flow measuring device. Other types ofcalibrated flow measuring devices may alsobe used to determine the flow rate at thesampling site provided that the user appliesany appropriate corrections to devices forwhich output is dependent on temperature orpressure.


18


Q QP RH P

P Tstd actb H O

std meter

= ×− −

×+( )

( ) . .

. .( )

1 29816

2731662

where:

Qstd = flow rate at standard conditions, std L/min (25 °C and 760 mm Hg);

Qact = flow rate at monitoring site conditions,L/min;

Pb = barometric pressure at monitoring siteconditions, mm Hg or kPa;

RH = fractional relative humidity of the airbeing measured;

PH2O = vapor pressure of water at the tem-perature of the air in the flow or volumestandard, in the same units as Pb, (for wet

volume standards only, i.e., bubble flow-meter or wet test meter; for dry standards,i.e., dry test meter, PH2O=0);

Pstd = standard barometric pressure, in thesame units as Pb (760 mm Hg or 101 kPa);and

Tmeter = temperature of the air in the flow orvolume standard, °C (e.g., bubble flow-meter).

If a barometer is not available, the fol-lowing equation may be used to determinethe barometric pressure:

P H mm Hg or P H kPab b= − = −760 076 101 01 7. ( ) , . ( ) ( )

where:

H = sampling site elevation above sea levelin meters.

If the initial flow rate (Qi) differs from theflow rate of the critical orifice or the flowrate indicated by the flowmeter in the sam-pling train (Qc) by more than 5 percent as de-termined by equation (8), check for leaks andredetermine Qi.

% ( ) DiffQ Q

Q

i c

c

=−

×100 8

Invalidate the sample if the difference be-tween the initial (Qi) and final (Qf) flow ratesis more than 5 percent as determined byequation (9):

% ( ) DiffQ Q

Qi f

f

=−

×100 9

9.5 Sample Storage and Shipment. Removethe impinger or absorber from the samplingtrain and stopper immediately. Verify thatthe temperature of the absorber is not above25 °C. Mark the level of the solution with atemporary (e.g., grease pencil) mark. If thesample will not be analyzed within 12 hoursof sampling, it must be stored at 5° ±5 °Cuntil analysis. Analysis must occur within 30days. If the sample is transported or shippedfor a period exceeding 12 hours, it is rec-ommended that thermal coolers usingeutectic ice packs, refrigerated shipping con-tainers, etc., be used for periods up to 48hours. (17) Measure the temperature of theabsorber solution when the shipment is re-ceived. Invalidate the sample if the tempera-

ture is above 10 °C. Store the sample at 5° ±5°C until it is analyzed.

10.0 Analytical Calibration.10.1 Spectrophotometer Cell Matching. If un-

matched spectrophotometer cells are used,an absorbance correction factor must be de-termined as follows:

1. Fill all cells with distilled water and des-ignate the one that has the lowest absorb-ance at 548 nm as the reference. (This ref-erence cell should be marked as such andcontinually used for this purpose throughoutall future analyses.)

2. Zero the spectrophotometer with the ref-erence cell.

3. Determine the absorbance of the remain-ing cells (Ac) in relation to the reference celland record these values for future use. Markall cells in a manner that adequately identi-fies the correction.

The corrected absorbance during futureanalyses using each cell is determining asfollows:

A A Aobs c= − ( )10where:A = corrected absorbance,Aobs = uncorrected absorbance, andAc = cell correction.

10.2 Static Calibration Procedure (Option 1).Prepare a dilute working sulfite-TCM solu-tion by diluting 10 mL of the working sul-fite-TCM solution (Section 8.2.11) to 100 mLwith TCM absorbing reagent. Following thetable below, accurately pipet the indicatedvolumes of the sulfite-TCM solutions into aseries of 25-mL volumetric flasks. Add TCMabsorbing reagent as indicated to bring thevolume in each flask to 10 mL.


19


Sulfite-TCM solution

Volumeof sulfite-TCM so-

lution

Volumeof TCM,

mL

Total µgSO2

(approx.*

Working ......................... 4.0 6.0 28.8Working ......................... 3.0 7.0 21.6Working ......................... 2.0 8.0 14.4Dilute working ................ 10.0 0.0 7.2Dilute working ................ 5.0 5.0 3.6

0.0 10.0 0.0

*Based on working sulfite-TCM solution concentration of 7.2µg SO2/mL; the actual total µg SO2 must be calculated usingequation 11 below.

To each volumetric flask, add 1 mL 0.6%sulfamic acid (Section 8.2.1), accuratelypipet 2 mL 0.2% formaldehyde solution (Sec-tion 8.2.2), then add 5 mL pararosaniline so-lution (Section 8.2.13). Start a laboratory

timer that has been set for 30 minutes. Bringall flasks to volume with recently boiled andcooled distilled water and mix thoroughly.The color must be developed (during the 30-minute period) in a temperature environ-ment in the range of 20° to 30 °C, which iscontrolled to ±1 °C. For increased precision,a constant temperature bath is rec-ommended during the color developmentstep. After 30 minutes, determine the cor-rected absorbance of each standard at 548 nmagainst a distilled water reference (Section10.1). Denote this absorbance as (A). Distilledwater is used in the reference cell ratherthan the reagant blank because of the tem-perature sensitivity of the reagent blank.Calculate the total micrograms SO2 in eachsolution:

µg SO V C DTCM SO TCM SO 2 22 11= × ×/ / ( )

where:VTCM/SO2 = volume of sulfite-TCM solution

used, mL;CTCM/SO2 = concentration of sulfur dioxide in

the working sulfite-TCM, µg SO2/mL (fromequation 4); and

D = dilution factor (D = 1 for the workingsulfite-TCM solution; D = 0.1 for the di-luted working sulfite-TCM solution).

A calibration equation is determined usingthe method of linear least squares (Section12.1). The total micrograms SO2 contained ineach solution is the x variable, and the cor-rected absorbance (eq. 10) associated witheach solution is the y variable. For the cali-bration to be valid, the slope must be in therange of 0.030 ±0.002 absorbance unit/µg SO2,

the intercept as determined by the leastsquares method must be equal to or less than0.170 absorbance unit when the color is devel-oped at 22 °C (add 0.015 to this 0.170 specifica-tion for each °C above 22 °C) and the correla-tion coefficient must be greater than 0.998. Ifthese criteria are not met, it may be the re-sult of an impure dye and/or an improperlystandardized sulfite-TCM solution. A calibra-tion factor (Bs) is determined by calculatingthe reciprocal of the slope and is subse-quently used for calculating the sample con-centration (Section 12.3).

10.3 Dynamic Calibration Procedures (Option2). Atmospheres containing accuratelyknown concentrations of sulfur dioxide areprepared using permeation devices. In thesystems for generating these atmospheres,the permeation device emits gaseous SO2 ata known, low, constant rate, provided thetemperature of the device is held constant(±0.1 °C) and the device has been accuratelycalibrated at the temperature of use. TheSO2 permeating from the device is carried by

a low flow of dry carrier gas to a mixingchamber where it is diluted with SO2-free airto the desired concentration and supplied toa vented manifold. A typical system is shownschematically in Figure 4 and this systemand other similar systems have been de-scribed in detail by O’Keeffe and Ortman; (19)Scaringelli, Frey, and Saltzman, (20) andScaringelli, O’Keeffe, Rosenberg, and Bell.(21) Permeation devices may be prepared orpurchased and in both cases must be trace-able either to a National Bureau of Stand-ards (NBS) Standard Reference Material(SRM 1625, SRM 1626, SRM 1627) or to anNBS/EPA-approved commercially availableCertified Reference Material (CRM). CRM’sare described in Reference 22, and a list ofCRM sources is available from the addressshown for Reference 22. A recommended pro-tocol for certifying a permeation device toan NBS SRM or CRM is given in Section 2.0.7of Reference 2. Device permeation rates of 0.2to 0.4 µg/min, inert gas flows of about 50 mL/min, and dilution air flow rates from 1.1 to 15L/min conveniently yield standardatmospheres in the range of 25 to 600 µg SO2/m3 (0.010 to 0.230 ppm).

10.3.1 Calibration Option 2A (30-minute and1-hour samples): Generate a series of sixstandard atmospheres of SO2 (e.g., 0, 50, 100,200, 350, 500, 750 µg/m3) by adjusting the dilu-tion flow rates appropriately. The concentra-tion of SO2 in each atmosphere is calculatedas follows:

CP

Q Qa

r

d p

=×

+

1012

3

( )

where:


20


Ca = concentration of SO2 at standard condi-tions, µg/m3;

Pr = permeation rate, µg/min;

Qd = flow rate of dilution air, std L/min; andQp = flow rate of carrier gas across perme-

ation device, std L/min.


21


Be sure that the total flow rate of thestandard exceeds the flow demand of thesample train, with the excess flow vented atatmospheric pressure. Sample each atmos-phere using similar apparatus as shown inFigure 1 and under the same conditions asfield sampling (i.e., use same absorbing rea-gent volume and sample same volume of airat an equivalent flow rate). Due to thelength of the sampling periods required, thismethod is not recommended for 24-hour sam-pling. At the completion of sampling, quan-titatively transfer the contents of each im-pinger to one of a series of 25-mL volumetricflasks (if 10 mL of absorbing solution wasused) using small amounts of distilled waterfor rinse (<5mL). If >10 mL of absorbing solu-tion was used, bring the absorber solution ineach impinger to orginal volume with dis-tilled H2 O and pipet 10-mL portions fromeach impinger into a series of 25-mL volu-metric flasks. If the color development stepsare not to be started within 12 hours of sam-pling, store the solutions at 5° ± 5 °C. Cal-culate the total micrograms SO2 in each so-lution as follows:

µgSOC Q t V

Va s a

b2

31013=

× × × × −

( )

where:

Ca = concentration of SO2 in the standard at-mosphere, µg/m3 ;

Os = sampling flow rate, std L/min;t=sampling time, min;Va = volume of absorbing solution used for

color development (10 mL); andVb = volume of absorbing solution used for

sampling, mL.

Add the remaining reagents for color de-velopment in the same manner as in Section10.2 for static solutions. Calculate a calibra-tion equation and a calibration factor (Bg)according to Section 10.2, adhering to all thespecified criteria.

10.3.2 Calibration Option 2B (24-hour sam-ples): Generate a standard atmosphere con-taining approximately 1,050 µg SO2/m3 andcalculate the exact concentration accordingto equation 12. Set up a series of six absorb-ers according to Figure 2 and connect to acommon manifold for sampling the standardatmosphere. Be sure that the total flow rateof the standard exceeds the flow demand atthe sample manifold, with the excess flowvented at atmospheric pressure. The absorb-ers are then allowed to sample the atmos-phere for varying time periods to yield solu-tions containing 0, 0.2, 0.6, 1.0, 1.4, 1.8, and 2.2µg SO2/mL solution. The sampling times re-quired to attain these solution concentra-tions are calculated as follows:

tV C

C Q

b s

a s

=×

× ×−

1014

3( )

where:t = sampling time, min;Vb = volume of absorbing solution used for

sampling (50 mL);Cs = desired concentration of SO2 in the ab-

sorbing solution, µg/mL;Ca = concentration of the standard atmos-

phere calculated according to equation 12,µg/m3 ; and

Qs = sampling flow rate, std L/min.

At the completion of sampling, bring theabsorber solutions to original volume withdistilled water. Pipet a 10-mL portion fromeach absorber into one of a series of 25-mLvolumetric flasks. If the color developmentsteps are not to be started within 12 hours ofsampling, store the solutions at 5° ± 5 °C. Addthe remaining reagents for color develop-ment in the same manner as in Section 10.2for static solutions. Calculate the total µgSO2 in each standard as follows:

µgSOC Q t V

V

a s a

b

2

310

15=× × × ×

−

( )

where:Va = volume of absorbing solution used for

color development (10 mL).All other parameters are defined in equation

14.

Calculate a calibration equation and acalibration factor (Bt) according to Section10.2 adhering to all the specified criteria.

11.0 Sample Preparation and Analysis.11.1 Sample Preparation. Remove the sam-

ples from the shipping container. If the ship-ment period exceeded 12 hours from the com-pletion of sampling, verify that the tempera-ture is below 10 °C. Also, compare the solu-tion level to the temporary level mark onthe absorber. If either the temperature isabove 10 °C or there was significant loss(more than 10 mL) of the sample during ship-ping, make an appropriate notation in therecord and invalidate the sample. Preparethe samples for analysis as follows:

1. For 30-minute or 1-hour samples: Quan-titatively transfer the entire 10 mL amountof absorbing solution to a 25-mL volumetricflask and rinse with a small amount (<5 mL)of distilled water.

2. For 24-hour samples: If the volume of thesample is less than the original 50-mL vol-ume (permanent mark on the absorber), ad-just the volume back to the original volumewith distilled water to compensate for waterlost to evaporation during sampling. If thefinal volume is greater than the original vol-ume, the volume must be measured using agraduated cylinder. To analyze, pipet 10 mL


22


of the solution into a 25-mL volumetricflask.

11.2 Sample Analysis. For each set of deter-minations, prepare a reagent blank by add-ing 10 mL TCM absorbing solution to a 25-mL volumetric flask, and two control stand-ardscontainingapproximately 5and 15 µg SO2,

respectively. The control standards are pre-pared according to Section 10.2 or 10.3. Theanalysis is carried out as follows:

1. Allow the sample to stand 20 minutesafter the completion of sampling to allowany ozone to decompose (if applicable).

2. To each 25-mL volumetric flask con-taining reagent blank, sample, or controlstandard, add 1 mL of 0.6% sulfamic acid(Section 8.2.1) and allow to react for 10 min.

3. Accurately pipet 2 mL of 0.2% formalde-hyde solution (Section 8.2.2) and then 5 mLof pararosaniline solution (Section 8.2.13)into each flask. Start a laboratory timer setat 30 minutes.

4. Bring each flask to volume with recentlyboiled and cooled distilled water and mixthoroughly.

5. During the 30 minutes, the solutionsmust be in a temperature controlled environ-ment in the range of 20° to 30 °C maintainedto ± 1 °C. This temperature must also bewithin 1 °C of that used during calibration.

6. After 30 minutes and before 60 minutes,determine the corrected absorbances (equa-tion 10) of each solution at 548 nm using 1-cmoptical path length cells against a distilledwater reference (Section 10.1). (Distilled wateris used as a reference instead of the reagentblank because of the sensitivity of the reagentblank to temperature.)

7. Do not allow the colored solution tostand in the cells because a film may be de-posited. Clean the cells with isopropyl alco-hol after use.

8. The reagent blank must be within 0.03absorbance units of the intercept of the cali-bration equation determined in Section 10.

11.3 Absorbance range. If the absorbance ofthe sample solution ranges between 1.0 and2.0, the sample can be diluted 1:1 with a por-tion of the reagent blank and the absorbanceredetermined within 5 minutes. Solutionswith higher absorbances can be diluted up tosixfold with the reagent blank in order to ob-tain scale readings of less than 1.0 absorb-ance unit. However, it is recommended thata smaller portion (<10 mL) of the originalsample be reanalyzed (if possible) if the sam-ple requires a dilution greater than 1:1.

11.4 Reaqent disposal. All reagents con-taining mercury compounds must be storedand disposed of using one of the procedurescontained in Section 13. Until disposal, thediscarded solutions can be stored in closedglass containers and should be left in a fumehood.

12.0 Calculations.12.1 Calibration Slope, Intercept, and Correla-

tion Coefficient. The method of least squares

is used to calculate a calibration equation inthe form of:

y mx b= + ( )16where:y = corrected absorbance,m = slope, absorbance unit/µg SO2,

x = micrograms of SO2,

b = y intercept (absorbance units).

The slope (m), intercept (b), and correla-tion coefficient (r) are calculated as follows:

mn xy x y

n x x= ∑ − ∑ ∑

∑ − ∑( )( )

( )( )2 2 17

by m x

n=

∑ − ∑( )18

rm xy x y n

y y n=

∑ − ∑ ∑

∑ − ∑

( / )

( ) /( )

2 219

where n is the number of calibration points.A data form (Figure 5) is supplied for eas-

ily organizing calibration data when theslope, intercept, and correlation coefficientare calculated by hand.

12.2 Total Sample Volume. Determine thesampling volume at standard conditions asfollows:

VQ Q

tstdi f=+

×2

20( )

where:Vstd = sampling volume in std L,Qi = standard flow rate determined at the

initiation of sampling in std L/min,Qf = standard flow rate determined at the

completion of sampling is std L/min, andt = total sampling time, min.

12.3 Sulfur Dioxide Concentration. Calculateand report the concentration of each sampleas follows:

µg SO mA A B

V

V

V

o x

std

b

a

2

33

1021/

( )( )( )( )=

−×

where:A = corrected absorbance of the sample solu-

tion, from equation (10);Ao = corrected absorbance of the reagent

blank, using equation (10);Bx = calibration factor equal to Bs, Bg, or Bt

depending on the calibration procedureused, the reciprocal of the slope of the cali-bration equation;

Va = volume of absorber solution analyzed,mL;

Vb = total volume of solution in absorber (see11.1–2), mL; and

Vstd = standard air volume sampled, std L(from Section 12.2).


23


DATA FORM[For hand calculations]

Calibra-tion point

no.

Micro-grams So2

Absor-bance units

(x) (y) x2 xy y2

1 ........... .................. ................... .......... .......... ........2 ........... .................. ................... .......... .......... ........3 ........... .................. ................... .......... .......... ........4 ........... .................. ................... .......... .......... ........5 ........... .................. ................... .......... .......... ........6 ........... .................. ................... .......... .......... ........

Σ x=lll Σ y=lll Σ x2=lll ΣxylllΣy2llln=lll (number of pairs of coordinates.)llllllllllllllllllllllll

FIGURE 5. Data form for hand calculations.

12.4 Control Standards. Calculate the ana-lyzed micrograms of SO2 in each controlstandard as follows:

C A A Bq o x= −( ) × ( )22where:

Cq = analyzed µg SO2 in each control stand-ard,

A = corrected absorbance of the controlstandard, and

Ao = corrected absorbance of the reagentblank.

The difference between the true and ana-lyzed values of the control standards mustnot be greater than 1 µg. If the difference isgreater than 1 µg, the source of the discrep-ancy must be identified and corrected.

12.5 Conversion of µg/m3 to ppm (v/v). If de-sired, the concentration of sulfur dioxide atreference conditions can be converted to ppmSO2 (v/v) as follows:

ppm SOg SO

m

2

2

3

43 82 10 23= × ×

−µ. ( )

13.0 The TCM absorbing solution and anyreagents containing mercury compoundsmust be treated and disposed of by one of themethods discussed below. Both methods re-move greater than 99.99 percent of the mer-cury.

13.1 Disposal of Mercury-Containing Solu-tions.

13.2 Method for Forming an Amalgam.1. Place the waste solution in an uncapped

vessel in a hood.2. For each liter of waste solution, add ap-

proximately 10 g of sodium carbonate untilneutralization has occurred (NaOH may haveto be used).

3. Following neutralization, add 10 g ofgranular zinc or magnesium.

4. Stir the solution in a hood for 24 hours.Caution must be exercised as hydrogen gas isevolved by this treatment process.

5. After 24 hours, allow the solution tostand without stirring to allow the mercuryamalgam (solid black material) to settle tothe bottom of the waste receptacle.

6. Upon settling, decant and discard the su-pernatant liquid.

7. Quantitatively transfer the solid mate-rial to a container and allow to dry.

8. The solid material can be sent to a mer-cury reclaiming plant. It must not be dis-carded.

13.3 Method Using Aluminum Foil Strips.1. Place the waste solution in an uncapped

vessel in a hood.2. For each liter of waste solution, add ap-

proximately 10 g of aluminum foil strips. Ifall the aluminum is consumed and no gas isevolved, add an additional 10 g of foil. Repeatuntil the foil is no longer consumed andallow the gas to evolve for 24 hours.

3. Decant the supernatant liquid and dis-card.

4. Transfer the elemental mercury that hassettled to the bottom of the vessel to a stor-age container.

5. The mercury can be sent to a mercuryreclaiming plant. It must not be discarded.

14.0 References for SO2 Method.1. Quality Assurance Handbook for Air Pol-

lution Measurement Systems, Volume I,Principles. EPA–600/9–76–005, U.S. Environ-mental Protection Agency, Research Tri-angle Park, NC 27711, 1976.

2. Quality Assurance Handbook for Air Pol-lution Measurement Systems, Volume II,Ambient Air Specific Methods. EPA–600/4–77–027a, U.S. Environmental Protection Agency,Research Triangle Park, NC 27711, 1977.

3. Dasqupta, P. K., and K. B. DeCesare. Sta-bility of Sulfur Dioxide in Formaldehyde andIts Anomalous Behavior inTetrachloromercurate (II). Submitted forpublication in Atmospheric Environment, 1982.

4. West, P. W., and G. C. Gaeke. Fixation ofSulfur Dioxide as Disulfitomercurate (II) andSubsequent Colorimetric Estimation. Anal.Chem., 28:1816, 1956.

5. Ephraim, F. Inorganic Chemistry. P. C.L. Thorne and E. R. Roberts, Eds., 5th Edi-tion, Interscience, 1948, p. 562.

6. Lyles, G. R., F. B. Dowling, and V. J.Blanchard. Quantitative Determination ofFormaldehyde in the Parts Per Hundred Mil-lion Concentration Level. J. Air. Poll. Cont.Assoc., Vol. 15(106), 1965.

7. McKee, H. C., R. E. Childers, and O.Saenz, Jr. Collaborative Study of ReferenceMethod for Determination of Sulfur Dioxidein the Atmosphere (Pararosaniline Method).EPA–APTD–0903, U.S. Environmental Pro-tection Agency, Research Triangle Park, NC27711, September 1971.

8. Urone, P., J. B. Evans, and C. M. Noyes.Tracer Techniques in Sulfur—Air PollutionStudies Apparatus and Studies of Sulfur Di-oxide Colorimetric and ConductometricMethods. Anal. Chem., 37: 1104, 1965.


24

40 CFR Ch. I (7–1–01 Edition)Pt. 50, App. B

9. Bostrom, C. E. The Absorption of SulfurDioxide at Low Concentrations (pphm) Stud-ied by an Isotopic Tracer Method. Intern. J.Air Water Poll., 9:333, 1965.

10. Scaringelli, F. P., B. E. Saltzman, andS. A. Frey. Spectrophotometric Determina-tion of Atmospheric Sulfur Dioxide. Anal.Chem., 39: 1709, 1967.

11. Pate, J. B., B. E. Ammons, G. A. Swan-son, and J. P. Lodge, Jr. Nitrite Interferencein Spectrophotometric Determination of At-mospheric Sulfur Dioxide. Anal. Chem.,37:942, 1965.

12. Zurlo, N., and A. M. Griffini. Measure-ment of the Sulfur Dioxide Content of theAir in the Presence of Oxides of Nitrogen andHeavy Metals. Medicina Lavoro, 53:330, 1962.

13. Rehme, K. A., and F. P. Scaringelli. Ef-fect of Ammonia on the SpectrophotometricDetermination of Atmospheric Concentra-tions of Sulfur Dioxide. Anal. Chem., 47:2474,1975.

14. McCoy, R. A., D. E. Camann, and H. C.McKee. Collaborative Study of ReferenceMethod for Determination of Sulfur Dioxidein the Atmosphere (Pararosaniline Method)(24-Hour Sampling). EPA–650/4–74–027, U.S.Environmental Protection Agency, ResearchTriangle Park, NC 27711, December 1973.

15. Fuerst, R. G. Improved TemperatureStability of Sulfur Dioxide Samples Col-lected by the Federal Reference Method.EPA–600/4–78–018, U.S. Environmental Pro-tection Agency, Research Triangle Park, NC27711, April 1978.

16. Scaringelli, F. P., L. Elfers, D. Norris,and S. Hochheiser. Enhanced Stability ofSulfur Dioxide in Solution. Anal. Chem.,42:1818, 1970.

17. Martin, B. E. Sulfur Dioxide BubblerTemperature Study. EPA–600/4–77–040, U.S.Environmental Protection Agency, ResearchTriangle Park, NC 27711, August 1977.

18. American Society for Testing and Mate-rials. ASTM Standards, Water; AtmosphericAnalysis. Part 23. Philadelphia, PA, October1968, p. 226.

19. O’Keeffe, A. E., and G. C. Ortman. Pri-mary Standards for Trace Gas Analysis.Anal. Chem., 38:760, 1966.

20. Scaringelli, F. P., S. A. Frey, and B. E.Saltzman. Evaluation of Teflon PermeationTubes for Use with Sulfur Dioxide. Amer.Ind. Hygiene Assoc. J., 28:260, 1967.

21. Scaringelli, F. P., A. E. O’Keeffe, E.Rosenberg, and J. P. Bell, Preparation ofKnown Concentrations of Gases and VaporsWith Permeation Devices Calibrated Gravi-metrically. Anal. Chem., 42:871, 1970.

22. A Procedure for EstablishingTraceability of Gas Mixtures to Certain Na-tional Bureau of Standards Standard Ref-erence Materials. EPA–600/7–81–010, U.S. En-vironmental Protection Agency, Environ-mental Monitoring Systems Laboratory

(MD–77), Research Triangle Park, NC 27711,January 1981.

[47 FR 54899, Dec. 6, 1982; 48 FR 17355, Apr. 22,1983]

APPENDIX B TO PART 50—REFERENCEMETHOD FOR THE DETERMINATION OFSUSPENDED PARTICULATE MATTER INTHE ATMOSPHERE (HIGH-VOLUMEMETHOD)

1.0 Applicability.1.1 This method provides a measurement of

the mass concentration of total suspendedparticulate matter (TSP) in ambient air fordetermining compliance with the primaryand secondary national ambient air qualitystandards for particulate matter as specifiedin § 50.6 and § 50.7 of this chapter. The meas-urement process is nondestructive, and thesize of the sample collected is usually ade-quate for subsequent chemical analysis.Quality assurance procedures and guidanceare provided in part 58, appendixes A and B,of this chapter and in References 1 and 2.

2.0 Principle.2.1 An air sampler, properly located at the

measurement site, draws a measured quan-tity of ambient air into a covered housingand through a filter during a 24-hr (nominal)sampling period. The sampler flow rate andthe geometry of the shelter favor the collec-tion of particles up to 25–50 µm (aerodynamicdiameter), depending on wind speed and di-rection.(3) The filters used are specified tohave a minimum collection efficiency of 99percent for 0.3 µm (DOP) particles (see Sec-tion 7.1.4).

2.2 The filter is weighed (after moistureequilibration) before and after use to deter-mine the net weight (mass) gain. The totalvolume of air sampled, corrected to EPAstandard conditions (25 °C, 760 mm Hg [101kPa]), is determined from the measured flowrate and the sampling time. The concentra-tion of total suspended particulate matter inthe ambient air is computed as the mass ofcollected particles divided by the volume ofair sampled, corrected to standard condi-tions, and is expressed in micrograms perstandard cubic meter (µg/std m3). For sam-ples collected at temperatures and pressuressignificantly different than standard condi-tions, these corrected concentrations maydiffer substantially from actual concentra-tions (micrograms per actual cubic meter),particularly at high elevations. The actualparticulate matter concentration can be cal-culated from the corrected concentrationusing the actual temperature and pressureduring the sampling period.

3.0 Range.3.1 The approximate concentration range

of the method is 2 to 750 µg/std m3. The upperlimit is determined by the point at which thesampler can no longer maintain the specified


25

Environmental Protection Agency Pt. 50, App. B

*At elevated altitudes, the effectiveness ofautomatic flow controllers may be reducedbecause of a reduction in the maximum sam-pler flow.

flow rate due to the increased pressure dropof the loaded filter. This point is affected byparticle size distribution, moisture contentof the collected particles, and variabilityfrom filter to filter, among other things. Thelower limit is determined by the sensitivityof the balance (see Section 7.10) and by in-herent sources of error (see Section 6).

3.2 At wind speeds between 1.3 and 4.5 m/sec(3 and 10 mph), the high-volume air samplerhas been found to collect particles up to 25 to50 µm, depending on wind speed and direc-tion.(3) For the filter specified in Section 7.1,there is effectively no lower limit on the par-ticle size collected.

4.0 Precision.4.1 Based upon collaborative testing, the

relative standard deviation (coefficient ofvariation) for single analyst precision (re-peatability) of the method is 3.0 percent. Thecorresponding value for interlaboratory pre-cision (reproducibility) is 3.7 percent.(4)

5.0 Accuracy.5.1 The absolute accuracy of the method is

undefined because of the complex nature ofatmospheric particulate matter and the dif-ficulty in determining the ‘‘true’’ particulatematter concentration. This method providesa measure of particulate matter concentra-tion suitable for the purpose specified underSection 1.0, Applicability.

6.0 Inherent Sources of Error.6.1 Airflow variation. The weight of mate-

rial collected on the filter represents the (in-tegrated) sum of the product of the instanta-neous flow rate times the instantaneous par-ticle concentration. Therefore, dividing thisweight by the average flow rate over thesampling period yields the true particulatematter concentration only when the flowrate is constant over the period. The errorresulting from a nonconstant flow rate de-pends on the magnitude of the instantaneouschanges in the flow rate and in the particu-late matter concentration. Normally, sucherrors are not large, but they can be greatlyreduced by equipping the sampler with anautomatic flow controlling mechanism thatmaintains constant flow during the samplingperiod. Use of a contant flow controller isrecommended.*

6.2 Air volume measurement. If the flow ratechanges substantially or nonuniformly dur-ing the sampling period, appreciable error inthe estimated air volume may result fromusing the average of the presampling andpostsampling flow rates. Greater air volumemeasurement accuracy may be achieved by(1) equipping the sampler with a flow con-trolling mechanism that maintains constantair flow during the sampling period,* (2)

using a calibrated, continuous flow rate re-cording device to record the actual flow rateduring the samping period and integratingthe flow rate over the period, or (3) any othermeans that will accurately measure thetotal air volume sampled during the sam-pling period. Use of a continuous flow re-corder is recommended, particularly if thesampler is not equipped with a constant flowcontroller.

6.3 Loss of volatiles. Volatile particles col-lected on the filter may be lost during subse-quent sampling or during shipment and/orstorage of the filter prior to thepostsampling weighing.(5) Although suchlosses are largely unavoidable, the filtershould be reweighed as soon after samplingas practical.

6.4 Artifact particulate matter. Artifact par-ticulate matter can be formed on the surfaceof alkaline glass fiber filters by oxidation ofacid gases in the sample air, resulting in ahigher than true TSP determination.(6 7)This effect usually occurs early in the sam-ple period and is a function of the filter pHand the presence of acid gases. It is generallybelieved to account for only a small percent-age of the filter weight gain, but the effectmay become more significant where rel-atively small particulate weights are col-lected.

6.5 Humidity. Glass fiber filters are com-paratively insensitive to changes in relativehumidity, but collected particulate mattercan be hygroscopic.(8) The moisture condi-tioning procedure minimizes but may notcompletely eliminate error due to moisture.

6.6 Filter handling. Careful handling of thefilter between the presampling andpostsampling weighings is necessary to avoiderrors due to loss of fibers or particles fromthe filter. A filter paper cartridge or cassetteused to protect the filter can minimize han-dling errors. (See Reference 2, Section 2).

6.7 Nonsampled particulate matter. Particu-late matter may be deposited on the filter bywind during periods when the sampler is in-operative. (9) It is recommended that errorsfrom this source be minimized by an auto-matic mechanical device that keeps the fil-ter covered during nonsampling periods, orby timely installation and retrieval of filtersto minimize the nonsampling periods priorto and following operation.

6.8 Timing errors. Samplers are normallycontrolled by clock timers set to start andstop the sampler at midnight. Errors in thenominal 1,440-min sampling period may re-sult from a power interruption during thesampling period or from a discrepancy be-tween the start or stop time recorded on thefilter information record and the actualstart or stop time of the sampler. Such dis-crepancies may be caused by (1) poor resolu-tion of the timer set-points, (2) timer errordue to power interruption, (3) missetting of


26


(†) See note at beginning of Section 7 ofthis appendix.

‡ These specifications are in actual air vol-ume units; to convert to EPA standard airvolume units, multiply the specifications by(Pb/Pstd)(298/T) where Pb and T are the baro-metric pressure in mm Hg (or kPa) and thetemperature in K at the sampler, and Pstd is760 mm Hg (or 101 kPa).

the timer, or (4) timer malfunction. In gen-eral, digital electronic timers have muchbetter set-point resolution than mechanicaltimers, but require a battery backup systemto maintain continuity of operation after apower interruption. A continuous flow re-corder or elapsed time meter provides an in-dication of the sampler run-time, as well asindication of any power interruption duringthe sampling period and is therefore rec-ommended.

6.9 Recirculation of sampler exhaust. Understagnant wind conditions, sampler exhaustair can be resampled. This effect does not ap-pear to affect the TSP measurement sub-stantially, but may result in increased car-bon and copper in the collected sample. (10)This problem can be reduced by ducting theexhaust air well away, preferably downwind,from the sampler.

7.0 Apparatus.(See References 1 and 2 for quality assur-

ance information.)NOTE: Samplers purchased prior to the ef-

fective date of this amendment are not sub-ject to specifications preceded by (†).

7.1 Filter. (Filters supplied by the Environ-mental Protection Agency can be assumed tomeet the following criteria. Additional speci-fications are required if the sample is to beanalyzed chemically.)

7.1.1 Size: 20.3 ± 0.2 ×25.4 ± 0.2 cm (nominal8 ×10 in).

7.1.2 Nominal exposed area: 406.5 cm2 (63 in2).7.1.3. Material: Glass fiber or other rel-

atively inert, nonhygroscopic material. (8)7.1.4 Collection efficiency: 99 percent min-

imum as measured by the DOP test (ASTM–2986) for particles of 0.3 µm diameter.

7.1.5 Recommended pressure drop range: 42–54mm Hg (5.6–7.2 kPa) at a flow rate of 1.5 stdm3/min through the nominal exposed area.

7.1.6 pH: 6 to 10. (11)7.1.7 Integrity: 2.4 mg maximum weight

loss. (11)7.1.8 Pinholes: None.7.1.9 Tear strength: 500 g minimum for 20

mm wide strip cut from filter in weakest di-mension. (See ASTM Test D828–60).

7.1.10 Brittleness: No cracks or material sep-arations after single lengthwise crease.

7.2 Sampler. The air sampler shall providemeans for drawing the air sample, via re-duced pressure, through the filter at a uni-form face velocity.

7.2.1 The sampler shall have suitable meansto:

a. Hold and seal the filter to the samplerhousing.

b. Allow the filter to be changed conven-iently.

c. Preclude leaks that would cause error inthe measurement of the air volume passingthrough the filter.

d. (†) Manually adjust the flow rate to ac-commodate variations in filter pressure dropand site line voltage and altitude. The ad-justment may be accomplished by an auto-matic flow controller or by a manual flowadjustment device. Any manual adjustmentdevice must be designed with positivedetents or other means to avoid uninten-tional changes in the setting.

7.2.2 Minimum sample flow rate, heavily load-ed filter: 1.1 m3/min (39 ft3/min).‡

7.2.3 Maximum sample flow rate, clean filter:1.7 m3/min (60 ft3/min).‡

7.2.4 Blower Motor: The motor must be ca-pable of continuous operation for 24-hr peri-ods.

7.3 Sampler shelter.7.3.1 The sampler shelter shall:a. Maintain the filter in a horizontal posi-

tion at least 1 m above the sampler sup-porting surface so that sample air is drawndownward through the filter.

b. Be rectangular in shape with a gabledroof, similar to the design shown in Figure 1.

c. Cover and protect the filter and samplerfrom precipitation and other weather.

d. Discharge exhaust air at least 40 cmfrom the sample air inlet.

e. Be designed to minimize the collectionof dust from the supporting surface by incor-porating a baffle between the exhaust outletand the supporting surface.

7.3.2 The sampler cover or roof shall over-hang the sampler housing somewhat, asshown in Figure 1, and shall be mounted soas to form an air inlet gap between the coverand the sampler housing walls. † This sampleair inlet should be approximately uniform onall sides of the sampler. † The area of thesample air inlet must be sized to provide aneffective particle capture air velocity of be-tween 20 and 35 cm/sec at the recommendedoperational flow rate. The capture velocityis the sample air flow rate divided by theinlet area measured in a horizontal plane atthe lower edge of the cover. † Ideally, theinlet area and operational flow rate shouldbe selected to obtain a capture air velocityof 25 ±2 cm/sec.

7.4 Flow rate measurement devices.7.4.1 The sampler shall incorporate a flow

rate measurement device capable of indi-cating the total sampler flow rate. Two com-mon types of flow indicators covered in thecalibration procedure are (1) an electronicmass flowmeter and (2) an orifice or orifices


27


located in the sample air stream togetherwith a suitable pressure indicator such as amanometer, or aneroid pressure gauge. Apressure recorder may be used with an ori-fice to provide a continuous record of theflow. Other types of flow indicators (includ-ing rotameters) having comparable precisionand accuracy are also acceptable.

7.4.2 † The flow rate measurement devicemust be capable of being calibrated and readin units corresponding to a flow rate whichis readable to the nearest 0.02 std m3/minover the range 1.0 to 1.8 std m3/min.

7.5 Thermometer, to indicate the approxi-mate air temperature at the flow rate meas-urement orifice, when temperature correc-tions are used.

7.5.1 Range: ¥40° to +50 °C (223–323 K).7.5.2 Resolution: 2 °C (2 K).7.6 Barometer, to indicate barometric pres-

sure at the flow rate measurement orifice,when pressure corrections are used.

7.6.1 Range: 500 to 800 mm Hg (66–106 kPa).7.6.2 Resolution: ±5 mm Hg (0.67 kPa).7.7 Timing/control device.7.7.1 The timing device must be capable of

starting and stopping the sampler to obtainan elapsed run-time of 24 hr ±1 hr (1,440 ±60min).

7.7.2 Accuracy of time setting: ±30 min, orbetter. (See Section 6.8).

7.8 Flow rate transfer standard, traceable toa primary standard. (See Section 9.2.)

7.8.1 Approximate range: 1.0 to 1.8 m3/min.7.8.2 Resolution: 0.02 m3/min.7.8.3 Reproducibility: ±2 percent (2 times co-

efficient of variation) over normal ranges ofambient temperature and pressure for thestated flow rate range. (See Reference 2, Sec-tion 2.)

7.8.4 Maximum pressure drop at 1.7 std m3/min; 50 cm H2 O (5 kPa).

7.8.5 The flow rate transfer standard mustconnect without leaks to the inlet of thesampler and measure the flow rate of thetotal air sample.

7.8.6 The flow rate transfer standard mustinclude a means to vary the sampler flowrate over the range of 1.0 to 1.8 m3/min (35–64 ft3/min) by introducing various levels offlow resistance between the sampler and thetransfer standard inlet.

7.8.7 The conventional type of flow transferstandard consists of: An orifice unit withadapter that connects to the inlet of thesampler, a manometer or other device tomeasure orifice pressure drop, a means tovary the flow through the sampler unit, athermometer to measure the ambient tem-perature, and a barometer to measure ambi-ent pressure. Two such devices are shown inFigures 2a and 2b. Figure 2a shows multiplefixed resistance plates, which necessitatedisassembly of the unit each time the flowresistance is changed. A preferable design, il-lustrated in Figure 2b, has a variable flow re-striction that can be adjusted externally

without disassembly of the unit. Use of aconventional, orifice-type transfer standardis assumed in the calibration procedure (Sec-tion 9). However, the use of other types oftransfer standards meeting the above speci-fications, such as the one shown in Figure 2c,may be approved; see the note following Sec-tion 9.1.

7.9 Filter conditioning environment7.9.1 Controlled temperature: between 15° and

30 °C with less than ±3 °C variation duringequilibration period.

7.9.2 Controlled humidity: Less than 50 per-cent relative humidity, constant within ±5percent.

7.10 Analytical balance.7.10.1 Sensitivity: 0.1 mg.7.10.2 Weighing chamber designed to accept

an unfolded 20.3 x 25.4 cm (8 x 10 in) filter.7.11 Area light source, similar to X-ray film

viewer, to backlight filters for visual inspec-tion.

7.12 Numbering device, capable of printingidentification numbers on the filters beforethey are placed in the filter conditioning en-vironment, if not numbered by the supplier.

8.0 Procedure.(See References 1 and 2 for quality assur-

ance information.)8.1 Number each filter, if not already num-

bered, near its edge with a unique identifica-tion number.

8.2 Backlight each filter and inspect forpinholes, particles, and other imperfections;filters with visible imperfections must notbe used.

8.3 Equilibrate each filter in the condi-tioning environment for at least 24-hr.

8.4 Following equilibration, weigh each fil-ter to the nearest milligram and record thistare weight (Wi) with the filter identificationnumber.

8.5 Do not bend or fold the filter before col-lection of the sample.

8.6 Open the shelter and install a num-bered, preweighed filter in the sampler, fol-lowing the sampler manufacturer’s instruc-tions. During inclement weather, pre-cautions must be taken while changing fil-ters to prevent damage to the clean filterand loss of sample from or damage to the ex-posed filter. Filter cassettes that can beloaded and unloaded in the laboratory maybe used to minimize this problem (See Sec-tion 6.6).

8.7 Close the shelter and run the samplerfor at least 5 min to establish run-tempera-ture conditions.

8.8 Record the flow indicator reading and,if needed, the barometric pressure (P 3) andthe ambient temperature (T 3) see NOTE fol-lowing step 8.12). Stop the sampler. Deter-mine the sampler flow rate (see Section 10.1);if it is outside the acceptable range (1.1 to 1.7m3/min [39–60 ft3/min]), use a different filter,or adjust the sampler flow rate. Warning:Substantial flow adjustments may affect the


28


calibration of the orifice-type flow indica-tors and may necessitate recalibration.

8.9 Record the sampler identification infor-mation (filter number, site location or iden-tification number, sample date, and startingtime).

8.10 Set the timer to start and stop thesampler such that the sampler runs 24-hrs,from midnight to midnight (local time).

8.11 As soon as practical following the sam-pling period, run the sampler for at least 5min to again establish run-temperature con-ditions.

8.12 Record the flow indicator reading and,if needed, the barometric pressure (P 3) andthe ambient temperature (T 3).

NOTE: No onsite pressure or temperaturemeasurements are necessary if the samplerflow indicator does not require pressure ortemperature corrections (e.g., a mass flow-meter) or if average barometric pressure andseasonal average temperature for the site areincorporated into the sampler calibration(see step 9.3.9). For individual pressure andtemperature corrections, the ambient pres-sure and temperature can be obtained by on-site measurements or from a nearby weatherstation. Barometric pressure readings ob-tained from airports must be station pres-sure, not corrected to sea level, and mayneed to be corrected for differences in ele-vation between the sampler site and the air-port. For samplers having flow recorders butnot constant flow controllers, the averagetemperature and pressure at the site duringthe sampling period should be estimated fromweather bureau or other available data.

8.13 Stop the sampler and carefully removethe filter, following the sampler manufactur-er’s instructions. Touch only the outer edgesof the filter. See the precautions in step 8.6.

8.14 Fold the filter in half lengthwise sothat only surfaces with collected particulatematter are in contact and place it in the fil-ter holder (glassine envelope or manila fold-er).

8.15 Record the ending time or elapsed timeon the filter information record, either fromthe stop set-point time, from an elapsed timeindicator, or from a continuous flow record.The sample period must be 1,440 ± 60 min. fora valid sample.

8.16 Record on the filter information recordany other factors, such as meteorologicalconditions, construction activity, fires ordust storms, etc., that might be pertinent tothe measurement. If the sample is known tobe defective, void it at this time.

8.17 Equilibrate the exposed filter in theconditioning environment for at least 24-hrs.

8.18 Immediately after equilibration, re-weigh the filter to the nearest milligram andrecord the gross weight with the filter iden-tification number. See Section 10 for TSPconcentration calculations.

9.0 Calibration.

9.1 Calibration of the high volume sam-pler’s flow indicating or control device isnecessary to establish traceability of thefield measurement to a primary standard viaa flow rate transfer standard. Figure 3a illus-trates the certification of the flow ratetransfer standard and Figure 3b illustratesits use in calibrating a sampler flow indi-cator. Determination of the corrected flowrate from the sampler flow indicator, illus-trated in Figure 3c, is addressed in Section10.1

NOTE: The following calibration procedureapplies to a conventional orifice-type flowtransfer standard and an orifice-type flow in-dicator in the sampler (the most commontypes). For samplers using a pressure re-corder having a square-root scale, 3 other ac-ceptable calibration procedures are providedin Reference 12. Other types of transferstandards may be used if the manufactureror user provides an appropriately modifiedcalibration procedure that has been approvedby EPA under Section 2.8 of appendix C topart 58 of this chapter.

9.2 Certification of the flow rate transferstandard.

9.2.1 Equipment required: Positive displace-ment standard volume meter traceable tothe National Bureau of Standards (such as aRoots meter or equivalent), stop-watch, ma-nometer, thermometer, and barometer.

9.2.2 Connect the flow rate transfer stand-ard to the inlet of the standard volumemeter. Connect the manometer to measurethe pressure at the inlet of the standard vol-ume meter. Connect the orifice manometerto the pressure tap on the transfer standard.Connect a high-volume air pump (such as ahigh-volume sampler blower) to the outletside of the standard volume meter. See Fig-ure 3a.

9.2.3 Check for leaks by temporarily clamp-ing both manometer lines (to avoid fluidloss) and blocking the orifice with a large-di-ameter rubber stopper, wide cellophane tape,or other suitable means. Start the high-vol-ume air pump and note any change in thestandard volume meter reading. The readingshould remain constant. If the readingchanges, locate any leaks by listening for awhistling sound and/or retightening all con-nections, making sure that all gaskets areproperly installed.

9.2.4 After satisfactorily completing theleak check as described above, unclamp bothmanometer lines and zero both manometers.

9.2.5 Achieve the appropriate flow ratethrough the system, either by means of thevariable flow resistance in the transferstandard or by varying the voltage to the airpump. (Use of resistance plates as shown inFigure 1a is discouraged because the aboveleak check must be repeated each time a newresistance plate is installed.) At least fivedifferent but constant flow rates, evenly dis-tributed, with at least three in the specified


29


flow rate interval (1.1 to 1.7 m3/min [39–60 ft 3/min]), are required.

9.2.6 Measure and record the certificationdata on a form similar to the one illustratedin Figure 4 according to the following steps.

9.2.7 Observe the barometric pressure andrecord as P1 (item 8 in Figure 4).

9.2.8 Read the ambient temperature in thevicinity of the standard volume meter andrecord it as T1 (item 9 in Figure 4).

9.2.9 Start the blower motor, adjust theflow, and allow the system to run for at least1 min for a constant motor speed to be at-tained.

9.2.10 Observe the standard volume meterreading and simultaneously start a stop-watch. Record the initial meter reading (Vi)in column 1 of Figure 4.

9.2.11 Maintain this constant flow rateuntil at least 3 m3 of air have passed throughthe standard volume meter. Record thestandard volume meter inlet pressure ma-nometer reading as ∆P (column 5 in Figure4), and the orifice manometer reading as ∆H(column 7 in Figure 4). Be sure to indicatethe correct units of measurement.

9.2.12 After at least 3 m3 of air have passedthrough the system, observe the standardvolume meter reading while simultaneouslystopping the stopwatch. Record the finalmeter reading (Vf) in column 2 and theelapsed time (t) in column 3 of Figure 4.

9.2.13 Calculate the volume measured bythe standard volume meter at meter condi-tions of temperature and pressures asVm=Vf¥Vi. Record in column 4 of Figure 4.

9.2.14 Correct this volume to standard vol-ume (std m3) as follows:

V VP P

P

T

Tstd m

std

std=−1

1

∆

where:

Vstd = standard volume, std m3;Vm = actual volume measured by the stand-

ard volume meter;P1 = barometric pressure during calibration,

mm Hg or kPa;∆P = differential pressure at inlet to volume

meter, mm Hg or kPa;Pstd = 760 mm Hg or 101 kPa;Tstd = 298 K;T1 = ambient temperature during calibra-

tion, K.Calculate the standard flow rate (std m3/min)

as follows:

QV

tstd

std=

where:

Qstd = standard volumetric flow rate, std m3/min

t = elapsed time, minutes.

Record Qstd to the nearest 0.01 std m3/minin column 6 of Figure 4.

9.2.15 Repeat steps 9.2.9 through 9.2.14 forat least four additional constant flow rates,evenly spaced over the approximate range of1.0 to 1.8 std m3/min (35–64 ft3/min).

9.2.16 For each flow, compute√∆∆H (P1/Pstd)(298/T1)(column 7a of Figure 4) and plot these valueagainst Qstd as shown in Figure 3a. Be sure touse consistent units (mm Hg or kPa) for bar-ometric pressure. Draw the orifice transferstandard certification curve or calculate thelinear least squares slope (m) and intercept(b) of the certification curve:√∆∆H (P1/Pstd)(298/T1)=mQstd+b. See Figures 3 and 4. A certificationgraph should be readable to 0.02 std m3/min.

9.2.17 Recalibrate the transfer standard an-nually or as required by applicable qualitycontrol procedures. (See Reference 2.)

9.3 Calibration of sampler flow indicator.

NOTE: For samplers equipped with a flowcontrolling device, the flow controller mustbe disabled to allow flow changes duringcalibration of the sampler’s flow indicator,or the alternate calibration of the flow con-troller given in 9.4 may be used. For sam-plers using an orifice-type flow indicatordownstream of the motor, do not vary theflow rate by adjusting the voltage or powersupplied to the sampler.

9.3.1 A form similar to the one illustratedin Figure 5 should be used to record the cali-bration data.

9.3.2 Connect the transfer standard to theinlet of the sampler. Connect the orifice ma-nometer to the orifice pressure tap, as illus-trated in Figure 3b. Make sure there are noleaks between the orifice unit and the sam-pler.

9.3.3 Operate the sampler for at least 5minutes to establish thermal equilibriumprior to the calibration.

9.3.4 Measure and record the ambient tem-perature, T2, and the barometric pressure, P2,

during calibration.9.3.5 Adjust the variable resistance or, if

applicable, insert the appropriate resistanceplate (or no plate) to achieve the desiredflow rate.

9.3.6 Let the sampler run for at least 2 minto re-establish the run-temperature condi-tions. Read and record the pressure dropacross the orifice (∆H) and the sampler flowrate indication (I) in the appropriate col-umns of Figure 5.

9.3.7 Calculate √∆∆H(P2/Pstd)(298/T2) and de-termine the flow rate at standard conditions(Qstd) either graphically from the certifi-cation curve or by calculating Qstd from theleast square slope and intercept of the trans-fer standard’s transposed certification curve:Qstd=1/m √∆H(P2/Pstd)(298/T2)¥b. Record thevalue of Qstd on Figure 5.


30


9.3.8 Repeat steps 9.3.5, 9.3.6, and 9.3.7 forseveral additional flow rates distributed overa range that includes 1.1 to 1.7 std m3/min.

9.3.9 Determine the calibration curve byplotting values of the appropriate expressioninvolving I, selected from table 1, againstQstd. The choice of expression from table 1depends on the flow rate measurement de-vice used (see Section 7.4.1) and also onwhether the calibration curve is to incor-porate geographic average barometric pres-sure (Pa) and seasonal average temperature(Ta) for the site to approximate actual pres-sure and temperature. Where Pa and Ta canbe determined for a site for a seasonal periodsuch that the actual barometric pressure andtemperature at the site do not vary by morethan ±60 mm Hg (8 kPa) from Pa or ±15 °Cfrom Ta, respectively, then using Pa and Ta

avoids the need for subsequent pressure andtemperature calculation when the sampler isused. The geographic average barometricpressure (Pa) may be estimated from an alti-tude-pressure table or by making an (approx-imate) elevation correction of ¥26 mm Hg(¥3.46 kPa) for each 305 m (1,000 ft) above sealevel (760 mm Hg or 101 kPa). The seasonalaverage temperature (Ta) may be estimatedfrom weather station or other records. Besure to use consistent units (mm Hg or kPa)for barometric pressure.

9.3.10 Draw the sampler calibration curveor calculate the linear least squares slope(m), intercept (b), and correlation coefficientof the calibration curve: [Expression fromtable 1]= mQstd+b. See Figures 3 and 5. Cali-bration curves should be readable to 0.02 stdm3/min.

9.3.11 For a sampler equipped with a flowcontroller, the flow controlling mechanismshould be re-enabled and set to a flow nearthe lower flow limit to allow maximum con-trol range. The sample flow rate should beverified at this time with a clean filter in-stalled. Then add two or more filters to thesampler to see if the flow controller main-tains a constant flow; this is particularly im-portant at high altitudes where the range ofthe flow controller may be reduced.

9.4 Alternate calibration of flow-controlledsamplers. A flow-controlled sampler may becalibrated solely at its controlled flow rate,provided that previous operating history ofthe sampler demonstrates that the flow rateis stable and reliable. In this case, the flowindicator may remain uncalibrated butshould be used to indicate any relativechange between initial and final flows, andthe sampler should be recalibrated moreoften to minimize potential loss of samplesbecause of controller malfunction.

9.4.1 Set the flow controller for a flow nearthe lower limit of the flow range to allowmaximum control range.

9.4.2 Install a clean filter in the samplerand carry out steps 9.3.2, 9.3.3, 9.3.4, 9.3.6, and9.3.7.

9.4.3 Following calibration, add one or twoadditional clean filters to the sampler, re-connect the transfer standard, and operatethe sampler to verify that the controllermaintains the same calibrated flow rate; thisis particularly important at high altitudeswhere the flow control range may be re-duced.


31


10.0 Calculations of TSP Concentration.10.1 Determine the average sampler flow

rate during the sampling period according toeither 10.1.1 or 10.1.2 below.

10.1.1 For a sampler without a continuousflow recorder, determine the appropriate ex-pression to be used from table 2 cor-responding to the one from table 1 used instep 9.3.9. Using this appropriate expression,determine Qstd for the initial flow rate fromthe sampler calibration curve, either graphi-cally or from the transposed regression equa-tion:

Qstd =1/m ([Appropriate expression from table2]¥b)

Similarly, determine Qstd from the final flowreading, and calculate the average flow Qstd

as one-half the sum of the initial and finalflow rates.

10.1.2 For a sampler with a continuous flowrecorder, determine the average flow rate de-vice reading, I, for the period. Determine theappropriate expression from table 2 cor-responding to the one from table 1 used instep 9.3.9. Then using this expression and theaverage flow rate reading, determine Qstd

from the sampler calibration curve, eithergraphically or from the transposed regres-sion equation:

Qstd =

1/m ([Appropriate expression from table2]¥b)

If the trace shows substantial flow changeduring the sampling period, greater accuracy

may be achieved by dividing the samplingperiod into intervals and calculating an av-erage reading before determining Qstd.

10.2 Calculate the total air volume sampledas:

V¥Qstd×t

where:V = total air volume sampled, in standard

volume units, std m3/;Qstd = average standard flow rate, std m3/

min;t = sampling time, min.

10.3 Calculate and report the particulatematter concentration as:

TSPW W

V

f i=− ×( ) 10

6

where:TSP = mass concentration of total suspended

particulate matter, µg/std m3;Wi = initial weight of clean filter, g;Wf = final weight of exposed filter, g;V = air volume sampled, converted to stand-

ard conditions, std m3,106 = conversion of g to µg.

10.4 If desired, the actual particulate mat-ter concentration (see Section 2.2) can becalculated as follows:

(TSP)a=TSP (P3/Pstd)(298/T3)

where:(TSP)a = actual concentration at field condi-

tions, µg/m3;


32


TSP = concentration at standard conditions,µg/std m3;

P3 = average barometric pressure duringsampling period, mm Hg;

Pstd = 760 mn Hg (or 101 kPa);T3 = average ambient temperature during

sampling period, K.

11.0 References.1. Quality Assurance Handbook for Air Pol-

lution Measurement Systems, Volume I,Principles. EPA–600/9–76–005, U.S. Environ-mental Protection Agency, Research Tri-angle Park, NC 27711, 1976.

2. Quality Assurance Handbook for Air Pol-lution Measurement Systems, Volume II,Ambient Air Specific Methods. EPA–600/4–77–027a, U.S. Environmental Protection Agency,Research Triangle Park, NC 27711, 1977.

3. Wedding, J. B., A. R. McFarland, and J.E. Cernak. Large Particle Collection Charac-teristics of Ambient Aerosol Samplers. Envi-ron. Sci. Technol. 11:387–390, 1977.

4. McKee, H. C., et al. Collaborative Test-ing of Methods to Measure Air Pollutants, I.The High-Volume Method for Suspended Par-ticulate Matter. J. Air Poll. Cont. Assoc., 22(342), 1972.

5. Clement, R. E., and F. W. Karasek. Sam-ple Composition Changes in Sampling andAnalysis of Organic Compounds in Aerosols.The Intern. J. Environ. Anal. Chem., 7:109,1979.

6. Lee, R. E., Jr., and J. Wagman. A Sam-pling Anomaly in the Determination of At-mospheric Sulfuric Concentration. Am. Ind.Hygiene Assoc. J., 27:266, 1966.

7. Appel, B. R., et al. Interference Effectsin Sampling Particulate Nitrate in AmbientAir. Atmospheric Environment, 13:319, 1979.

8. Tierney, G. P., and W. D. Conner. Hygro-scopic Effects on Weight Determinations ofParticulates Collected on Glass-Fiber Fil-ters. Am. Ind. Hygiene Assoc. J., 28:363, 1967.

9. Chahal, H. S., and D. J. Romano. High-Volume Sampling Effect of Windborne Par-ticulate Matter Deposited During Idle Peri-ods. J. Air Poll. Cont. Assoc., Vol. 26 (885),1976.

10. Patterson, R. K. Aerosol Contaminationfrom High-Volume Sampler Exhaust. J. AirPoll. Cont. Assoc., Vol. 30 (169), 1980.

11. EPA Test Procedures for DeterminingpH and Integrity of High-Volume Air Filters.QAD/M–80.01. Available from the MethodsStandardization Branch, Quality AssuranceDivision, Environmental Monitoring Sys-tems Laboratory (MD–77), U.S. Environ-mental Protection Agency, Research Tri-angle Park, NC 27711, 1980.

12. Smith, F., P. S. Wohlschlegel, R. S. C.Rogers, and D. J. Mulligan. Investigation ofFlow Rate Calibration Procedures Associ-ated with the High-Volume Method for De-termination of Suspended Particulates.EPA–600/4–78–047, U.S. Environmental Pro-tection Agency, Research Triangle Park, NC,June 1978.


33



34



35



36

40 CFR Ch. I (7–1–01 Edition)Pt. 50, App. C

[47 FR 54912, Dec. 6, 1982; 48 FR 17355, Apr. 22, 1983]

APPENDIX C TO PART 50—MEASUREMENT

PRINCIPLE AND CALIBRATION PROCE-DURE FOR THE MEASUREMENT OF

CARBON MONOXIDE IN THE ATMOS-PHERE (NON-DISPERSIVE INFRARED

PHOTOMETRY)

MEASUREMENT PRINCIPLE

1. Measurements are based on the absorp-tion of infrared radiation by carbon mon-oxide (CO) in a non-dispersive photometer.Infrared energy from a source is passed

through a cell containing the gas sample tobe analyzed, and the quantitative absorptionof energy by CO in the sample cell is meas-ured by a suitable detector. The photometeris sensitized to CO by employing CO gas ineither the detector or in a filter cell in theoptical path, thereby limiting the measuredabsorption to one or more of the char-acteristic wavelengths at which CO stronglyabsorbs. Optical filters or other means may


37

Environmental Protection Agency Pt. 50, App. C

also be used to limit sensitivity of the pho-tometer to a narrow band of interest. Var-ious schemes may be used to provide a suit-able zero reference for the photometer. Themeasured absorption is converted to an elec-trical output signal, which is related to theconcentration of CO in the measurementcell.

2. An analyzer based on this principle willbe considered a reference method only if ithas been designated as a reference method inaccordance with part 53 of this chapter.

3. Sampling considerations.The use of a particle filter on the sample

inlet line of an NDIR CO analyzer is optionaland left to the discretion of the user or themanufacturer. Use of filter should depend onthe analyzer’s susceptibility to interference,malfunction, or damage due to particles.

CALIBRATION PROCEDURE

1. Principle. Either of two methods may beused for dynamic multipoint calibration ofCO analyzers:

(1) One method uses a single certifiedstandard cylinder of CO, diluted as necessarywith zero air, to obtain the various calibra-tion concentrations needed.

(2) The other method uses individual cer-tified standard cylinders of CO for each con-centration needed. Additional informationon calibration may be found in Section 2.0.9of Reference 1.

2. Apparatus. The major components andtypical configurations of the calibration sys-tems for the two calibration methods areshown in Figures 1 and 2.

2.1 Flow controller(s). Device capable ofadjusting and regulating flow rates. Flowrates for the dilution method (Figure 1) mustbe regulated to ± 1%.

2.2 Flow meter(s). Calibrated flow metercapable of measuring and monitoring flowrates. Flow rates for the dilution method(Figure 1) must be measured with an accu-racy of ± 2% of the measured value.

2.3 Pressure regulator(s) for standard COcylinder(s). Regulator must have nonreac-tive diaphragm and internal parts and a suit-able delivery pressure.

2.4 Mixing chamber. A chamber designed toprovide thorough mixing of CO and diluentair for the dilution method.

2.5 Output manifold. The output manifoldshould be of sufficient diameter to insure aninsignificant pressure drop at the analyzerconnection. The system must have a vent de-signed to insure atmospheric pressure at themanifold and to prevent ambient air fromentering the manifold.

3. Reagents.3.1 CO concentration standard(s). Cyl-

inder(s) of CO in air containing appropriateconcentrations(s) of CO suitable for the se-lected operating range of the analyzer undercalibration; CO standards for the dilutionmethod may be contained in a nitrogen ma-

trix if the zero air dilution ratio is not lessthan 100:1. The assay of the cylinder(s) mustbe traceable either to a National Bureau ofStandards (NBS) CO in air Standard Ref-erence Material (SRM) or to an NBS/EPA-ap-proved commercially available Certified Ref-erence Material (CRM). CRM’s are describedin Reference 2, and a list of CRM sources isavailable from the address shown for Ref-erence 2. A recommended protocol for certi-fying CO gas cylinders against either a COSRM or a CRM is given in Reference 1. COgas cylinders should be recertified on a reg-ular basis as determined by the local qualitycontrol program.

3.2 Dilution gas (zero air). Air, free of con-taminants which will cause a detectable re-sponse on the CO analyzer. The zero airshould contain <0.1 ppm CO. A procedure forgenerating zero air is given in Reference 1.

4. Procedure Using Dynamic Dilution Method.4.1 Assemble a dynamic calibration system

such as the one shown in Figure 1. All cali-bration gases including zero air must be in-troduced into the sample inlet of the ana-lyzer system. For specific operating instruc-tions refer to the manufacturer’s manual.

4.2 Insure that all flowmeters are properlycalibrated, under the conditions of use, if ap-propriate, against an authoritative standardsuch as a soap-bubble meter or wet-testmeter. All volumetric flowrates should becorrected to 25 °C and 760 mm Hg (101 kPa).A discussion on calibration of flowmeters isgiven in Reference 1.

4.3 Select the operating range of the CO an-alyzer to be calibrated.

4.4 Connect the signal output of the CO an-alyzer to the input of the strip chart re-corder or other data collection device. Alladjustments to the analyzer should be basedon the appropriate strip chart or data devicereadings. References to analyzer responses inthe procedure given below refer to recorderor data device responses.

4.5 Adjust the calibration system to deliverzero air to the output manifold. The total airflow must exceed the total demand of the an-alyzer(s) connected to the output manifoldto insure that no ambient air is pulled intothe manifold vent. Allow the analyzer tosample zero air until a stable respose is ob-tained. After the response has stabilized, ad-just the analyzer zero control. Offsetting theanalyzer zero adjustments to +5 percent ofscale is recommended to facilitate observingnegative zero drift. Record the stable zeroair response as ZCO.

4.6 Adjust the zero air flow and the CO flowfrom the standard CO cylinder to provide adiluted CO concentration of approximately80 percent of the upper range limit (URL) ofthe operating range of the analyzer. Thetotal air flow must exceed the total demandof the analyzer(s) connected to the outputmanifold to insure that no ambient air is


38


pulled into the manifold vent. The exact COconcentration is calculated from:

[ ][ ]

( )COCO F

F FOUT

STD CO

D CO

=×

+1

where:[CO]OUT = diluted CO concentration at the

output manifold, ppm;[CO]STD = concentration of the undiluted CO

standard, ppm;FCO = flow rate of the CO standard corrected

to 25 °C and 760 mm Hg, (101 kPa), L/min;and

FD = flow rate of the dilution air correctedto 25 °C and 760 mm Hg, (101 kPa), L/min.

Sample this CO concentration until a sta-ble response is obtained. Adjust the analyzerspan control to obtain a recorder response asindicated below:Recorder response (percent scale) =

[ ]( )

CO

URLZOUT

CO× +100 2

where:URL = nominal upper range limit of the ana-

lyzer’s operating range, andZCO = analyzer response to zero air, % scale.

If substantial adjustment of the analyzerspan control is required, it may be necessaryto recheck the zero and span adjustments byrepeating Steps 4.5 and 4.6. Record the COconcentration and the analyzer’s response.4.7 Generate several additional concentra-tions (at least three evenly spaced pointsacross the remaining scale are suggested to

verify linearity) by decreasing FCO or in-creasing FD. Be sure the total flow exceedsthe analyzer’s total flow demand. For eachconcentration generated, calculate the exactCO concentration using Equation (1). Recordthe concentration and the analyzer’s re-sponse for each concentration. Plot the ana-lyzer responses versus the corresponding COconcentrations and draw or calculate thecalibration curve.

5. Procedure Using Multiple Cylinder Method.Use the procedure for the dynamic dilutionmethod with the following changes:

5.1 Use a multi-cylinder system such as thetypical one shown in Figure 2.

5.2 The flowmeter need not be accuratelycalibrated, provided the flow in the outputmanifold exceeds the analyzer’s flow de-mand.

5.3 The various CO calibration concentra-tions required in Steps 4.6 and 4.7 are ob-tained without dilution by selecting the ap-propriate certified standard cylinder.

REFERENCES

1. Quality Assurance Handbook for Air Pol-lution Measurement Systems, Volume II—Ambient Air Specific Methods, EPA–600/4–77–027a, U.S. Environmental Protection Agency,Environmental Monitoring Systems Labora-tory, Research Triangle Park, NC 27711, 1977.

2. A procedure for EstablishingTraceability of Gas Mixtures to Certain Na-tional Bureau of Standards Standard Ref-erence Materials. EPA–600/7–81–010, U.S. En-vironmental Protection Agency, Environ-mental Monitoring Systems Laboratory(MD–77), Research Triangle Park, NC 27711,January 1981.


39

Environmental Protection Agency Pt. 50, App. C


40


[47 FR 54922, Dec. 6, 1982; 48 FR 17355, Apr. 22, 1983]


41

Environmental Protection Agency Pt. 50, App. D

APPENDIX D TO PART 50—MEASUREMENT

PRINCIPLE AND CALIBRATION PROCE-DURE FOR THE MEASUREMENT OF

OZONE IN THE ATMOSPHERE

MEASUREMENT PRINCIPLE

1. Ambient air and ethylene are deliveredsimultaneously to a mixing zone where theozone in the air reacts with the ethylene toemit light, which is detected by aphotomultiplier tube. The resultingphotocurrent is amplified and is either readdirectly or displayed on a recorder.

2. An analyzer based on this principle willbe considered a reference method only if ithas been designated as a reference method inaccordance with part 53 of this chapter andcalibrated as follows:

CALIBRATION PROCEDURE

1. Principle. The calibration procedure isbased on the photometric assay of ozone (O3)concentrations in a dynamic flow system.The concentration of O3 in an absorption cellis determined from a measurement of theamount of 254 nm light absorbed by the sam-ple. This determination requires knowledgeof (1) the absorption coefficient (α) of O3 at254 nm, (2) the optical path length (l)through the sample, (3) the transmittance ofthe sample at a wavelength of 254 nm, and (4)the temperature (T) and pressure (P) of thesample. The transmittance is defined as theratio I/I0, where I is the intensity of lightwhich passes through the cell and is sensedby the detector when the cell contains an O3

sample, and I0 is the intensity of light whichpasses through the cell and is sensed by thedetector when the cell contains zero air. It isassumed that all conditions of the system,except for the contents of the absorptioncell, are identical during measurement of Iand I0. The quantities defined above are re-lated by the Beer-Lambert absorption law,

Transmit ceI

Ie

O

actan ( )= =

− l1

where:

α = absorption coefficient of O3 at 254nm=308±4 atm¥1 cm¥1 at 0 °C and 760torr. (1, 2, 3, 4, 5, 6, 7)

c = O3 concentration in atmospheresl = optical path length in cm

In practice, a stable O3 generator is used toproduce O3 concentrations over the requiredrange. Each O3 concentration is determinedfrom the measurement of the transmittance(I/I0) of the sample at 254 nm with a photom-eter of path length l and calculated from theequation,

c atm n I I a

or

c ppm n I I b

O

O

( ) ( / ) ( )

( ) ( / ) ( )

= −

= −

11 2

101 2

6

α

α

l

lThe calculated O3 concentrations must becorrected for O3 losses which may occur inthe photometer and for the temperature andpressure of the sample.

2. Applicability. This procedure is applicableto the calibration of ambient air O3 ana-lyzers, either directly or by means of atransfer standard certified by this procedure.Transfer standards must meet the require-ments and specifications set forth in Ref-erence 8.

3. Apparatus. A complete UV calibrationsystem consists of an ozone generator, anoutput port or manifold, a photometer, anappropriate source of zero air, and othercomponents as necessary. The configurationmust provide a stable ozone concentration atthe system output and allow the photometerto accurately assay the output concentra-tion to the precision specified for the pho-tometer (3.1). Figure 1 shows a commonlyused configuration and serves to illustratethe calibration procedure which follows.Other configurations may require appro-priate variations in the procedural steps. Allconnections between components in the cali-bration system downstream of the O3 gener-ator should be of glass, Teflon, or other rel-atively inert materials. Additional informa-tion regarding the assembly of a UV photo-metric calibration apparatus is given in Ref-erence 9. For certification of transfer stand-ards which provide their own source of O3,

the transfer standard may replace the O3

generator and possibly other componentsshown in Figure 1; see Reference 8 for guid-ance.

3.1 UV photometer. The photometer consistsof a low-pressure mercury discharge lamp,(optional) collimation optics, an absorptioncell, a detector, and signal-processing elec-tronics, as illustrated in Figure 1. It must becapable of measuring the transmittance, I/I0,

at a wavelength of 254 nm with sufficientprecision such that the standard deviation ofthe concentration measurements does notexceed the greater of 0.005 ppm or 3% of theconcentration. Because the low-pressuremercury lamp radiates at several wave-lengths, the photometer must incorporatesuitable means to assure that no O3 is gen-erated in the cell by the lamp, and that atleast 99.5% of the radiation sensed by the de-tector is 254 nm radiation. (This can be read-ily achieved by prudent selection of opticalfilter and detector response characteristics.)The length of the light path through the ab-sorption cell must be known with an accu-racy of at least 99.5%. In addition, the celland associated plumbing must be designed to


42

40 CFR Ch. I (7–1–01 Edition)Pt. 50, App. D

minimize loss of O3 from contact with cellwalls and gas handling components. See Ref-erence 9 for additional information.

3.2 Air flow controllers. Devices capable ofregulating air flows as necessary to meet theoutput stability and photometer precisionrequirements.

3.3 Ozone generator. Device capable of gen-erating stable levels of O3 over the requiredconcentration range.

3.4 Output manifold. The output manifoldshould be constructed of glass, Teflon, orother relatively inert material, and shouldbe of sufficient diameter to insure a neg-ligible pressure drop at the photometer con-nection and other output ports. The systemmust have a vent designed to insure atmos-pheric pressure in the manifold and to pre-vent ambient air from entering the manifold.

3.5 Two-way valve. Manual or automaticvalve, or other means to switch the photom-eter flow between zero air and the O3 con-centration.

3.6 Temperature indicator. Accurate to ±1 °C.3.7 Barometer or pressure indicator. Accurate

to ±2 torr.4. Reagents.4.1 Zero air. The zero air must be free of

contaminants which would cause a detect-able response from the O3 analyzer, and itshould be free of NO, C2 H4, and other specieswhich react with O3. A procedure for gener-ating suitable zero air is given in Reference9. As shown in Figure 1, the zero air suppliedto the photometer cell for the I0 referencemeasurement must be derived from the samesource as the zero air used for generation ofthe ozone concentration to be assayed (Imeasurement). When using the photometerto certify a transfer standard having its ownsource of ozone, see Reference 8 for guidanceon meeting this requirement.

5. Procedure.5.1 General operation. The calibration pho-

tometer must be dedicated exclusively to useas a calibration standard. It should alwaysbe used with clean, filtered calibration gases,and never used for ambient air sampling.Consideration should be given to locatingthe calibration photometer in a clean labora-tory where it can be stationary, protectedfrom physical shock, operated by a respon-sible analyst, and used as a common stand-ard for all field calibrations via transferstandards.

5.2 Preparation. Proper operation of thephotometer is of critical importance to theaccuracy of this procedure. The followingsteps will help to verify proper operation.The steps are not necessarily required priorto each use of the photometer. Upon initialoperation of the photometer, these stepsshould be carried out frequently, with allquantitative results or indications recordedin a chronological record either in tabularform or plotted on a graphical chart. As theperformance and stability record of the pho-

tometer is established, the frequency ofthese steps may be reduced consistent withthe documented stability of the photometer.

5.2.1 Instruction manual: Carry out all setup and adjustment procedures or checks asdescribed in the operation or instructionmanual associated with the photometer.

5.2.2 System check: Check the photometersystem for integrity, leaks, cleanliness,proper flowrates, etc. Service or replace fil-ters and zero air scrubbers or otherconsumable materials, as necessary.

5.2.3 Linearity: Verify that the photometermanufacturer has adequately establishedthat the linearity error of the photometer isless than 3%, or test the linearity by dilu-tion as follows: Generate and assay an O3

concentration near the upper range limit ofthe system (0.5 or 1.0 ppm), then accuratelydilute that concentration with zero air andreassay it. Repeat at several different dilu-tion ratios. Compare the assay of the origi-nal concentration with the assay of the di-luted concentration divided by the dilutionratio, as follows

EA A R

A=

−×1 2

1

100% 3/

( )

where:E = linearity error, percentA1 = assay of the original concentrationA2 = assay of the diluted concentrationR = dilution ratio = flow of original con-

centration divided by the total flow

The linearity error must be less than 5%.Since the accuracy of the measured flow-rates will affect the linearity error as meas-ured this way, the test is not necessarilyconclusive. Additional information onverifying linearity is contained in Reference9.

5.2.4 Intercomparison: When possible, thephotometer should be occasionally intercom-pared, either directly or via transfer stand-ards, with calibration photometers used byother agencies or laboratories.

5.2.5 Ozone losses: Some portion of the O3

may be lost upon contact with the photom-eter cell walls and gas handling components.The magnitude of this loss must be deter-mined and used to correct the calculated O3

concentration. This loss must not exceed 5%.Some guidelines for quantitatively deter-mining this loss are discussed in Reference 9.

5.3 Assay of O3 concentrations.5.3.1 Allow the photometer system to warm

up and stabilizer.5.3.2 Verify that the flowrate through the

photometer absorption cell, F allows the cellto be flushed in a reasonably short period oftime (2 liter/min is a typical flow). The preci-sion of the measurements is inversely re-lated to the time required for flushing, sincethe photometer drift error increases withtime.


43


5.3.3 Insure that the flowrate into the out-put manifold is at least 1 liter/min greaterthan the total flowrate required by the pho-tometer and any other flow demand con-nected to the manifold.

5.3.4 Insure that the flowrate of zero air,Fz, is at least 1 liter/min greater than theflowrate required by the photometer.

5.3.5 With zero air flowing in the outputmanifold, actuate the two-way valve to allowthe photometer to sample first the manifoldzero air, then Fz. The two photometer read-ings must be equal (I=Io).

NOTE: In some commercially availablephotometers, the operation of the two-wayvalve and various other operations in section5.3 may be carried out automatically by thephotometer.

5.3.6 Adjust the O3 generator to produce anO3 concentration as needed.

5.3.7 Actuate the two-way valve to allowthe photometer to sample zero air until theabsorption cell is thoroughly flushed andrecord the stable measured value of Io.

5.3.8 Actuate the two-way valve to allowthe photometer to sample the ozone con-centration until the absorption cell is thor-oughly flushed and record the stable meas-ured value of I.

5.3.9 Record the temperature and pressureof the sample in the photometer absorptioncell. (See Reference 9 for guidance.)

5.3.10 Calculate the O3 concentration fromequation 4. An average of several determina-tions will provide better precision.

[ ] ln)

( )Oa

I

I

T

P LOUTO

3

61

273

760 104= −

×

l

where:[O3]OUT = O3 concentration, ppmα = absorption coefficient of O3 at 254 nm=308

atm¥1 cm¥1 at 0 °C and 760 torrl = optical path length, cmT = sample temperature, KP = sample pressure, torrL = correction factor for O3 losses from

5.2.5=(1-fraction O3 lost).

NOTE: Some commercial photometers mayautomatically evaluate all or part of equa-tion 4. It is the operator’s responsibility toverify that all of the information requiredfor equation 4 is obtained, either automati-cally by the photometer or manually. For‘‘automatic’’ photometers which evaluatethe first term of equation 4 based on a linearapproximation, a manual correction may berequired, particularly at higher O3 levels.See the photometer instruction manual andReference 9 for guidance.

5.3.11 Obtain additional O3 concentrationstandards as necessary by repeating steps5.3.6 to 5.3.10 or by Option 1.

5.4 Certification of transfer standards. Atransfer standard is certified by relating theoutput of the transfer standard to one or

more ozone standards as determined accord-ing to section 5.3. The exact procedure variesdepending on the nature and design of thetransfer standard. Consult Reference 8 forguidance.

5.5 Calibration of ozone analyzers. Ozoneanalyzers are calibrated as follows, usingozone standards obtained directly accordingto section 5.3 or by means of a certifiedtransfer standard.

5.5.1 Allow sufficient time for the O3 ana-lyzer and the photometer or transfer stand-ard to warmup and stabilize.

5.5.2 Allow the O3 analyzer to sample zeroair until a stable response is obtained andadjust the O3 analyzer’s zero control. Offset-ting the analyzer’s zero adjustment to +5%of scale is recommended to facilitate observ-ing negative zero drift. Record the stablezero air response as ‘‘Z’’.

5.5.3 Generate an O3 concentration stand-ard of approximately 80% of the desiredupper range limit (URL) of the O3 analyzer.Allow the O3 analyzer to sample this O3 con-centration standard until a stable responseis obtained.

5.5.4 Adjust the O3 analyzer’s span controlto obtain a convenient recorder response asindicated below:

recorder response (%scale)=

[ ]( )

O

URLZOUT3 100 5×

+

where:

URL = upper range limit of the O3 analyzer,ppm

Z = recorder response with zero air, % scale

Record the O3 concentration and the cor-responding analyzer response. If substantialadjustment of the span control is necessary,recheck the zero and span adjustments by re-peating steps 5.5.2 to 5.5.4.

5.5.5 Generate several other O3 concentra-tion standards (at least 5 others are rec-ommended) over the scale range of the O3 an-alyzer by adjusting the O3 source or by Op-tion 1. For each O3 concentration standard,record the O3 and the corresponding analyzerresponse.

5.5.6 Plot the O3 analyzer responses versusthe corresponding O3 concentrations anddraw the O3 analyzer’s calibration curve orcalculate the appropriate response factor.

5.5.7 Option 1: The various O3 concentra-tions required in steps 5.3.11 and 5.5.5 may beobtained by dilution of the O3 concentrationgenerated in steps 5.3.6 and 5.5.3. With thisoption, accurate flow measurements are re-quired. The dynamic calibration system maybe modified as shown in Figure 2 to allow fordilution air to be metered in downstream ofthe O3 generator. A mixing chamber betweenthe O3 generator and the output manifold isalso required. The flowrate through the O3

generator (Fo) and the dilution air flowrate


44

40 CFR Ch. I (7–1–01 Edition)Pt. 50, App. D

(FD) are measured with a reliable flow or vol-ume standard traceable to NBS. Each O3 con-centration generated by dilution is cal-culated from:

[ ] [ ] ( )O OF

F FOUT OUT

O

O D

3 3 6′ =+

where:

[O3]′OUT = diluted O3 concentration, ppmF0 = flowrate through the O3 generator, liter/

minFD = diluent air flowrate, liter/min

REFERENCES

1. E.C.Y. Inn and Y. Tanaka, ‘‘Absorptioncoefficient of Ozone in the Ultraviolet andVisible Regions’’, J. Opt. Soc. Am., 43, 870(1953).

2. A. G. Hearn, ‘‘Absorption of Ozone in theUltraviolet and Visible Regions of the Spec-trum’’, Proc. Phys. Soc. (London), 78, 932(1961).

3. W. B. DeMore and O. Raper, ‘‘HartleyBand Extinction Coefficients of Ozone in theGas Phase and in Liquid Nitrogen, Carbon

Monoxide, and Argon’’, J. Phys. Chem., 68, 412(1964).

4. M. Griggs, ‘‘Absorption Coefficients ofOzone in the Ultraviolet and Visible Re-gions’’, J. Chem. Phys., 49, 857 (1968).

5. K. H. Becker, U. Schurath, and H. Seitz,‘‘Ozone Olefin Reactions in the Gas Phase. 1.Rate Constants and Activation Energies’’,Int’l Jour. of Chem. Kinetics, VI, 725 (1974).

6. M. A. A. Clyne and J. A. Coxom, ‘‘Ki-netic Studies of Oxy-halogen Radical Sys-tems’’, Proc. Roy. Soc., A303, 207 (1968).

7. J. W. Simons, R. J. Paur, H. A. Webster,and E. J. Bair, ‘‘Ozone Ultraviolet Pho-tolysis. VI. The Ultraviolet Spectrum’’, J.Chem. Phys., 59, 1203 (1973).

8. Transfer Standards for Calibration ofAmbient Air Monitoring Analyzers forOzone, EPA publication number EPA–600/4–79–056, EPA, National Exposure ResearchLaboratory, Department E, (MD–77B), Re-search Triangle Park, NC 27711.

9. Technical Assistance Document for theCalibration of Ambient Ozone Monitors, EPApublication number EPA–600/4–79–057, EPA,National Exposure Research Laboratory, De-partment E, (MD–77B), Research TrianglePark, NC 27711.


45



46

40 CFR Ch. I (7–1–01 Edition)Pt. 50, App. F

[44 FR 8224, Feb. 8, 1979, as amended at 62 FR38895, July 18, 1997]

APPENDIX E TO PART 50 [RESERVED]

APPENDIX F TO PART 50—MEASUREMENTPRINCIPLE AND CALIBRATION PROCE-DURE FOR THE MEASUREMENT OF NI-TROGEN DIOXIDE IN THE ATMOSPHERE(GAS PHASE CHEMILUMINESCENCE)

PRINCIPLE AND APPLICABILITY

1. Atmospheric concentrations of nitrogendioxide (NO2) are measured indirectly byphotometrically measuring the light inten-sity, at wavelengths greater than 600nanometers, resulting from the chemilumi-nescent reaction of nitric oxide (NO) withozone (O3). (1,2,3) NO2 is first quantitativelyreduced to NO(4,5,6) by means of a converter.NO, which commonly exists in ambient airtogether with NO2, passes through the con-verter unchanged causing a resultant totalNOX concentration equal to NO+NO2. A sam-ple of the input air is also measured withouthaving passed through the converted. Thislatter NO measurement is subtracted fromthe former measurement (NO+NO2) to yieldthe final NO2 measurement. The NO andNO+NO2 measurements may be made concur-rently with dual systems, or cyclically withthe same system provided the cycle timedoes not exceed 1 minute.

2. Sampling considerations.2.1 Chemiluminescence NO/NOX/NO2 ana-

lyzers will respond to other nitrogen con-taining compounds, such as peroxyacetyl ni-trate (PAN), which might be reduced to NOin the thermal converter. (7) Atmosphericconcentrations of these potential inter-ferences are generally low relative to NO2

and valid NO2 measurements may be ob-tained. In certain geographical areas, wherethe concentration of these potential inter-ferences is known or suspected to be highrelative to NO2, the use of an equivalentmethod for the measurement of NO2 is rec-ommended.

2.2 The use of integrating flasks on thesample inlet line of chemiluminescence NO/NOX/NO2 analyzers is optional and left tocouraged. The sample residence time be-tween the sampling point and the analyzershould be kept to a minimum to avoid erro-neous NO2 measurements resulting from thereaction of ambient levels of NO and O3 inthe sampling system.

2.3 The use of particulate filters on thesample inlet line of chemiluminescence NO/NOX/NO2 analyzers is optional and left to thediscretion of the user or the manufacturer.Use of the filter should depend on the ana-lyzer’s susceptibility to interference, mal-function, or damage due to particulates.Users are cautioned that particulate matterconcentrated on a filter may cause erroneous

NO2 measurements and therefore filtersshould be changed frequently.

3. An analyzer based on this principle willbe considered a reference method only if ithas been designated as a reference method inaccordance with part 53 of this chapter.

CALIBRATION

1. Alternative A—Gas phase titration (GPT)of an NO standard with O3.

Major equipment required: Stable O3 gener-ator. Chemiluminescence NO/NOX/NO2 ana-lyzer with strip chart recorder(s). NO con-centration standard.

1.1 Principle. This calibration technique isbased upon the rapid gas phase reaction be-tween NO and O3 to produce stoichiometricquantities of NO2 in accordance with the fol-lowing equation: (8)

NO O NO O+ → +3 2 2 1( )The quantitative nature of this reaction issuch that when the NO concentration isknown, the concentration of NO2 can be de-termined. Ozone is added to excess NO in adynamic calibration system, and the NOchannel of the chemiluminescence NO/NOX/NO2 analyzer is used as an indicator ofchanges in NO concentration. Upon the addi-tion of O3, the decrease in NO concentrationobserved on the calibrated NO channel isequivalent to the concentration of NO2 pro-duced. The amount of NO2 generated may bevaried by adding variable amounts of O3 froma stable uncalibrated O3 generator. (9)

1.2 Apparatus. Figure 1, a schematic of atypical GPT apparatus, shows the suggestedconfiguration of the components listedbelow. All connections between componentsin the calibration system downstream fromthe O3 generator should be of glass, Teflon ,

or other non-reactive material.1.2.1 Air flow controllers. Devices capable of

maintaining constant air flows within ±2% ofthe required flowrate.

1.2.2 NO flow controller. A device capable ofmaintaining constant NO flows within ±2%of the required flowrate. Component parts incontact with the NO should be of a non-reac-tive material.

1.2.3 Air flowmeters. Calibrated flowmeterscapable of measuring and monitoring airflowrates with an accuracy of ±2% of themeasured flowrate.

1.2.4 NO flowmeter. A calibrated flowmetercapable of measuring and monitoring NOflowrates with an accuracy of ±2% of themeasured flowrate. (Rotameters have beenreported to operate unreliably when meas-uring low NO flows and are not rec-ommended.)

1.2.5 Pressure regulator for standard NO cyl-inder. This regulator must have a nonreac-tive diaphragm and internal parts and a suit-able delivery pressure.


47

Environmental Protection Agency Pt. 50, App. F

1.2.6 Ozone generator. The generator mustbe capable of generating sufficient and stablelevels of O3 for reaction with NO to generateNO2 concentrations in the range required.Ozone generators of the electric dischargetype may produce NO and NO2 and are notrecommended.

1.2.7 Valve. A valve may be used as shownin Figure 1 to divert the NO flow when zeroair is required at the manifold. The valveshould be constructed of glass, Teflon , orother nonreactive material.

1.2.8 Reaction chamber. A chamber, con-structed of glass, Teflon , or other nonreac-tive material, for the quantitative reactionof O3 with excess NO. The chamber should beof sufficient volume (VRC) such that the resi-dence time (tR) meets the requirements spec-ified in 1.4. For practical reasons, tR shouldbe less than 2 minutes.

1.2.9 Mixing chamber. A chamber con-structed of glass, Teflon , or other nonreac-tive material and designed to provide thor-ough mixing of reaction products and diluentair. The residence time is not critical whenthe dynamic parameter specification givenin 1.4 is met.

1.2.10 Output manifold. The output manifoldshould be constructed of glass, Teflon , orother non-reactive material and should be ofsufficient diameter to insure an insignificantpressure drop at the analyzer connection.The system must have a vent designed to in-sure atmospheric pressure at the manifoldand to prevent ambient air from entering themanifold.

1.3 Reagents.1.3.1 NO concentration standard. Gas cyl-

inder standard containing 50 to 100 ppm NOin N2 with less than 1 ppm NO2. This stand-ard must be traceable to a National Bureauof Standards (NBS) NO in N2 Standard Ref-erence Material (SRM 1683 or SRM 1684), anNBS NO2 Standard Reference Material (SRM1629), or an NBS/EPA-approved commerciallyavailable Certified Reference Material(CRM). CRM’s are described in Reference 14,and a list of CRM sources is available fromthe address shown for Reference 14. A rec-ommended protocol for certifying NO gascylinders against either an NO SRM or CRMis given in section 2.0.7 of Reference 15. Ref-erence 13 gives procedures for certifying anNO gas cylinder against an NBS NO2 SRMand for determining the amount of NO2 im-purity in an NO cylinder.

1.3.2 Zero air. Air, free of contaminantswhich will cause a detectable response on theNO/NOX/NO2 analyzer or which might reactwith either NO, O3, or NO2 in the gas phasetitration. A procedure for generating zero airis given in reference 13.

1.4 Dynamic parameter specification.1.4.1 The O3 generator air flowrate (F0) and

NO flowrate (FNO) (see Figure 1) must be ad-justed such that the following relationshipholds:

P tR RC R= ×[NO] 2.75 ppm-minutes (2)

[ ] [ ] ( )NO NO STDRCF

F F=

+

NO

O NO

3

tV

F FRRC

O

=+

<NO

2 minutes (4)

where:

PR = dynamic parameter specification, deter-mined empirically, to insure complete re-action of the available O3, ppm-minute

[NO]RC = NO concentration in the reactionchamber, ppm

R = residence time of the reactant gases inthe reaction chamber, minute

[NO]STD = concentration of the undiluted NOstandard, ppm

FNO = NO flowrate, scm 3/minFO = O3 generator air flowrate, scm 3/minVRC = volume of the reaction chamber, scm 3

1.4.2 The flow conditions to be used in theGPT system are determined by the followingprocedure:

(a) Determine FT, the total flow required atthe output manifold (FT=analyzer demandplus 10 to 50% excess).

(b) Establish [NO]OUT as the highest NOconcentration (ppm) which will be requiredat the output manifold. [NO]OUT should beapproximately equivalent to 90% of theupper range limit (URL) of the NO2 con-centration range to be covered.

(c) Determine FNO as

FNO F

NONOOUT T

STD

]

[ ]=

×[( )5

(d) Select a convenient or available reac-tion chamber volume. Initially, a trial VRC

may be selected to be in the range of ap-proximately 200 to 500 scm3.

(e) Compute FO as

(f) Compute tR as

tV

F FRRC=

+O NO

(7)

Verify that tR < 2 minutes. If not, select a re-action chamber with a smaller VRC.

(g) Compute the diluent air flowrate as

F F F FD T O= ' ' ( )NO 8where:

FD = diluent air flowrate, scm 3/min


48


(h) If FO turns out to be impractical for thedesired system, select a reaction chamberhaving a different VRC and recompute FO andFD.

NOTE: A dynamic parameter lower than2.75 ppm-minutes may be used if it can be de-termined empirically that quantitative reac-tion of O3 with NO occurs. A procedure formaking this determination as well as a moredetailed discussion of the above require-ments and other related considerations isgiven in reference 13.

1.5 Procedure.1.5.1 Assemble a dynamic calibration sys-

tem such as the one shown in Figure 1.1.5.2 Insure that all flowmeters are cali-

brated under the conditions of use against areliable standard such as a soap-bubblemeter or wet-test meter. All volumetricflowrates should be corrected to 25 °C and 760mm Hg. A discussion on the calibration offlowmeters is given in reference 13.

1.5.3 Precautions must be taken to removeO2 and other contaminants from the NO pres-sure regulator and delivery system prior tothe start of calibration to avoid any conver-sion of the standard NO to NO2. Failure to doso can cause significant errors in calibration.This problem may be minimized by (1) care-fully evacuating the regulator, when pos-sible, after the regulator has been connectedto the cylinder and before opening the cyl-inder valve; (2) thoroughly flushing the regu-lator and delivery system with NO afteropening the cylinder valve; (3) not removingthe regulator from the cylinder between cali-brations unless absolutely necessary. Fur-ther discussion of these procedures is givenin reference 13.

1.5.4 Select the operating range of the NO/NOX/NO2 analyzer to be calibrated. In orderto obtain maximum precision and accuracyfor NO2 calibration, all three channels of theanalyzer should be set to the same range. Ifoperation of the NO and NOX channels onhigher ranges is desired, subsequent re-calibration of the NO and NOX channels onthe higher ranges is recommended.

NOTE: Some analyzer designs may requireidentical ranges for NO, NOX, and NO2 duringoperation of the analyzer.

1.5.5 Connect the recorder output cable(s)of the NO/NOX/NO2 analyzer to the input ter-minals of the strip chart recorder(s). All ad-justments to the analyzer should be per-formed based on the appropriate strip chartreadings. References to analyzer responses inthe procedures given below refer to recorderresponses.

1.5.6 Determine the GPT flow conditionsrequired to meet the dynamic parameterspecification as indicated in 1.4.

1.5.7 Adjust the diluent air and O3 gener-ator air flows to obtain the flows determinedin section 1.4.2. The total air flow must ex-ceed the total demand of the analyzer(s) con-nected to the output manifold to insure that

no ambient air is pulled into the manifoldvent. Allow the analyzer to sample zero airuntil stable NO, NOX, and NO2 responses areobtained. After the responses have stabilized,adjust the analyzer zero control(s).

NOTE: Some analyzers may have separatezero controls for NO, NOX, and NO2. Otheranalyzers may have separate zero controlsonly for NO and NOX, while still others mayhave only one zero control common to allthree channels.

Offsetting the analyzer zero adjustmentsto +5 percent of scale is recommended to fa-cilitate observing negative zero drift. Recordthe stable zero air responses as ZNO, ZNOX,and ZNO2.

1.5.8 Preparation of NO and NOX calibrationcurves.

1.5.8.1 Adjustment of NO span control. Adjustthe NO flow from the standard NO cylinderto generate an NO concentration of approxi-mately 80 percent of the upper range limit(URL) of the NO range. This exact NO con-centration is calculated from:

[ ][ ]

( )NOF NO

F F FOUT

NO STD

NO O D

=×

+ +9

where:

[NO]OUT = diluted NO concentration at theoutput manifold, ppm

Sample this NO concentration until the NOand NOX responses have stabilized. Adjustthe NO span control to obtain a recorder re-sponse as indicated below:

recorder response (percent scale) =

[ ]( )

NO

URLZOUT

NO×

+100 10

where:

URL = nominal upper range limit of the NOchannel, ppmNOTE: Some analyzers may have separate

span controls for NO, NOX, and NO2. Otheranalyzers may have separate span controlsonly for NO and NOX, while still others mayhave only one span control common to allthree channels. When only one span controlis available, the span adjustment is made onthe NO channel of the analyzer.If substantial adjustment of the NO spancontrol is necessary, it may be necessary torecheck the zero and span adjustments by re-peating steps 1.5.7 and 1.5.8.1. Record the NOconcentration and the analyzer’s NO re-sponse.

1.5.8.2 Adjustment of NOX span control. Whenadjusting the analyzer’s NOX span control,the presence of any NO2 impurity in thestandard NO cylinder must be taken into ac-count. Procedures for determining theamount of NO2 impurity in the standard NO


49


cylinder are given in reference 13. The exactNOX concentration is calculated from:

[ ][ ] [ ]

( )NOF NO NO

F F FX OUT

NO STD IMP

NO O D

=× +( )

+ +

2 11

where:

[NOX]OUT = diluted NOX concentration at theoutput manifold, ppm

[NO2]IMP = concentration of NO2 impurity inthe standard NO cylinder, ppm

Adjust the NOX span control to obtain a re-corder response as indicated below:

recorder response (% scale) =

[ ]( )

NO

URLZX OUT

NOX×

+100 12

NOTE: If the analyzer has only one spancontrol, the span adjustment is made on theNO channel and no further adjustment ismade here for NOx.

If substantial adjustment of the NOX spancontrol is necessary, it may be necessary torecheck the zero and span adjustments by re-peating steps 1.5.7 and 1.5.8.2. Record theNOX concentration and the analyzer’s NOX

response.1.5.8.3 Generate several additional con-

centrations (at least five evenly spacedpoints across the remaining scale are sug-gested to verify linearity) by decreasing FNO

or increasing FD. For each concentrationgenerated, calculate the exact NO and NOX

concentrations using equations (9) and (11)respectively. Record the analyzer’s NO andNOX responses for each concentration. Plotthe analyzer responses versus the respectivecalculated NO and NOX concentrations anddraw or calculate the NO and NOX calibra-tion curves. For subsequent calibrationswhere linearity can be assumed, these curvesmay be checked with a two-point calibrationconsisting of a zero air point and NO andNOX concentrations of approximately 80% ofthe URL.

1.5.9 Preparation of NO2 calibration curve.1.5.9.1 Assuming the NO2 zero has been

properly adjusted while sampling zero air instep 1.5.7, adjust FO and FD as determined insection 1.4.2. Adjust FNO to generate an NOconcentration near 90% of the URL of the NOrange. Sample this NO concentration untilthe NO and NOX responses have stabilized.Using the NO calibration curve obtained insection 1.5.8, measure and record the NO con-centration as [NO]orig. Using the NOX cali-bration curve obtained in section 1.5.8, meas-ure and record the NOX concentration as[NOX]orig.

1.5.9.2 Adjust the O3 generator to generatesufficient O3 to produce a decrease in the NOconcentration equivalent to approximately80% of the URL of the NO2 range. The de-crease must not exceed 90% of the NO con-centration determined in step 1.5.9.1. Afterthe analyzer responses have stabilized,record the resultant NO and NOX concentra-tions as [NO]rem and [NOX]rem.

1.5.9.3 Calculate the resulting NO2 con-centration from:

[ ] [ ] [ ]]

( )NO NO NOOUT orig remIMP

2 13= − +×

+ +

F

F F F

NO

NO O D

[NO2

where:

[NO2]OUT = diluted NO2 concentration at theoutput manifold, ppm

[NO]orig = original NO concentration, priorto addition of O3, ppm

[NO]rem = NO concentration remaining afteraddition of O3, ppm

Adjust the NO2 span control to obtain a re-corder response as indicated below:

recorder response (% scale)=

[ ]( )

NOZOUT

NO2 100 14

2URL

×

+

NOTE: If the analyzer has only one or twospan controls, the span adjustments aremade on the NO channel or NO and NOX

channels and no further adjustment is madehere for NO2.

If substantial adjustment of the NO2 spancontrol is necessary, it may be necessary torecheck the zero and span adjustments by re-peating steps 1.5.7 and 1.5.9.3. Record the NO2

concentration and the corresponding ana-lyzer NO2 and NOX responses.

1.5.9.4 Maintaining the same FNO, FO, andFD as in section 1.5.9.1, adjust the ozone gen-erator to obtain several other concentrationsof NO2 over the NO2 range (at least five even-ly spaced points across the remaining scaleare suggested). Calculate each NO2 con-centration using equation (13) and record thecorresponding analyzer NO2 and NOX re-sponses. Plot the analyzer’s NO2 responsesversus the corresponding calculated NO2 con-centrations and draw or calculate the NO2

calibration curve.1.5.10 Determination of converter efficiency.


50


1.5.10.1 For each NO2 concentration gen-erated during the preparation of the NO2

calibration curve (see section 1.5.9) calculatethe concentration of NO2 converted from:

NO NO NO NOCONV OUT X orig X rem2 2 15[ ] = [ ] [ ] [ ]( )' ' ( )

where:[NO2]CONV = concentration of NO2 converted,

ppm[NOX]orig = original NOX concentration prior

to addition of O3, ppm[NOX]rem = NOX concentration remaining

after addition of O3, ppm

NOTE: Supplemental information on cali-bration and other procedures in this methodare given in reference 13.Plot [NO2]CONV (y-axis) versus [NO2]OUT (x-axis) and draw or calculate the converter ef-ficiency curve. The slope of the curve times100 is the average converter efficiency, EC.

The average converter efficiency must begreater than 96%; if it is less than 96%, re-place or service the converter.

2. Alternative B—NO2 permeation device.Major equipment required:Stable O3 generator.Chemiluminescence NO/NOX/NO2 analyzer

with strip chart recorder(s).NO concentration standard.NO2 concentration standard.2.1 Principle. Atmospheres containing accu-

rately known concentrations of nitrogen di-oxide are generated by means of a perme-ation device. (10) The permeation deviceemits NO2 at a known constant rate providedthe temperature of the device is held con-stant (±0.1 °C) and the device has been accu-rately calibrated at the temperature of use.The NO2 emitted from the device is dilutedwith zero air to produce NO2 concentrationssuitable for calibration of the NO2 channel ofthe NO/NOX/NO2 analyzer. An NO concentra-tion standard is used for calibration of theNO and NOX channels of the analyzer.

2.2 Apparatus. A typical system suitable forgenerating the required NO and NO2 con-centrations is shown in Figure 2. All connec-tions between components downstream fromthe permeation device should be of glass,Teflon , or other non-reactive material.

2.2.1 Air flow controllers. Devices capable ofmaintaining constant air flows within ±2% ofthe required flowrate.

2.2.2 NO flow controller. A device capable ofmaintaining constant NO flows within ±2%of the required flowrate. Component parts incontact with the NO must be of a non-reac-tive material.

2.2.3 Air flowmeters. Calibrated flowmeterscapable of measuring and monitoring airflowrates with an accuracy of ±2% of themeasured flowrate.

2.2.4 NO flowmeter. A calibrated flowmetercapable of measuring and monitoring NOflowrates with an accuracy of ±2% of themeasured flowrate. (Rotameters have beenreported to operate unreliably when meas-uring low NO flows and are not rec-ommended.)

2.2.5 Pressure regulator for standard NO cyl-inder. This regulator must have a non-reac-tive diaphragm and internal parts and a suit-able delivery pressure.

2.2.6 Drier. Scrubber to remove moisturefrom the permeation device air system. Theuse of the drier is optional with NO2 perme-ation devices not sensitive to moisture.(Refer to the supplier’s instructions for useof the permeation device.)

2.2.7 Constant temperature chamber. Cham-ber capable of housing the NO2 permeationdevice and maintaining its temperature towithin ±0.1 °C.

2.2.8 Temperature measuring device. Devicecapable of measuring and monitoring thetemperature of the NO2 permeation devicewith an accuracy of ±0.05 °C.

2.2.9 Valves. A valve may be used as shownin Figure 2 to divert the NO2 from the perme-ation device when zero air or NO is requiredat the manifold. A second valve may be usedto divert the NO flow when zero air or NO2 isrequired at the manifold.

The valves should be constructed of glass,Teflon , or other nonreactive material.

2.2.10 Mixing chamber. A chamber con-structed of glass, Teflon , or other nonreac-tive material and designed to provide thor-ough mixing of pollutant gas streams anddiluent air.

2.2.11 Output manifold. The output manifoldshould be constructed of glass, Teflon , orother non-reactive material and should be ofsufficient diameter to insure an insignificantpressure drop at the analyzer connection.The system must have a vent designed to in-sure atmospheric pressure at the manifoldand to prevent ambient air from entering themanifold.

2.3 Reagents.2.3.1 Calibration standards. Calibration

standards are required for both NO and NO2.

The reference standard for the calibrationmay be either an NO or NO2 standard, andmust be traceable to a National Bureau ofStandards (NBS) NO in N2 Standard Ref-erence Material (SRM 1683 or SRM 1684), andNBS NO2 Standard Reference Material (SRM1629), or an NBS/EPA-approved commercially


51


available Certified Reference Material(CRM). CRM’s are described in Reference 14,and a list of CRM sources is available fromthe address shown for Reference 14. Ref-erence 15 gives recommended procedures forcertifying an NO gas cylinder against an NOSRM or CRM and for certifying an NO2 per-meation device against an NO2 SRM. Ref-erence 13 contains procedures for certifyingan NO gas cylinder against an NO2 SRM andfor certifying an NO2 permeation deviceagainst an NO SRM or CRM. A procedure fordetermining the amount of NO2 impurity inan NO cylinder is also contained in Ref-erence 13. The NO or NO2 standard selectedas the reference standard must be used tocertify the other standard to ensure consist-ency between the two standards.

2.3.1.1 NO2 Concentration standard. A perme-ation device suitable for generating NO2 con-centrations at the required flow-rates overthe required concentration range. If the per-meation device is used as the referencestandard, it must be traceable to an SRM orCRM as specified in 2.3.1. If an NO cylinder isused as the reference standard, the NO2 per-meation device must be certified against theNO standard according to the proceduregiven in Reference 13. The use of the perme-ation device should be in strict accordancewith the instructions supplied with the de-vice. Additional information regarding theuse of permeation devices is given byScaringelli et al. (11) and Rook et al. (12).

2.3.1.2 NO Concentration standard. Gas cyl-inder containing 50 to 100 ppm NO in N2 withless than 1 ppm NO2. If this cylinder is usedas the reference standard, the cylinder mustbe traceable to an SRM or CRM as specifiedin 2.3.1. If an NO2 permeation device is usedas the reference standard, the NO cylindermust be certified against the NO2 standardaccording to the procedure given in Ref-erence 13. The cylinder should be recertifiedon a regular basis as determined by the localquality control program.

2.3.3 Zero air. Air, free of contaminantswhich might react with NO or NO2 or causea detectable response on the NO/NOX/NO2 an-alyzer. When using permeation devices thatare sensitive to moisture, the zero air pass-ing across the permeation device must be dryto avoid surface reactions on the device.(Refer to the supplier’s instructions for useof the permeation device.) A procedure forgenerating zero air is given in reference 13.

2.4 Procedure.2.4.1 Assemble the calibration apparatus

such as the typical one shown in Figure 2.2.4.2 Insure that all flowmeters are cali-

brated under the conditions of use against areliable standard such as a soap bubblemeter or wet-test meter. All volumetricflowrates should be corrected to 25 °C and 760mm Hg. A discussion on the calibration offlowmeters is given in reference 13.

2.4.3 Install the permeation device in theconstant temperature chamber. Provide asmall fixed air flow (200–400 scm 3/min) acrossthe device. The permeation device should al-ways have a continuous air flow across it toprevent large buildup of NO2 in the systemand a consequent restabilization period.Record the flowrate as FP. Allow the deviceto stabilize at the calibration temperaturefor at least 24 hours. The temperature mustbe adjusted and controlled to within ±0.1 °Cor less of the calibration temperature asmonitored with the temperature measuringdevice.

2.4.4 Precautions must be taken to removeO2 and other contaminants from the NO pres-sure regulator and delivery system prior tothe start of calibration to avoid any conver-sion of the standard NO to NO2. Failure to doso can cause significant errors in calibration.This problem may be minimized by

(1) Carefully evacuating the regulator,when possible, after the regulator has beenconnected to the cylinder and before openingthe cylinder valve;

(2) Thoroughly flushing the regulator anddelivery system with NO after opening thecylinder valve;

(3) Not removing the regulator from thecylinder between calibrations unless abso-lutely necessary. Further discussion of theseprocedures is given in reference 13.

2.4.5 Select the operating range of the NO/NOX NO2 analyzer to be calibrated. In orderto obtain maximum precision and accuracyfor NO2 calibration, all three channels of theanalyzer should be set to the same range. Ifoperation of the NO and NOX channels onhigher ranges is desired, subsequent re-calibration of the NO and NOX channels onthe higher ranges is recommended.

NOTE: Some analyzer designs may requireidentical ranges for NO, NOX, and NO2 duringoperation of the analyzer.

2.4.6 Connect the recorder output cable(s)of the NO/NOX/NO2 analyzer to the input ter-minals of the strip chart recorder(s). All ad-justments to the analyzer should be per-formed based on the appropriate strip chartreadings. References to analyzer responses inthe procedures given below refer to recorderresponses.

2.4.7 Switch the valve to vent the flow fromthe permeation device and adjust the diluentair flowrate, FD, to provide zero air at theoutput manifold. The total air flow must ex-ceed the total demand of the analyzer(s) con-nected to the output manifold to insure thatno ambient air is pulled into the manifoldvent. Allow the analyzer to sample zero airuntil stable NO, NOX, and NO2 responses areobtained. After the responses have stabilized,adjust the analyzer zero control(s).

NOTE: Some analyzers may have separatezero controls for NO, NOX, and NO2. Otheranalyzers may have separate zero controlsonly for NO and NOX, while still others may


52


have only one zero common control to allthree channels.Offsetting the analyzer zero adjustments to+5% of scale is recommended to facilitate ob-serving negative zero drift. Record the stablezero air responses as ZNO, ZNOX, and ZNO2.

2.4.8 Preparation of NO and NOX calibrationcurves.

2.4.8.1 Adjustment of NO span control. Adjustthe NO flow from the standard NO cylinderto generate an NO concentration of approxi-mately 80% of the upper range limit (URL) ofthe NO range. The exact NO concentration iscalculated from:

[ ][ ]

( )NOF NO

F FOUT

NO STD

NO D

=×

+16

where:

[NO]OUT = diluted NO concentration at theoutput manifold, ppm

FNO = NO flowrate, scm3/min[NO]STD=concentration of the undiluted NO

standard, ppmFD = diluent air flowrate, scm 3/min

Sample this NO concentration until the NOand NOX responses have stabilized. Adjustthe NO span control to obtain a recorder re-sponse as indicated below:

recorder response (% scale)=

= ×

+

[ ]( )

NOZOUT

NOURL

100 17

=[ ]

×

+

NOZ

X OUTNOXURL

100 19( )

where:

URL = nominal upper range limit of the NOchannel, ppmNOTE: Some analyzers may have separate

span controls for NO, NOX, and NO2. Otheranalyzers may have separate span controlsonly for NO and NOX, while still others mayhave only one span control common to allthree channels. When only one span controlis available, the span adjustment is made onthe NO channel of the analyzer.If substantial adjustment of the NO spancontrol is necessary, it may be necessary torecheck the zero and span adjustments by re-peating steps 2.4.7 and 2.4.8.1. Record the NOconcentration and the analyzer’s NO re-sponse.

2.4.8.2 Adjustment of NOX span control. Whenadjusting the analyzer’s NOX span control,the presence of any NO2 impurity in thestandard NO cylinder must be taken into ac-count. Procedures for determining theamount of NO2 impurity in the standard NO

cylinder are given in reference 13. The exactNOX concentration is calculated from:

[ ][ ] [ ]

( )NOF NO NO

F FOUT

NO STD IMP

NO D

X =× +( )

+

2 18

where:[NOX]OUT = diluted NOX cencentration at the

output manifold, ppm[NO2]IMP = concentration of NO2 impurity in

the standard NO cylinder, ppm

Adjust the NOX span control to obtain a con-venient recorder response as indicated below:

recorder response (% scale)

= ×

+

[ ]( )

NOZX OUT

NOURL

X100 19

NOTE: If the analyzer has only one spancontrol, the span adjustment is made on theNO channel and no further adjustment ismade here for NOX.If substantial adjustment of the NOX spancontrol is necessary, it may be necessary torecheck the zero and span adjustments by re-peating steps 2.4.7 and 2.4.8.2. Record theNOX concentration and the analyzer’s NOX

response.2.4.8.3 Generate several additional con-

centrations (at least five evenly spacedpoints across the remaining scale are sug-gested to verify linearity) by decreasing FNO

or increasing FD. For each concentrationgenerated, calculate the exact NO and NOX

concentrations using equations (16) and (18)respectively. Record the analyzer’s NO andNOX responses for each concentration. Plotthe analyzer responses versus the respectivecalculated NO and NOX concentrations anddraw or calculate the NO and NOX calibra-tion curves. For subsequent calibrationswhere linearity can be assumed, these curvesmay be checked with a two-point calibrationconsisting of a zero point and NO and NOX

concentrations of approximately 80 percentof the URL.

2.4.9 Preparation of NO2 calibration curve.2.4.9.1 Remove the NO flow. Assuming the

NO2 zero has been properly adjusted whilesampling zero air in step 2.4.7, switch thevalve to provide NO2 at the output manifold.

2.4.9.2 Adjust FD to generate an NO2 con-centration of approximately 80 percent of theURL of the NO2 range. The total air flowmust exceed the demand of the analyzer(s)under calibration. The actual concentrationof NO2 is calculated from:

[ ] ( )NOR K

F FOUT

P D

2 20=×

+

where:


53


[NO2]OUT = diluted NO2 concentration at theoutput manifold, ppm

R = permeation rate, µg/minK = 0.532µl NO2/µg NO2 (at 25 °C and 760 mm

Hg)Fp = air flowrate across permeation device,

scm 3/minFD = diluent air flowrate, scm 3/min

Sample this NO2 concentration until theNOX and NO2 responses have stabilized. Ad-just the NO2 span control to obtain a re-corder response as indicated below:

recorder response (% scale)

= ×

+

[ ]( )

NOZOUT

NO2

2100 21URL

NOTE: If the analyzer has only one or twospan controls, the span adjustments aremade on the NO channel or NO and NOX

channels and no further adjustment is madehere for NO2.

If substantial adjustment of the NO2 spancontrol is necessary it may be necessary torecheck the zero and span adjustments by re-peating steps 2.4.7 and 2.4.9.2. Record the NO2

concentration and the analyzer’s NO2 re-sponse. Using the NOX calibration curve ob-tained in step 2.4.8, measure and record theNOX concentration as [NOX]M.

2.4.9.3 Adjust FD to obtain several otherconcentrations of NO2 over the NO2 range (atleast five evenly spaced points across the re-maining scale are suggested). Calculate eachNO2 concentration using equation (20) andrecord the corresponding analyzer NO2 andNOX responses. Plot the analyzer’s NO2 re-sponses versus the corresponding calculatedNO2 concentrations and draw or calculatethe NO2 calibration curve.

2.4.10 Determination of converter efficiency.2.4.10.1 Plot [NOX]M (y-axis) versus

[NO2]OUT (x-axis) and draw or calculate theconverter efficiency curve. The slope of thecurve times 100 is the average converter effi-ciency, EC. The average converter efficiencymust be greater than 96 percent; if it is lessthan 96 percent, replace or service the con-verter.

NOTE: Supplemental information on cali-bration and other procedures in this methodare given in reference 13.

3. Frequency of calibration. The frequency ofcalibration, as well as the number of pointsnecessary to establish the calibration curveand the frequency of other performancechecks, will vary from one analyzer to an-other. The user’s quality control programshould provide guidelines for initial estab-lishment of these variables and for subse-quent alteration as operational experience isaccumulated. Manufacturers of analyzersshould include in their instruction/operationmanuals information and guidance as to

these variables and on other matters of oper-ation, calibration, and quality control.

REFERENCES

1. A. Fontijn, A. J. Sabadell, and R. J.Ronco, ‘‘Homogeneous ChemiluminescentMeasurement of Nitric Oxide with Ozone,’’Anal. Chem., 42, 575 (1970).

2. D. H. Stedman, E. E. Daby, F. Stuhl, andH. Niki, ‘‘Analysis of Ozone and Nitric Oxideby a Chemiluminiscent Method in Labora-tory and Atmospheric Studies of Photo-chemical Smog,’’ J. Air Poll. Control Assoc.,22, 260 (1972).

3. B. E. Martin, J. A. Hodgeson, and R. K.Stevens, ‘‘Detection of Nitric OxideChemiluminescence at Atmospheric Pres-sure,’’ Presented at 164th National ACSMeeting, New York City, August 1972.

4. J. A. Hodgeson, K. A. Rehme, B. E. Mar-tin, and R. K. Stevens, ‘‘Measurements forAtmospheric Oxides of Nitrogen and Ammo-nia by Chemiluminescence,’’ Presented at1972 APCA Meeting, Miami, FL, June 1972.

5. R. K. Stevens and J. A. Hodgeson, ‘‘Ap-plications of Chemiluminescence Reactionsto the Measurement of Air Pollutants,’’Anal. Chem., 45, 443A (1973).

6. L. P. Breitenbach and M. Shelef, ‘‘Devel-opment of a Method for the Analysis of NO2

and NH3 by NO-Measuring Instruments,’’ J.Air Poll. Control Assoc., 23, 128 (1973).

7. A. M. Winer, J. W. Peters, J. P. Smith,and J. N. Pitts, Jr., ‘‘Response of Commer-cial Chemiluminescent NO-NO2 Analyzers toOther Nitrogen-Containing Compounds,’’ En-viron. Sci. Technol., 8, 1118 (1974).

8. K. A. Rehme, B. E. Martin, and J. A.Hodgeson, Tentative Method for the Calibra-tion of Nitric Oxide, Nitrogen Dioxide, andOzone Analyzers by Gas Phase Titration,’’EPA–R2–73–246, March 1974.

9. J. A. Hodgeson, R. K. Stevens, and B. E.Martin, ‘‘A Stable Ozone Source Applicableas a Secondary Standard for Calibration ofAtmospheric Monitors,’’ ISA Transactions,11, 161 (1972).

10. A. E. O’Keeffe and G. C. Ortman, ‘‘Pri-mary Standards for Trace Gas Analysis,’’Anal. Chem., 38, 760 (1966).

11. F. P. Scaringelli, A. E. O’Keeffe, E.Rosenberg, and J. P. Bell, ‘‘Preparation ofKnown Concentrations of Gases and Vaporswith Permeation Devices Calibrated Gravi-metrically,’’ Anal. Chem., 42, 871 (1970).

12. H. L. Rook, E. E. Hughes, R. S. Fuerst,and J. H. Margeson, ‘‘Operation Characteris-tics of NO2 Permeation Devices,’’ Presentedat 167th National ACS Meeting, Los Angeles,CA, April 1974.

13. E. C. Ellis, ‘‘Technical Assistance Docu-ment for the Chemiluminescence Measure-ment of Nitrogen Dioxide,’’ EPA–E600/4–75–003 (Available in draft form from the UnitedStates Environmental Protection Agency,


54


Department E (MD–76), Environmental Moni-toring and Support Laboratory, ResearchTriangle Park, NC 27711).

14. A Procedure for EstablishingTraceability of Gas Mixtures to Certain Na-tional Bureau of Standards Standard Ref-erence Materials. EPA–600/7–81–010, Jointpublication by NBS and EPA. Available fromthe U.S. Environmental Protection Agency,Environmental Monitoring Systems Labora-

tory (MD–77), Research Triangle Park, NC27711, May 1981.

15. Quality Assurance Handbook for Air Pol-lution Measurement Systems, Volume II, Ambi-ent Air Specific Methods. The U.S. Environ-mental Protection Agency, EnvironmentalMonitoring Systems Laboratory, ResearchTriangle Park, NC 27711. Publication No.EAP–600/4–77–027a.


55

Environmental Protection Agency Pt. 50, App. G

[41 FR 52688, Dec. 1, 1976, as amended at 48 FR 2529, Jan 20, 1983]

APPENDIX G TO PART 50—REFERENCEMETHOD FOR THE DETERMINATION OFLEAD IN SUSPENDED PARTICULATEMATTER COLLECTED FROM AMBIENTAIR

1. Principle and applicability.1.1 Ambient air suspended particulate mat-

ter is collected on a glass-fiber filter for 24hours using a high volume air sampler. Theanalysis of the 24-hour samples may be per-formed for either individual samples or com-posites of the samples collected over a cal-endar month or quarter, provided that thecompositing procedure has been approved inaccordance with section 2.8 of appendix C topart 58 of this chapter—Modifications of meth-ods by users. (Guidance or assistance in re-questing approval under Section 2.8 can beobtained from the address given in section2.7 of appendix C to part 58 of this chapter.)

1.2 Lead in the particulate matter is solu-bilized by extraction with nitric acid (HNO3),facilitated by heat or by a mixture of HNO3

and hydrochloric acid (HCl) facilitated byultrasonication.

1.3 The lead content of the sample is ana-lyzed by atomic absorption spectrometryusing an air-acetylene flame, the 283.3 or217.0 nm lead absorption line, and the opti-mum instrumental conditions recommendedby the manufacturer.

1.4 The ultrasonication extraction withHNO3/HCl will extract metals other than leadfrom ambient particulate matter.

2. Range, sensitivity, and lower detectablelimit. The values given below are typical ofthe methods capabilities. Absolute valueswill vary for individual situations dependingon the type of instrument used, the lead line,and operating conditions.

2.1 Range. The typical range of the methodis 0.07 to 7.5 µg Pb/m3 assuming an upper lin-ear range of analysis of 15 µg/ml and an airvolume of 2,400 m3.

2.2 Sensitivity. Typical sensitivities for a 1percent change in absorption (0.0044 absorb-ance units) are 0.2 and 0.5 µg Pb/ml for the217.0 and 283.3 nm lines, respectively.

2.3 Lower detectable limit (LDL). A typicalLDL is 0.07 µg Pb/m3. The above value wascalculated by doubling the between-labora-tory standard deviation obtained for the low-est measurable lead concentration in a col-laborative test of the method.(15) An air vol-ume of 2,400 m3 was assumed.

3. Interferences. Two types of interferencesare possible: chemical and light scattering.

3.1 Chemical. Reports on the absence (1, 2, 3,4, 5) of chemical interferences far outweighthose reporting their presence, (6) therefore,no correction for chemical interferences isgiven here. If the analyst suspects that thesample matrix is causing a chemical inter-ference, the interference can be verified andcorrected for by carrying out the analysiswith and without the method of standard ad-ditions.(7)


56

40 CFR Ch. I (7–1–01 Edition)Pt. 50, App. G

1 Mention of commercial products does notimply endorsement by the U.S. Environ-mental Protection Agency.

3.2 Light scattering. Nonatomic absorptionor light scattering, produced by high con-centrations of dissolved solids in the sample,can produce a significant interference, espe-cially at low lead concentrations. (2) The in-terference is greater at the 217.0 nm linethan at the 283.3 nm line. No interferencewas observed using the 283.3 nm line with asimilar method.(1)

Light scattering interferences can, how-ever, be corrected for instrumentally. Sincethe dissolved solids can vary depending onthe origin of the sample, the correction maybe necessary, especially when using the 217.0nm line. Dual beam instruments with a con-tinuum source give the most accurate cor-rection. A less accurate correction can be ob-tained by using a nonabsorbing lead line thatis near the lead analytical line. Informationon use of these correction techniques can beobtained from instrument manufacturers’manuals.

If instrumental correction is not feasible,the interference can be eliminated by use ofthe ammonium pyrrolidinecarbodithioate-methylisobutyl ketone, chelation-solvent ex-traction technique of sample preparation.(8)

4. Precision and bias.4.1 The high-volume sampling procedure

used to collect ambient air particulate mat-ter has a between-laboratory relative stand-ard deviation of 3.7 percent over the range 80to 125 µg/m3.(9) The combined extraction-analysis procedure has an average within-laboratory relative standard deviation of 5 to6 percent over the range 1.5 to 15 µg Pb/ml,and an average between laboratory relativestandard deviation of 7 to 9 percent over thesame range. These values include use of ei-ther extraction procedure.

4.2 Single laboratory experiments and col-laborative testing indicate that there is nosignificant difference in lead recovery be-tween the hot and ultrasonic extraction pro-cedures.(15)

5. Apparatus.5.1 Sampling.5.1.1 High-Volume Sampler. Use and cali-

brate the sampler as described in appendix Bto this part.

5.2 Analysis.5.2.1 Atomic absorption spectrophotometer.

Equipped with lead hollow cathode orelectrodeless discharge lamp.

5.2.1.1 Acetylene. The grade recommendedby the instrument manufacturer should beused. Change cylinder when pressure dropsbelow 50–100 psig.

5.2.1.2 Air. Filtered to remove particulate,oil, and water.

5.2.2 Glassware. Class A borosilicate glass-ware should be used throughout the analysis.

5.2.2.1 Beakers. 30 and 150 ml. graduated,Pyrex.

5.2.2.2 Volumetric flasks. 100-ml.5.2.2.3 Pipettes. To deliver 50, 30, 15, 8, 4, 2,

1 ml.

5.2.2.4 Cleaning. All glassware should bescrupulously cleaned. The following proce-dure is suggested. Wash with laboratory de-tergent, rinse, soak for 4 hours in 20 percent(w/w) HNO3, rinse 3 times with distilled-de-ionized water, and dry in a dust free manner.

5.2.3 Hot plate.5.2.4. Ultrasonication water bath, unheated.

Commercially available laboratory ultra-sonic cleaning baths of 450 watts or higher‘‘cleaning power,’’ i.e., actual ultrasonicpower output to the bath have been foundsatisfactory.

5.2.5 Template. To aid in sectioning theglass-fiber filter. See figure 1 for dimensions.

5.2.6 Pizza cutter. Thin wheel. Thickness1mm.

5.2.7 Watch glass.5.2.8 Polyethylene bottles. For storage of

samples. Linear polyethylene gives betterstorage stability than other polyethylenesand is preferred.

5.2.9 Parafilm ‘‘M’’.1 American Can Co.,Marathon Products, Neenah, Wis., or equiva-lent.

6. Reagents.6.1 Sampling.6.1.1 Glass fiber filters. The specifications

given below are intended to aid the user inobtaining high quality filters with reproduc-ible properties. These specifications havebeen met by EPA contractors.

6.1.1.1 Lead content. The absolute lead con-tent of filters is not critical, but low valuesare, of course, desirable. EPA typically ob-tains filters with a lead content of 75 µg/fil-ter.

It is important that the variation in leadcontent from filter to filter, within a givenbatch, be small.

6.1.1.2 Testing.6.1.1.2.1 For large batches of filters (>500

filters) select at random 20 to 30 filters froma given batch. For small batches (>500 fil-ters) a lesser number of filters may be taken.Cut one 3⁄4″×8″ strip from each filter any-where in the filter. Analyze all strips, sepa-rately, according to the directions in sec-tions 7 and 8.

6.1.1.2.2 Calculate the total lead in each fil-ter as

F g Pb mlb = × ×µ /100 ml

strip

12 strips

filterwhere:Fb = Amount of lead per 72 square inches of

filter, µg.

6.1.1.2.3 Calculate the mean, Fb, of the val-ues and the relative standard deviation(standard deviation/mean × 100). If the rel-ative standard deviation is high enough so


57


that, in the analysts opinion, subtraction ofFb, (section 10.3) may result in a significanterror in the µg Pb/m3, the batch should be re-jected.

6.1.1.2.4 For acceptable batches, use thevalue of Fb to correct all lead analyses (sec-tion 10.3) of particulate matter collectedusing that batch of filters. If the analysesare below the LDL (section 2.3) no correctionis necessary.

6.2 Analysis.6.2.1 Concentrated (15.6 M) HNO3. ACS rea-

gent grade HNO3 and commercially availableredistilled HNO3 has found to have suffi-ciently low lead concentrations.

6.2.2 Concentrated (11.7 M) HCl. ACS rea-gent grade.

6.2.3 Distilled-deionized water. (D.I. water).6.2.4 3 M HNO3. This solution is used in the

hot extraction procedure. To prepare, add 192ml of concentrated HNO3 to D.I. water in a 1l volumetric flask. Shake well, cool, and di-lute to volume with D.I. water. Caution: Ni-tric acid fumes are toxic. Prepare in a wellventilated fume hood.

6.2.5 0.45 M HNO3. This solution is used asthe matrix for calibration standards whenusing the hot extraction procedure. To pre-pare, add 29 ml of concentrated HNO3 to D.I.water in a 1 l volumetric flask. Shake well,cool, and dilute to volume with D.I. water.

6.2.6 2.6 M HNO3+0 to 0.9 M HCl. This solu-tion is used in the ultrasonic extraction pro-cedure. The concentration of HCl can be var-ied from 0 to 0.9 M. Directions are given forpreparation of a 2.6 M HNO3+0.9 M HCl solu-tion. Place 167 ml of concentrated HNO3 intoa 1 l volumetric flask and add 77 ml of con-centrated HCl. Stir 4 to 6 hours, dilute tonearly 1 l with D.I. water, cool to room tem-perature, and dilute to 1 l.

6.2.7 0.40 M HNO3 + X M HCl. This solutionis used as the matrix for calibration stand-ards when using the ultrasonic extractionprocedure. To prepare, add 26 ml of con-centrated HNO3, plus the ml of HCl required,to a 1 l volumetric flask. Dilute to nearly 1l with D.I. water, cool to room temperature,and dilute to 1 l. The amount of HCl requiredcan be determined from the following equa-tion:

y = × ×77 ml 0.15

0.9 Mwhere:

y = ml of concentrated HCl required.x = molarity of HCl in 6.2.6.0.15 = dilution factor in 7.2.2.

6.2.8 Lead nitrate, Pb(NO3)2. ACS reagentgrade, purity 99.0 percent. Heat for 4 hours at120 °C and cool in a desiccator.

6.3 Calibration standards.6.3.1 Master standard, 1000 µg Pb/ml in

HNO3. Dissolve 1.598 g of Pb(NO3)2 in 0.45 M

HNO3 contained in a 1 l volumetric flask anddilute to volume with 0.45 M HNO3.

6.3.2 Master standard, 1000 µg Pb/ml inHNO3/HCl. Prepare as in section 6.3.1 exceptuse the HNO3/HCl solution in section 6.2.7.

Store standards in a polyethylene bottle.Commercially available certified lead stand-ard solutions may also be used.

7. Procedure.7.1 Sampling. Collect samples for 24 hours

using the procedure described in reference 10with glass-fiber filters meeting the specifica-tions in section 6.1.1. Transport collectedsamples to the laboratory taking care tominimize contamination and loss of sam-ple. (16).

7.2 Sample preparation.7.2.1 Hot extraction procedure.7.2.1.1 Cut a 3⁄4″×8″ strip from the exposed

filter using a template and a pizza cutter asdescribed in Figures 1 and 2. Other cuttingprocedures may be used.

Lead in ambient particulate matter col-lected on glass fiber filters has been shownto be uniformly distributed across the fil-ter.1, 3, 11 Another study 12 has shown thatwhen sampling near a roadway, strip posi-tion contributes significantly to the overallvariability associated with lead analyses.Therefore, when sampling near a roadway,additional strips should be analyzed to mini-mize this variability.

7.2.1.2 Fold the strip in half twice and placein a 150-ml beaker. Add 15 ml of 3 M HNO3 tocover the sample. The acid should com-pletely cover the sample. Cover the beakerwith a watch glass.

7.2.1.3 Place beaker on the hot-plate, con-tained in a fume hood, and boil gently for 30min. Do not let the sample evaporate to dry-ness. Caution: Nitric acid fumes are toxic.

7.2.1.4 Remove beaker from hot plate andcool to near room temperature.

7.2.1.5 Quantitatively transfer the sampleas follows:

7.2.1.5.1 Rinse watch glass and sides ofbeaker with D.I. water.

7.2.1.5.2 Decant extract and rinsings into a100-ml volumetric flask.

7.2.1.5.3 Add D.I. water to 40 ml mark onbeaker, cover with watch glass, and set asidefor a minimum of 30 minutes. This is a crit-ical step and cannot be omitted since it al-lows the HNO3 trapped in the filter to diffuseinto the rinse water.

7.2.1.5.4 Decant the water from the filterinto the volumetric flask.

7.2.1.5.5 Rinse filter and beaker twice withD.I. water and add rinsings to volumetricflask until total volume is 80 to 85 ml.

7.2.1.5.6 Stopper flask and shake vigor-ously. Set aside for approximately 5 minutesor until foam has dissipated.

7.2.1.5.7 Bring solution to volume with D.I.water. Mix thoroughly.

7.2.1.5.8 Allow solution to settle for onehour before proceeding with analysis.


58


7.2.1.5.9 If sample is to be stored for subse-quent analysis, transfer to a linear poly-ethylene bottle.

7.2.2 Ultrasonic extraction procedure.7.2.2.1 Cut a 3⁄4″×8″ strip from the exposed

filter as described in section 7.2.1.1.7.2.2.2 Fold the strip in half twice and place

in a 30 ml beaker. Add 15 ml of the HNO3/HClsolution in section 6.2.6. The acid shouldcompletely cover the sample. Cover thebeaker with parafilm.

The parafilm should be placed over thebeaker such that none of the parafilm is incontact with water in the ultrasonic bath.Otherwise, rinsing of the parafilm (section7.2.2.4.1) may contaminate the sample.

7.2.2.3 Place the beaker in theultrasonication bath and operate for 30 min-utes.

7.2.2.4 Quantitatively transfer the sampleas follows:

7.2.2.4.1 Rinse parafilm and sides of beakerwith D.I. water.

7.2.2.4.2 Decant extract and rinsings into a100 ml volumetric flask.

7.2.2.4.3 Add 20 ml D.I. water to cover thefilter strip, cover with parafilm, and setaside for a minimum of 30 minutes. This is acritical step and cannot be omitted. Thesample is then processed as in sections7.2.1.5.4 through 7.2.1.5.9.

NOTE: Samples prepared by the hot extrac-tion procedure are now in 0.45 M HNO3. Sam-ples prepared by the ultrasonication proce-dure are in 0.40 M HNO3 +X M HCl.

8. Analysis.8.1 Set the wavelength of the

monochromator at 283.3 or 217.0 nm. Set oralign other instrumental operating condi-tions as recommended by the manufacturer.

8.2 The sample can be analyzed directlyfrom the volumetric flask, or an appropriateamount of sample decanted into a sampleanalysis tube. In either case, care should betaken not to disturb the settled solids.

8.3 Aspirate samples, calibration standardsand blanks (section 9.2) into the flame andrecord the equilibrium absorbance.

8.4 Determine the lead concentration in µgPb/ml, from the calibration curve, section9.3.

8.5 Samples that exceed the linear calibra-tion range should be diluted with acid of thesame concentration as the calibration stand-ards and reanalyzed.

9. Calibration.9.1 Working standard, 20 µg Pb/ml. Prepared

by diluting 2.0 ml of the master standard

(section 6.3.1 if the hot acid extraction wasused or section 6.3.2 if the ultrasonic extrac-tion procedure was used) to 100 ml with acidof the same concentration as used in pre-paring the master standard.

9.2 Calibration standards. Prepare daily bydiluting the working standard, with thesame acid matrix, as indicated below. Otherlead concentrations may be used.

Volume of 20 µg/ml working stand-ard, ml

Final vol-ume, ml

Concentra-tion µg Pb/

ml

0 ..................................................... 100 01.0 .................................................. 200 0.12.0 .................................................. 200 0.22.0 .................................................. 100 0.44.0 .................................................. 100 0.88.0 .................................................. 100 1.615.0 ................................................ 100 3.030.0 ................................................ 100 6.050.0 ................................................ 100 10.0100.0 .............................................. 100 20.0

9.3 Preparation of calibration curve. Sincethe working range of analysis will vary de-pending on which lead line is used and thetype of instrument, no one set of instruc-tions for preparation of a calibration curvecan be given. Select standards (plus the rea-gent blank), in the same acid concentrationas the samples, to cover the linear absorp-tion range indicated by the instrument man-ufacturer. Measure the absorbance of theblank and standards as in section 8.0. Repeatuntil good agreement is obtained betweenreplicates. Plot absorbance (y-axis) versusconcentration in µg Pb/ml (x-axis). Draw (orcompute) a straight line through the linearportion of the curve. Do not force the cali-bration curve through zero. Other calibra-tion procedures may be used.

To determine stability of the calibrationcurve, remeasure—alternately—one of thefollowing calibration standards for every10th sample analyzed: Concentration ≤ 1µgPb/ml; concentration ≤ 10 µg Pb/ml. If eitherstandard deviates by more than 5 percentfrom the value predicted by the calibrationcurve, recalibrate and repeat the previous 10analyses.

10. Calculation.10.1 Measured air volume. Calculate the

measured air volume at Standard Tempera-ture and Pressure as described in Reference10.

10.2 Lead concentration. Calculate lead con-centration in the air sample.


59


where:

C = Concentration, µg Pb/sm3.µg Pb/ml = Lead concentration determined

from section 8.100 ml/strip = Total sample volume.12 strips = Total useable filter area, 8″×9″. Ex-

posed area of one strip, 3⁄4″×7″.Filter = Total area of one strip, 3⁄4″×8″.Fb = Lead concentration of blank filter, µg,

from section 6.1.1.2.3.VSTP = Air volume from section 10.2.

11. Quality control.3⁄4″×8″ glass fiber filter strips containing 80

to 2000 µg Pb/strip (as lead salts) and blankstrips with zero Pb content should be used todetermine if the method—as being used—hasany bias. Quality control charts should beestablished to monitor differences betweenmeasured and true values. The frequency ofsuch checks will depend on the local qualitycontrol program.

To minimize the possibility of generatingunreliable data, the user should follow prac-tices established for assuring the quality ofair pollution data, (13) and take part inEPA’s semiannual audit program for leadanalyses.

12. Trouble shooting.1. During extraction of lead by the hot ex-

traction procedure, it is important to keepthe sample covered so that corrosion prod-ucts—formed on fume hood surfaces whichmay contain lead—are not deposited in theextract.

2. The sample acid concentration shouldminimize corrosion of the nebulizer. How-ever, different nebulizers may require loweracid concentrations. Lower concentrationscan be used provided samples and standardshave the same acid concentration.

3. Ashing of particulate samples has beenfound, by EPA and contractor laboratories,to be unnecessary in lead analyses by atomicabsorption. Therefore, this step was omittedfrom the method.

4. Filtration of extracted samples, to re-move particulate matter, was specifically ex-cluded from sample preparation, becausesome analysts have observed losses of leaddue to filtration.

5. If suspended solids should clog thenebulizer during analysis of samples, cen-trifuge the sample to remove the solids.

13. Authority.(Secs. 109 and 301(a), Clean Air Act, as

amended (42 U.S.C. 7409, 7601(a)))14. References.1. Scott, D. R. et al. ‘‘Atomic Absorption

and Optical Emission Analysis of NASN At-

mospheric Particulate Samples for Lead.’’Envir. Sci. and Tech., 10, 877–880 (1976).

2. Skogerboe, R. K. et al. ‘‘Monitoring forLead in the Environment.’’ pp. 57–66, Depart-ment of Chemistry, Colorado State Univer-sity, Fort Collins, CO 80523. Submitted toNational Science Foundation for publica-tions, 1976.

3. Zdrojewski, A. et al. ‘‘The AccurateMeasurement of Lead in Airborne Particu-lates.’’ Inter. J. Environ. Anal. Chem., 2, 63–77(1972).

4. Slavin, W., ‘‘Atomic Absorption Spec-troscopy.’’ Published by Interscience Com-pany, New York, NY (1968).

5. Kirkbright, G. F., and Sargent, M.,‘‘Atomic Absorption and Fluorescence Spec-troscopy.’’ Published by Academic Press,New York, NY 1974.

6. Burnham, C. D. et al., ‘‘Determination ofLead in Airborne Particulates in Chicagoand Cook County, IL, by Atomic AbsorptionSpectroscopy.’’ Envir. Sci. and Tech., 3, 472–475 (1969).

7. ‘‘Proposed Recommended Practices forAtomic Absorption Spectrometry.’’ ASTMBook of Standards, part 30, pp. 1596–1608 (July1973).

8. Koirttyohann, S. R. and Wen, J. W.,‘‘Critical Study of the APCD–MIBK Extrac-tion System for Atomic Absorption.’’ Anal.Chem., 45, 1986–1989 (1973).

9. Collaborative Study of Reference Methodfor the Determination of Suspended Particulatesin the Atmosphere (High Volume Method). Ob-tainable from National Technical Informa-tion Service, Department of Commerce, PortRoyal Road, Springfield, VA 22151, as PB–205–891.

10. [Reserved]11. Dubois, L., et al., ‘‘The Metal Content

of Urban Air.’’ JAPCA, 16, 77–78 (1966).12. EPA Report No. 600/4–77–034, June 1977,

‘‘Los Angeles Catalyst Study Symposium.’’Page 223.

13. Quality Assurance Handbook for Air Pol-lution Measurement System. Volume 1—Prin-ciples. EPA–600/9–76–005, March 1976.

14. Thompson, R. J. et al., ‘‘Analysis of Se-lected Elements in Atmospheric ParticulateMatter by Atomic Absorption.’’ Atomic Ab-sorption Newsletter, 9, No. 3, May-June 1970.

15. To be published. EPA, QAB, EMSL,RTP, N.C. 27711

16. Quality Assurance Handbook for Air Pol-lution Measurement Systems. Volume II—Ambi-ent Air Specific Methods. EPA–600/4–77/027a,May 1977.


60



61

Environmental Protection Agency Pt. 50, App. H

(Secs. 109, 301(a) of the Clean Air Act, as amended (42 U.S.C. 7409, 7601(a)); secs. 110, 301(a) and319 of the Clean Air Act (42 U.S.C. 7410, 7601(a), 7619))

[43 FR 46258, Oct. 5, 1978; 44 FR 37915, June 29, 1979, as amended at 46 FR 44163, Sept. 3, 1981;52 FR 24664, July 1, 1987]

APPENDIX H TO PART 50—INTERPRETA-TION OF THE 1-HOUR PRIMARY ANDSECONDARY NATIONAL AMBIENT AIRQUALITY STANDARDS FOR OZONE

1. GENERAL

This appendix explains how to determinewhen the expected number of days per cal-endar year with maximum hourly averageconcentrations above 0.12 ppm (235 µg/m3) isequal to or less than 1. An expanded discus-sion of these procedures and associated ex-

amples are contained in the ‘‘Guideline forInterpretation of Ozone Air Quality Stand-ards.’’ For purposes of clarity in the fol-lowing discussion, it is convenient to use theterm ‘‘exceedance’’ to describe a daily max-imum hourly average ozone measurementthat is greater than the level of the stand-ard. Therefore, the phrase ‘‘expected numberof days with maximum hourly average ozoneconcentrations above the level of the stand-ard’’ may be simply stated as the ‘‘expectednumber of exceedances.’’


62

40 CFR Ch. I (7–1–01 Edition)Pt. 50, App. H

The basic principle in making this deter-mination is relatively straightforward. Mostof the complications that arise in deter-mining the expected number of annualexceedances relate to accounting for incom-plete sampling. In general, the average num-ber of exceedances per calendar year must beless than or equal to 1. In its simplest form,the number of exceedances at a monitoringsite would be recorded for each calendar yearand then averaged over the past 3 calendaryears to determine if this average is lessthan or equal to 1.

2. INTERPRETATION OF EXPECTEDEXCEEDANCES

The ozone standard states that the ex-pected number of exceedances per year mustbe less than or equal to 1. The statisticalterm ‘‘expected number’’ is basically anarithmetic average. The following exampleexplains what it would mean for an area tobe in compliance with this type of standard.Suppose a monitoring station records a validdaily maximum hourly average ozone valuefor every day of the year during the past 3years. At the end of each year, the number ofdays with maximum hourly concentrationsabove 0.12 ppm is determined and this num-ber is averaged with the results of previousyears. As long as this average remains ‘‘lessthan or equal to 1,’’ the area is in compli-ance.

3. ESTIMATING THE NUMBER OF EXCEEDANCESFOR A YEAR

In general, a valid daily maximum hourlyaverage value may not be available for eachday of the year, and it will be necessary toaccount for these missing values when esti-mating the number of exceedances for a par-ticular calendar year. The purpose of thesecomputations is to determine if the expectednumber of exceedances per year is less thanor equal to 1. Thus, if a site has two or moreobserved exceedances each year, the stand-ard is not met and it is not necessary to usethe procedures of this section to account forincomplete sampling.

The term ‘‘missing value’’ is used here inthe general sense to describe all days that donot have an associated ozone measurement.In some cases, a measurement might actu-ally have been missed but in other cases nomeasurement may have been scheduled forthat day. A daily maximum ozone value isdefined to be the highest hourly ozone valuerecorded for the day. This daily maximumvalue is considered to be valid if 75 percent ofthe hours from 9:01 a.m. to 9:00 p.m. (LST)were measured or if the highest hour isgreater than the level of the standard.

In some areas, the seasonal pattern ofozone is so pronounced that entire monthsneed not be sampled because it is extremelyunlikely that the standard would be exceed-

ed. Any such waiver of the ozone monitoringrequirement would be handled under provi-sions of 40 CFR, part 58. Some allowanceshould also be made for days for which validdaily maximum hourly values were not ob-tained but which would quite likely havebeen below the standard. Such an allowanceintroduces a complication in that it becomesnecessary to define under what conditions amissing value may be assumed to have beenless than the level of the standard. The fol-lowing criterion may be used for ozone:

A missing daily maximum ozone valuemay be assumed to be less than the level ofthe standard if the valid daily maxima onboth the preceding day and the following daydo not exceed 75 percent of the level of thestandard.

Let z denote the number of missing dailymaximum values that may be assumed to beless than the standard. Then the followingformula shall be used to estimate the ex-pected number of exceedances for the year:

e v v n N= +[( / ) (8 -n-z)] (1)(*Indicates multiplication.)

where:

e = the estimated number of exceedances forthe year,

N = the number of required monitoring daysin the year,

n = the number of valid daily maxima,v = the number of daily values above the

level of the standard, andz = the number of days assumed to be less

than the standard level.

This estimated number of exceedancesshall be rounded to one decimal place (frac-tional parts equal to 0.05 round up).

It should be noted that N will be the totalnumber of days in the year unless the appro-priate Regional Administrator has granted awaiver under the provisions of 40 CFR part58.

The above equation may be interpreted in-tuitively in the following manner. The esti-mated number of exceedances is equal to theobserved number of exceedances (v) plus anincrement that accounts for incomplete sam-pling. There were (N-n) missing values forthe year but a certain number of these,namely z, were assumed to be less than thestandard. Therefore, (N-n-z) missing valuesare considered to include possibleexceedances. The fraction of measured val-ues that are above the level of the standardis v/n. It is assumed that this same fractionapplies to the (N-n-z) missing values andthat (v/n)*(N-n-z) of these values would alsohave exceeded the level of the standard.

[44 FR 8220, Feb. 8, 1979, as amended at 62 FR38895, July 18, 1997]


63

Environmental Protection Agency Pt. 50, App. I

APPENDIX I TO PART 50—INTERPRETA-TION OF THE 8-HOUR PRIMARY ANDSECONDARY NATIONAL AMBIENT AIRQUALITY STANDARDS FOR OZONE

1. General.This appendix explains the data handling

conventions and computations necessary fordetermining whether the national 8-hour pri-mary and secondary ambient air qualitystandards for ozone specified in § 50.10 aremet at an ambient ozone air quality moni-toring site. Ozone is measured in the ambi-ent air by a reference method based on ap-pendix D of this part. Data reporting, datahandling, and computation procedures to beused in making comparisons between re-ported ozone concentrations and the level ofthe ozone standard are specified in the fol-lowing sections. Whether to exclude, retain,or make adjustments to the data affected bystratospheric ozone intrusion or other nat-ural events is subject to the approval of theappropriate Regional Administrator.

2. Primary and Secondary Ambient Air Qual-ity Standards for Ozone.

2.1 Data Reporting and Handling Conven-tions.

2.1.1 Computing 8-hour averages. Hourly av-erage concentrations shall be reported inparts per million (ppm) to the third decimalplace, with additional digits to the rightbeing truncated. Running 8-hour averagesshall be computed from the hourly ozoneconcentration data for each hour of the yearand the result shall be stored in the first, orstart, hour of the 8-hour period. An 8-houraverage shall be considered valid if at least75% of the hourly averages for the 8-hour pe-riod are available. In the event that only 6(or 7) hourly averages are available, the 8-hour average shall be computed on the basisof the hours available using 6 (or 7) as the di-visor. (8-hour periods with three or moremissing hours shall not be ignored if, aftersubstituting one-half the minimum detect-able limit for the missing hourly concentra-tions, the 8-hour average concentration isgreater than the level of the standard.) Thecomputed 8-hour average ozone concentra-tions shall be reported to three decimalplaces (the insignificant digits to the right ofthe third decimal place are truncated, con-sistent with the data handling procedures forthe reported data.)

2.1.2 Daily maximum 8-hour average con-centrations. (a) There are 24 possible running8-hour average ozone concentrations for eachcalendar day during the ozone monitoringseason. (Ozone monitoring seasons vary bygeographic location as designated in part 58,appendix D to this chapter.) The daily max-imum 8-hour concentration for a given cal-endar day is the highest of the 24 possible 8-hour average concentrations computed forthat day. This process is repeated, yielding adaily maximum 8-hour average ozone con-

centration for each calendar day with ambi-ent ozone monitoring data. Because the 8-hour averages are recorded in the start hour,the daily maximum 8-hour concentrationsfrom two consecutive days may have somehourly concentrations in common. Gen-erally, overlapping daily maximum 8-houraverages are not likely, except in those non-urban monitoring locations with less pro-nounced diurnal variation in hourly con-centrations.

(b) An ozone monitoring day shall becounted as a valid day if valid 8-hour aver-ages are available for at least 75% of possiblehours in the day (i.e., at least 18 of the 24averages). In the event that less than 75% ofthe 8-hour averages are available, a day shallalso be counted as a valid day if the dailymaximum 8-hour average concentration forthat day is greater than the level of the am-bient standard.

2.2 Primary and Secondary Standard-relatedSummary Statistic. The standard-related sum-mary statistic is the annual fourth-highestdaily maximum 8-hour ozone concentration,expressed in parts per million, averaged overthree years. The 3-year average shall be com-puted using the three most recent, consecu-tive calendar years of monitoring data meet-ing the data completeness requirements de-scribed in this appendix. The computed 3-year average of the annual fourth-highestdaily maximum 8-hour average ozone con-centrations shall be expressed to three dec-imal places (the remaining digits to theright are truncated.)

2.3 Comparisons with the Primary and Sec-ondary Ozone Standards. (a) The primary andsecondary ozone ambient air quality stand-ards are met at an ambient air quality moni-toring site when the 3-year average of theannual fourth-highest daily maximum 8-houraverage ozone concentration is less than orequal to 0.08 ppm. The number of significantfigures in the level of the standard dictatesthe rounding convention for comparing thecomputed 3-year average annual fourth-high-est daily maximum 8-hour average ozoneconcentration with the level of the standard.The third decimal place of the computedvalue is rounded, with values equal to orgreater than 5 rounding up. Thus, a com-puted 3-year average ozone concentration of0.085 ppm is the smallest value that is great-er than 0.08 ppm.

(b) This comparison shall be based on threeconsecutive, complete calendar years of airquality monitoring data. This requirement ismet for the three year period at a moni-toring site if daily maximum 8-hour averageconcentrations are available for at least 90%,on average, of the days during the designatedozone monitoring season, with a minimumdata completeness in any one year of at least75% of the designated sampling days. When


64

40 CFR Ch. I (7–1–01 Edition)Pt. 50, App. J

computing whether the minimum data com-pleteness requirements have been met, mete-orological or ambient data may be sufficientto demonstrate that meteorological condi-tions on missing days were not conducive toconcentrations above the level of the stand-ard. Missing days assumed less than the levelof the standard are counted for the purposeof meeting the data completeness require-ment, subject to the approval of the appro-priate Regional Administrator.

(c) Years with concentrations greater thanthe level of the standard shall not be ignoredon the ground that they have less than com-plete data. Thus, in computing the 3-year av-erage fourth maximum concentration, cal-endar years with less than 75% data com-pleteness shall be included in the computa-

tion if the average annual fourth maximum8-hour concentration is greater than thelevel of the standard.

(d) Comparisons with the primary and sec-ondary ozone standards are demonstrated byexamples 1 and 2 in paragraphs (d)(1) and (d)(2) respectively as follows:

(1) As shown in example 1, the primary andsecondary standards are met at this moni-toring site because the 3-year average of theannual fourth-highest daily maximum 8-houraverage ozone concentrations (i.e., 0.084 ppm)is less than or equal to 0.08 ppm. The datacompleteness requirement is also met be-cause the average percent of days with validambient monitoring data is greater than90%, and no single year has less than 75%data completeness.

EXAMPLE 1. AMBIENT MONITORING SITE ATTAINING THE PRIMARY AND SECONDARY OZONE STANDARDS

Year PercentValid Days

1st HighestDaily Max

8-hourConc. (ppm)

2nd HighestDaily Max

8-hourConc. (ppm)

3rd HighestDaily Max

8-hourConc. (ppm)

4th HighestDaily Max

8-hourConc. (ppm)


8-hourConc. (ppm)

1993 ...................................................... 100% 0.092 0.091 0.090 0.088 0.085

1994 ...................................................... 96% 0.090 0.089 0.086 0.084 0.080

1995 ...................................................... 98% 0.087 0.085 0.083 0.080 0.075

Average .......................................... 98%

(2) As shown in example 2, the primary andsecondary standards are not met at thismonitoring site because the 3-year averageof the fourth-highest daily maximum 8-houraverage ozone concentrations (i.e., 0.093 ppm)is greater than 0.08 ppm. Note that the ozone

concentration data for 1994 is used in thesecomputations, even though the data captureis less than 75%, because the average fourth-highest daily maximum 8-hour average con-centration is greater than 0.08 ppm.

EXAMPLE 2. AMBIENT MONITORING SITE FAILING TO MEET THE PRIMARY AND SECONDARY OZONESTANDARDS

Year PercentValid Days

1st HighestDaily Max

8-hourConc. (ppm)

2nd HighestDaily Max

8-hourConc. (ppm)

3rd HighestDaily Max

8-hourConc. (ppm)


8-hourConc. (ppm)


8-hourConc. (ppm)

1993 ...................................................... 96% 0.105 0.103 0.103 0.102 0.102

1994 ...................................................... 74% 0.090 0.085 0.082 0.080 0.078

1995 ...................................................... 98% 0.103 0.101 0.101 0.097 0.095

Average .......................................... 89%

3. Design Values for Primary and SecondaryAmbient Air Quality Standards for Ozone. Theair quality design value at a monitoring siteis defined as that concentration that whenreduced to the level of the standard ensuresthat the site meets the standard. For a con-centration-based standard, the air qualitydesign value is simply the standard-relatedtest statistic. Thus, for the primary and sec-ondary ozone standards, the 3-year averageannual fourth-highest daily maximum 8-hour

average ozone concentration is also the airquality design value for the site.

[62 FR 38895, July 18, 1997]

APPENDIX J TO PART 50—REFERENCEMETHOD FOR THE DETERMINATION OFPARTICULATE MATTER AS PM10 INTHE ATMOSPHERE

1.0 Applicability.


65

Environmental Protection Agency Pt. 50, App. J

1.1 This method provides for the measure-ment of the mass concentration of particu-late matter with an aerodynamic diameterless than or equal to a nominal 10 microm-eters (PM1O) in ambient air over a 24-hourperiod for purposes of determining attain-ment and maintenance of the primary andsecondary national ambient air qualitystandards for particulate matter specified in§ 50.6 of this chapter. The measurement proc-ess is nondestructive, and the PM10 samplecan be subjected to subsequent physical orchemical analyses. Quality assurance proce-dures and guidance are provided in part 58,appendices A and B, of this chapter and inReferences 1 and 2.

2.0 Principle.2.1 An air sampler draws ambient air at a

constant flow rate into a specially shapedinlet where the suspended particulate matteris inertially separated into one or more sizefractions within the PM10 size range. Eachsize fraction in the PM1O size range is thencollected on a separate filter over the speci-fied sampling period. The particle size dis-crimination characteristics (sampling effec-tiveness and 50 percent cutpoint) of the sam-pler inlet are prescribed as performancespecifications in part 53 of this chapter.

2.2 Each filter is weighed (after moistureequilibration) before and after use to deter-mine the net weight (mass) gain due to col-lected PM10. The total volume of air sampled,corrected to EPA reference conditions (25 C,101.3 kPa), is determined from the measuredflow rate and the sampling time. The massconcentration of PM10 in the ambient air iscomputed as the total mass of collected par-ticles in the PM10 size range divided by thevolume of air sampled, and is expressed inmicrograms per standard cubic meter (µg/stdm3). For PM10 samples collected at tempera-tures and pressures significantly differentfrom EPA reference conditions, these cor-rected concentrations sometimes differ sub-stantially from actual concentrations (inmicrograms per actual cubic meter), particu-larly at high elevations. Although not re-quired, the actual PM10 concentration can becalculated from the corrected concentration,using the average ambient temperature andbarometric pressure during the sampling pe-riod.

2.3 A method based on this principle will beconsidered a reference method only if (a) theassociated sampler meets the requirementsspecified in this appendix and the require-ments in part 53 of this chapter, and (b) themethod has been designated as a referencemethod in accordance with part 53 of thischapter.

3.0 Range.3.1 The lower limit of the mass concentra-

tion range is determined by the repeatabilityof filter tare weights, assuming the nominalair sample volume for the sampler. For sam-plers having an automatic filter-changing

mechanism, there may be no upper limit.For samplers that do not have an automaticfilter-changing mechanism, the upper limitis determined by the filter mass loading be-yond which the sampler no longer maintainsthe operating flow rate within specified lim-its due to increased pressure drop across theloaded filter. This upper limit cannot bespecified precisely because it is a complexfunction of the ambient particle size dis-tribution and type, humidity, filter type, andperhaps other factors. Nevertheless, all sam-plers should be capable of measuring 24-hourPM10 mass concentrations of at least 300 µg/std m3 while maintaining the operating flowrate within the specified limits.

4.0 Precision.4.1 The precision of PM10 samplers must be

5 µg/m3 for PM10 concentrations below 80 µg/m3 and 7 percent for PM10 concentrationsabove 80 µg/m3, as required by part 53 of thischapter, which prescribes a test procedurethat determines the variation in the PM10

concentration measurements of identicalsamplers under typical sampling conditions.Continual assessment of precision via collo-cated samplers is required by part 58 of thischapter for PM10 samplers used in certainmonitoring networks.

5.0 Accuracy.5.1 Because the size of the particles making

up ambient particulate matter varies over awide range and the concentration of par-ticles varies with particle size, it is difficultto define the absolute accuracy of PM10 sam-plers. Part 53 of this chapter provides a spec-ification for the sampling effectiveness ofPM10 samplers. This specification requiresthat the expected mass concentration cal-culated for a candidate PM10 sampler, whensampling a specified particle size distribu-tion, be within ±10 percent of that calculatedfor an ideal sampler whose sampling effec-tiveness is explicitly specified. Also, the par-ticle size for 50 percent samplingeffectivensss is required to be 10±0.5 microm-eters. Other specifications related to accu-racy apply to flow measurement and calibra-tion, filter media, analytical (weighing) pro-cedures, and artifact. The flow rate accuracyof PM10 samplers used in certain monitoringnetworks is required by part 58 of this chap-ter to be assessed periodically via flow rateaudits.

6.0 Potential Sources of Error.6.1 Volatile Particles. Volatile particles col-

lected on filters are often lost during ship-ment and/or storage of the filters prior tothe post-sampling weighing 3. Although ship-ment or storage of loaded filters is some-times unavoidable, filters should be re-weighed as soon as practical to minimizethese losses.

6.2 Artifacts. Positive errors in PM10 con-centration measurements may result fromretention of gaseous species on filters 4, 5.

Such errors include the retention of sulfur


66


dioxide and nitric acid. Retention of sulfurdioxide on filters, followed by oxidation tosulfate, is referred to as artifact sulfate for-mation, a phenomenon which increases withincreasing filter alkalinity 6. Little or no ar-tifact sulfate formation should occur usingfilters that meet the alkalinity specificationin section 7.2.4. Artifact nitrate formation,resulting primarily from retention of nitricacid, occurs to varying degrees on many fil-ter types, including glass fiber, celluloseester, and many quartz fiber filters 5, 7, 8, 9, 10.

Loss of true atmospheric particulate nitrateduring or following sampling may also occurdue to dissociation or chemical reaction.This phenomenon has been observed on Tef-lon filters 8 and inferred for quartz fiber fil-ters 11, 12. The magnitude of nitrate artifacterrors in PM10 mass concentration measure-ments will vary with location and ambienttemperature; however, for most sampling lo-cations, these errors are expected to besmall.

6.3 Humidity. The effects of ambient humid-ity on the sample are unavoidable. The filterequilibration procedure in section 9.0 is de-signed to minimize the effects of moisture onthe filter medium.

6.4 Filter Handling. Careful handling of fil-ters between presampling and postsamplingweighings is necessary to avoid errors due todamaged filters or loss of collected particlesfrom the filters. Use of a filter cartridge orcassette may reduce the magnitude of theseerrors. Filters must also meet the integrityspecification in section 7.2.3.

6.5 Flow Rate Variation. Variations in thesampler’s operating flow rate may alter theparticle size discrimination characteristicsof the sampler inlet. The magnitude of thiserror will depend on the sensitivity of theinlet to variations in flow rate and on theparticle distribution in the atmosphere dur-ing the sampling period. The use of a flowcontrol device (section 7.1.3) is required tominimize this error.

6.6 Air Volume Determination. Errors in theair volume determination may result fromerrors in the flow rate and/or sampling timemeasurements. The flow control deviceserves to minimize errors in the flow rate de-termination, and an elapsed time meter (sec-tion 7.1.5) is required to minimize the errorin the sampling time measurement.

7.0 Apparatus.7.1 PM10 Sampler.7.1.1 The sampler shall be designed to:a. Draw the air sample into the sampler

inlet and through the particle collection fil-ter at a uniform face velocity.

b. Hold and seal the filter in a horizontalposition so that sample air is drawn down-ward through the filter.

c. Allow the filter to be installed and re-moved conveniently.

d. Protect the filter and sampler from pre-cipitation and prevent insects and other de-bris from being sampled.

e. Minimize air leaks that would causeerror in the measurement of the air volumepassing through the filter.

f. Discharge exhaust air at a sufficient dis-tance from the sampler inlet to minimize thesampling of exhaust air.

g. Minimize the collection of dust from thesupporting surface.

7.1.2 The sampler shall have a sample airinlet system that, when operated within aspecified flow rate range, provides particlesize discrimination characteristics meetingall of the applicable performance specifica-tions prescribed in part 53 of this chapter.The sampler inlet shall show no significantwind direction dependence. The latter re-quirement can generally be satisfied by aninlet shape that is circularly symmetricalabout a vertical axis.

7.1.3 The sampler shall have a flow controldevice capable of maintaining the sampler’soperating flow rate within the flow rate lim-its specified for the sampler inlet over nor-mal variations in line voltage and filter pres-sure drop.

7.1.4 The sampler shall provide a means tomeasure the total flow rate during the sam-pling period. A continuous flow recorder isrecommended but not required. The flowmeasurement device shall be accurate to ±2percent.

7.1.5 A timing/control device capable ofstarting and stopping the sampler shall beused to obtain a sample collection period of24 ±1 hr (1,440 ±60 min). An elapsed timemeter, accurate to within ±15 minutes, shallbe used to measure sampling time. Thismeter is optional for samplers with contin-uous flow recorders if the sampling timemeasurement obtained by means of the re-corder meets the ±15 minute accuracy speci-fication.

7.1.6 The sampler shall have an associatedoperation or instruction manual as requiredby part 53 of this chapter which includes de-tailed instructions on the calibration, oper-ation, and maintenance of the sampler.

7.2 Filters.7.2.1 Filter Medium. No commercially avail-

able filter medium is ideal in all respects forall samplers. The user’s goals in sampling de-termine the relative importance of variousfilter characteristics (e.g., cost, ease of han-dling, physical and chemical characteristics,etc.) and, consequently, determine thechoice among acceptable filters. Further-more, certain types of filters may not besuitable for use with some samplers, particu-larly under heavy loading conditions (highmass concentrations), because of high orrapid increase in the filter flow resistancethat would exceed the capability of the sam-pler’s flow control device. However, samplersequipped with automatic filter-changing


67

Environmental Protection Agency Pt. 50, App. J

mechanisms may allow use of these types offilters. The specifications given below areminimum requirements to ensure accept-ability of the filter medium for measurementof PM10 mass concentrations. Other filterevaluation criteria should be considered tomeet individual sampling and analysis objec-tives.

7.2.2 Collection Efficiency. ´99 percent, asmeasured by the DOP test (ASTM–2986) with0.3 µm particles at the sampler’s operatingface velocity.

7.2.3 Integrity. ±5 µg/m3 (assuming sampler’snominal 24-hour air sample volume). Integ-rity is measured as the PM10 concentrationequivalent corresponding to the average dif-ference between the initial and the finalweights of a random sample of test filtersthat are weighed and handled under actualor simulated sampling conditions, but haveno air sample passed through them (i.e., fil-ter blanks). As a minimum, the test proce-dure must include initial equilibration andweighing, installation on an inoperativesampler, removal from the sampler, and finalequilibration and weighing.

7.2.4 Alkalinity. <25 microequivalents/gramof filter, as measured by the procedure givenin Reference 13 following at least twomonths storage in a clean environment (freefrom contamination by acidic gases) at roomtemperature and humidity.

7.3 Flow Rate Transfer Standard. The flowrate transfer standard must be suitable forthe sampler’s operating flow rate and mustbe calibrated against a primary flow or vol-ume standard that is traceable to the Na-tional Bureau of Standards (NBS). The flowrate transfer standard must be capable ofmeasuring the sampler’s operating flow ratewith an accuracy of ±2 percent.

7.4 Filter Conditioning Environment.7.4.1 Temperature range: 15 to 30 C.7.4.2 Temperature control: ±3 C.7.4.3 Humidity range: 20% to 45% RH.7.4.4 Humidity control: ±5% RH.7.5 Analytical Balance. The analytical bal-

ance must be suitable for weighing the typeand size of filters required by the sampler.The range and sensitivity required will de-pend on the filter tare weights and massloadings. Typically, an analytical balancewith a sensitivity of 0.1 mg is required forhigh volume samplers (flow rates >0.5 m3/min). Lower volume samplers (flow rates <0.5m3/min) will require a more sensitive bal-ance.

8.0 Calibration.8.1 General Requirements.8.1.1 Calibration of the sampler’s flow

measurement device is required to establishtraceability of subsequent flow measure-ments to a primary standard. A flow ratetransfer standard calibrated against a pri-mary flow or volume standard shall be usedto calibrate or verify the accuracy of thesampler’s flow measurement device.

8.1.2 Particle size discrimination by iner-tial separation requires that specific air ve-locities be maintained in the sampler’s airinlet system. Therefore, the flow ratethrough the sampler’s inlet must be main-tained throughout the sampling period with-in the design flow rate range specified by themanufacturer. Design flow rates are speci-fied as actual volumetric flow rates, meas-ured at existing conditions of temperatureand pressure (Qa). In contrast, mass con-centrations of PM10 are computed using flowrates corrected to EPA reference conditionsof temperature and pressure (Qstd).

8.2 Flow Rate Calibration Procedure.8.2.1 PM10 samplers employ various types

of flow control and flow measurement de-vices. The specific procedure used for flowrate calibration or verification will vary de-pending on the type of flow controller andflow indicator employed. Calibration interms of actual volumetric flow rates (Qa) isgenerally recommended, but other measuresof flow rate (e.g., Qstd) may be used providedthe requirements of section 8.1 are met. Thegeneral procedure given here is based on ac-tual volumetric flow units (Qa) and serves toillustrate the steps involved in the calibra-tion of a PM10 sampler. Consult the samplermanufacturer’s instruction manual and Ref-erence 2 for specific guidance on calibration.Reference 14 provides additional informationon the use of the commonly used measures offlow rate and their interrelationships.

8.2.2 Calibrate the flow rate transfer stand-ard against a primary flow or volume stand-ard traceable to NBS. Establish a calibrationrelationship (e.g., an equation or family ofcurves) such that traceability to the primarystandard is accurate to within 2 percent overthe expected range of ambient conditions(i.e., temperatures and pressures) underwhich the transfer standard will be used. Re-calibrate the transfer standard periodically.

8.2.3 Following the sampler manufacturer’sinstruction manual, remove the samplerinlet and connect the flow rate transferstandard to the sampler such that the trans-fer standard accurately measures the sam-pler’s flow rate. Make sure there are no leaksbetween the transfer standard and the sam-pler.

8.2.4 Choose a minimum of three flow rates(actual m3/min), spaced over the acceptableflow rate range specified for the inlet (see7.1.2) that can be obtained by suitable adjust-ment of the sampler flow rate. In accordancewith the sampler manufacturer’s instructionmanual, obtain or verify the calibration re-lationship between the flow rate (actual m3/min) as indicated by the transfer standardand the sampler’s flow indicator response.Record the ambient temperature and baro-metric pressure. Temperature and pressurecorrections to subsequent flow indicatorreadings may be required for certain types of


68


flow measurement devices. When such cor-rections are necessary, correction on an indi-vidual or daily basis is preferable. However,seasonal average temperature and averagebarometric pressure for the sampling sitemay be incorporated into the sampler cali-bration to avoid daily corrections. Consultthe sampler manufacturer’s instruction man-ual and Reference 2 for additional guidance.

8.2.5 Following calibration, verify that thesampler is operating at its design flow rate(actual m3/min) with a clean filter in place.

8.2.6 Replace the sampler inlet.9.0 Procedure.9.1 The sampler shall be operated in ac-

cordance with the specific guidance providedin the sampler manufacturer’s instructionmanual and in Reference 2. The general pro-cedure given here assumes that the sampler’sflow rate calibration is based on flow ratesat ambient conditions (Qa) and serves to il-lustrate the steps involved in the operationof a PM10 sampler.

9.2 Inspect each filter for pinholes, par-ticles, and other imperfections. Establish afilter information record and assign an iden-tification number to each filter.

9.3 Equilibrate each filter in the condi-tioning environment (see 7.4) for at least 24hours.

9.4 Following equilibration, weigh each fil-ter and record the presampling weight withthe filter identification number.

9.5 Install a preweighed filter in the sam-pler following the instructions provided inthe sampler manufacturer’s instruction man-ual.

9.6 Turn on the sampler and allow it to es-tablish run-temperature conditions. Recordthe flow indicator reading and, if needed, theambient temperature and barometric pres-sure. Determine the sampler flow rate (ac-tual m3/min) in accordance with the instruc-tions provided in the sampler manufacturer’sinstruction manual. NOTE.—No onsite tem-perature or pressure measurements are nec-essary if the sampler’s flow indicator doesnot require temperature or pressure correc-tions or if seasonal average temperature andaverage barometric pressure for the sam-pling site are incorporated into the samplercalibration (see step 8.2.4). If individual ordaily temperature and pressure correctionsare required, ambient temperature and baro-metric pressure can be obtained by on-sitemeasurements or from a nearby weather sta-tion. Barometric pressure readings obtainedfrom airports must be station pressure, notcorrected to sea level, and may need to becorrected for differences in elevation be-tween the sampling site and the airport.

9.7 If the flow rate is outside the accept-able range specified by the manufacturer,check for leaks, and if necessary, adjust theflow rate to the specified setpoint. Stop thesampler.

9.8 Set the timer to start and stop the sam-pler at appropriate times. Set the elapsedtime meter to zero or record the initialmeter reading.

9.9 Record the sample information (site lo-cation or identification number, sampledate, filter identification number, and sam-pler model and serial number).

9.10 Sample for 24±1 hours.9.11 Determine and record the average flow

rate (Q̄a) in actual m3/min for the samplingperiod in accordance with the instructionsprovided in the sampler manufacturer’s in-struction manual. Record the elapsed timemeter final reading and, if needed, the aver-age ambient temperature and barometricpressure for the sampling period (see notefollowing step 9.6).

9.12 Carefully remove the filter from thesampler, following the sampler manufactur-er’s instruction manual. Touch only theouter edges of the filter.

9.13 Place the filter in a protective holderor container (e.g., petri dish, glassine enve-lope, or manila folder).

9.14 Record any factors such as meteoro-logical conditions, construction activity,fires or dust storms, etc., that might be per-tinent to the measurement on the filter in-formation record.

9.15 Transport the exposed sample filter tothe filter conditioning environment as soonas possible for equilibration and subsequentweighing.

9.16 Equilibrate the exposed filter in theconditioning environment for at least 24hours under the same temperature and hu-midity conditions used for presampling filterequilibration (see 9.3).

9.17 Immediately after equilibration, re-weigh the filter and record the postsamplingweight with the filter identification number.

10.0 Sampler Maintenance.10.1 The PM10 sampler shall be maintained

in strict accordance with the maintenanceprocedures specified in the sampler manufac-turer’s instruction manual.

11.0 Calculations.11.1 Calculate the average flow rate over

the sampling period corrected to EPA ref-erence conditions as Q̄std. When the sampler’sflow indicator is calibrated in actual volu-metric units (Qa), Q̄std is calculated as:

Q̄std=Q̄a×(Pav/Tav)(Tstd/Pstd)

where

Q̄std = average flow rate at EPA referenceconditions, std m3/min;

Q̄a = average flow rate at ambient conditions,m3/min;

Pav = average barometric pressure during thesampling period or average barometricpressure for the sampling site, kPa (or mmHg);

Tav = average ambient temperature duringthe sampling period or seasonal average


69

Environmental Protection Agency Pt. 50, App. K

ambient temperature for the sampling site,K;

Tstd = standard temperature, defined as 298 K;Pstd = standard pressure, defined as 101.3 kPa

(or 760 mm Hg).

11.2 Calculate the total volume of air sam-pled as:

Vstd = Q̄std×t

where

Vstd = total air sampled in standard volumeunits, std m3;

t = sampling time, min.

11.3 Calculate the PM10 concentration as:

PM10 = (Wf¥Wi)×106/Vstd

where

PM10 = mass concentration of PM10, µg/stdm3;

Wf, Wi = final and initial weights of filter col-lecting PM1O particles, g;

106 = conversion of g to µg.

NOTE: If more than one size fraction in thePM10 size range is collected by the sampler,the sum of the net weight gain by each col-lection filter [Σ(Wf¥Wi)] is used to calculatethe PM10 mass concentration.


lution Measurement Systems, Volume I,Principles. EPA–600/9–76–005, March 1976.Available from CERI, ORD Publications,U.S. Environmental Protection Agency, 26West St. Clair Street, Cincinnati, OH 45268.

2. Quality Assurance Handbook for Air Pol-lution Measurement Systems, Volume II,Ambient Air Specific Methods. EPA–600/4–77–027a, May 1977. Available from CERI, ORDPublications, U.S. Environmental ProtectionAgency, 26 West St. Clair Street, Cincinnati,OH 45268.

3. Clement, R.E., and F.W. Karasek. Sam-ple Composition Changes in Sampling andAnalysis of Organic Compounds in Aerosols.Int. J. Environ. Analyt. Chem., 7:109, 1979.

4. Lee, R.E., Jr., and J. Wagman. A Sam-pling Anomaly in the Determination of At-mospheric Sulfate Concentration. Amer. Ind.Hyg. Assoc. J., 27:266, 1966.

5. Appel, B.R., S.M. Wall, Y. Tokiwa, andM. Haik. Interference Effects in SamplingParticulate Nitrate in Ambient Air. Atmos.Environ., 13:319, 1979.

6. Coutant, R.W. Effect of EnvironmentalVariables on Collection of Atmospheric Sul-fate. Environ. Sci. Technol., 11:873, 1977.

7. Spicer, C.W., and P. Schumacher. Inter-ference in Sampling Atmospheric Particu-late Nitrate. Atmos. Environ., 11:873, 1977.

8. Appel, B.R., Y. Tokiwa, and M. Haik.Sampling of Nitrates in Ambient Air. Atmos.Environ., 15:283, 1981.

9. Spicer, C.W., and P.M. Schumacher. Par-ticulate Nitrate: Laboratory and Field Stud-

ies of Major Sampling Interferences. Atmos.Environ., 13:543, 1979.

10. Appel, B.R. Letter to Larry Purdue,U.S. EPA, Environmental Monitoring andSupport Laboratory. March 18, 1982, DocketNo. A–82–37, II–I–1.

11. Pierson, W.R., W.W. Brachaczek, T.J.Korniski, T.J. Truex, and J.W. Butler. Arti-fact Formation of Sulfate, Nitrate, and Hy-drogen Ion on Backup Filters: AlleghenyMountain Experiment. J. Air Pollut. ControlAssoc., 30:30, 1980.

12. Dunwoody, C.L. Rapid Nitrate LossFrom PM10 Filters. J. Air Pollut. ControlAssoc., 36:817, 1986.

13. Harrell, R.M. Measuring the Alkalinityof Hi-Vol Air Filters. EMSL/RTP–SOP–QAD–534, October 1985. Available from the U.S. En-vironmental Protection Agency, EMSL/QAD,Research Triangle Park, NC 27711.

14. Smith, F., P.S. Wohlschlegel, R.S.C.Rogers, and D.J. Mulligan. Investigation ofFlow Rate Calibration Procedures Associ-ated With the High Volume Method for De-termination of Suspended Particulates.EPA–600/4–78–047, U.S. Environmental Pro-tection Agency, Research Triangle Park, NC27711, 1978.

[52 FR 24664, July 1, 1987; 52 FR 29467, Aug. 7,1987]

APPENDIX K TO PART 50—INTERPRETA-TION OF THE NATIONAL AMBIENT AIRQUALITY STANDARDS FOR PARTICU-LATE MATTER

1.0 General.(a) This appendix explains the computa-

tions necessary for analyzing particulatematter data to determine attainment of the24-hour and annual standards specified in 40CFR 50.6. For the primary and secondarystandards, particulate matter is measured inthe ambient air as PM10 (particles with anaerodynamic diameter less than or equal toa nominal 10 micrometers) by a referencemethod based on appendix J of this part anddesignated in accordance with part 53 of thischapter, or by an equivalent method des-ignated in accordance with part 53 of thischapter. The required frequency of measure-ments is specified in part 58 of this chapter.

(b) The terms used in this appendix are de-fined as follows:

Average refers to an arithmetic mean. Allparticulate matter standards are expressedin terms of expected annual values: Expectednumber of exceedances per year for the 24-hour standards and expected annual arith-metic mean for the annual standards.

Daily value for PM10 refers to the 24-houraverage concentration of PM10 calculated ormeasured from midnight to midnight (localtime).

Exceedance means a daily value that isabove the level of the 24-hour standard after


70

40 CFR Ch. I (7–1–01 Edition)Pt. 50, App. K

rounding to the nearest 10 µg/m3 (i.e., valuesending in 5 or greater are to be rounded up).

Expected annual value is the number ap-proached when the annual values from an in-creasing number of years are averaged, inthe absence of long-term trends in emissionsor meteorological conditions.

Year refers to a calendar year.(c) Although the discussion in this appen-

dix focuses on monitored data, the sameprinciples apply to modeling data, subject toEPA modeling guidelines.

2.0 Attainment Determinations.2.1 24-Hour Primary and Secondary Stand-

ards.(a) Under 40 CFR 50.6(a) the 24-hour pri-

mary and secondary standards are attainedwhen the expected number of exceedancesper year at each monitoring site is less thanor equal to one. In the simplest case, thenumber of expected exceedances at a site isdetermined by recording the number ofexceedances in each calendar year and thenaveraging them over the past 3 calendaryears. Situations in which 3 years of data arenot available and possible adjustments forunusual events or trends are discussed insections 2.3 and 2.4 of this appendix. Further,when data for a year are incomplete, it isnecessary to compute an estimated numberof exceedances for that year by adjusting theobserved number of exceedances. This proce-dure, performed by calendar quarter, is de-scribed in section 3.0 of this appendix. Theexpected number of exceedances is then esti-mated by averaging the individual annual es-timates for the past 3 years.

(b) The comparison with the allowable ex-pected exceedance rate of one per year ismade in terms of a number rounded to thenearest tenth (fractional values equal to orgreater than 0.05 are to be rounded up; e.g.,an exceedance rate of 1.05 would be roundedto 1.1, which is the lowest rate for nonattain-ment).

2.2 Annual Primary and Secondary Stand-ards. Under 40 CFR 50.6(b), the annual pri-mary and secondary standards are attainedwhen the expected annual arithmetic meanPM10 concentration is less than or equal tothe level of the standard. In the simplestcase, the expected annual arithmetic mean isdetermined by averaging the annual arith-metic mean PM10 concentrations for the past3 calendar years. Because of the potential forincomplete data and the possible seasonalityin PM10 concentrations, the annual meanshall be calculated by averaging the fourquarterly means of PM10 concentrationswithin the calendar year. The equations forcalculating the annual arithmetic mean aregiven in section 4.0 of this appendix. Situa-tions in which 3 years of data are not avail-able and possible adjustments for unusualevents or trends are discussed in sections 2.3and 2.4 of this appendix. The expected annualarithmetic mean is rounded to the nearest 1

µg/m3 before comparison with the annualstandards (fractional values equal to orgreater than 0.5 are to be rounded up).

2.3 Data Requirements.(a) 40 CFR 58.13 specifies the required min-

imum frequency of sampling for PM10. Forthe purposes of making comparisons withthe particulate matter standards, all dataproduced by National Air Monitoring Sta-tions (NAMS), State and Local Air Moni-toring Stations (SLAMS) and other sitessubmitted to EPA in accordance with thepart 58 requirements must be used, and aminimum of 75 percent of the scheduled PM10

samples per quarter are required.(b) To demonstrate attainment of either

the annual or 24-hour standards at a moni-toring site, the monitor must provide suffi-cient data to perform the required calcula-tions of sections 3.0 and 4.0 of this appendix.The amount of data required varies with thesampling frequency, data capture rate andthe number of years of record. In all cases, 3years of representative monitoring data thatmeet the 75 percent criterion of the previousparagraph should be utilized, if available,and would suffice. More than 3 years may beconsidered, if all additional representativeyears of data meeting the 75 percent cri-terion are utilized. Data not meeting thesecriteria may also suffice to show attainment;however, such exceptions will have to be ap-proved by the appropriate Regional Adminis-trator in accordance with EPA guidance.

(c) There are less stringent data require-ments for showing that a monitor has failedan attainment test and thus has recorded aviolation of the particulate matter stand-ards. Although it is generally necessary tomeet the minimum 75 percent data capturerequirement per quarter to use the computa-tional equations described in sections 3.0 and4.0 of this appendix, this criterion does notapply when less data is sufficient to unam-biguously establish nonattainment. The fol-lowing examples illustrate how nonattain-ment can be demonstrated when a site failsto meet the completeness criteria. Non-attainment of the 24-hour primary standardscan be established by the observed annualnumber of exceedances (e.g., four observedexceedances in a single year), or by the esti-mated number of exceedances derived fromthe observed number of exceedances and therequired number of scheduled samples (e.g.,two observed exceedances with every otherday sampling). Nonattainment of the annualstandards can be demonstrated on the basisof quarterly mean concentrations developedfrom observed data combined with one-halfthe minimum detectable concentration sub-stituted for missing values. In both cases, ex-pected annual values must exceed the levelsallowed by the standards.

2.4 Adjustment for Exceptional Events andTrends.


71

Environmental Protection Agency Pt. 50, App. K

(a) An exceptional event is an uncontrol-lable event caused by natural sources of par-ticulate matter or an event that is not ex-pected to recur at a given location. Inclusionof such a value in the computation ofexceedances or averages could result in inap-propriate estimates of their respective ex-pected annual values. To reduce the effect ofunusual events, more than 3 years of rep-resentative data may be used. Alternatively,other techniques, such as the use of statis-tical models or the use of historical datacould be considered so that the event may bediscounted or weighted according to thelikelihood that it will recur. The use of suchtechniques is subject to the approval of theappropriate Regional Administrator in ac-cordance with EPA guidance.

(b) In cases where long–term trends inemissions and air quality are evident, math-ematical techniques should be applied to ac-count for the trends to ensure that the ex-pected annual values are not inappropriatelybiased by unrepresentative data. In the sim-plest case, if 3 years of data are availableunder stable emission conditions, this datashould be used. In the event of a trend orshift in emission patterns, either the mostrecent representative year(s) could be usedor statistical techniques or models could beused in conjunction with previous years ofdata to adjust for trends. The use of lessthan 3 years of data, and any adjustmentsare subject to the approval of the appro-priate Regional Administrator in accordancewith EPA guidance.

3.0 Computational Equations for the 24-hourStandards.

3.1 Estimating Exceedances for a Year.(a) If PM10 sampling is scheduled less fre-

quently than every day, or if some scheduledsamples are missed, a PM10 value will not beavailable for each day of the year. To ac-count for the possible effect of incompletedata, an adjustment must be made to thedata collected at each monitoring locationto estimate the number of exceedances in acalendar year. In this adjustment, the as-sumption is made that the fraction of miss-ing values that would have exceeded thestandard level is identical to the fraction ofmeasured values above this level. This com-putation is to be made for all sites that arescheduled to monitor throughout the entireyear and meet the minimum data require-ments of section 2.3 of this appendix. Be-cause of possible seasonal imbalance, thisadjustment shall be applied on a quarterlybasis. The estimate of the expected numberof exceedances for the quarter is equal to theobserved number of exceedances plus an in-crement associated with the missing data.The following equation must be used forthese computations:

Equation 1

e v v n N n v N nq q q q q q q q q= + ( ) × −( )[ ] = ×

where:

eq = the estimated number of exceedances forcalendar quarter q;

vq = the observed number of exceedances forcalendar quarter q;

Nq = the number of days in calendar quarterq;

nq = the number of days in calendar quarterq with PM10 data; and

q = the index for calendar quarter, q=1, 2, 3or 4.

(b) The estimated number of exceedancesfor a calendar quarter must be rounded tothe nearest hundredth (fractional valuesequal to or greater than 0.005 must be round-ed up).

(c) The estimated number of exceedancesfor the year, e, is the sum of the estimatesfor each calendar quarter.

Equation 2

e eqq

==∑

1

4

(d) The estimated number of exceedancesfor a single year must be rounded to one dec-imal place (fractional values equal to orgreater than 0.05 are to be rounded up). Theexpected number of exceedances is then esti-mated by averaging the individual annual es-timates for the most recent 3 or more rep-resentative years of data. The expected num-ber of exceedances must be rounded to onedecimal place (fractional values equal to orgreater than 0.05 are to be rounded up).

(e) The adjustment for incomplete datawill not be necessary for monitoring or mod-eling data which constitutes a completerecord, i.e., 365 days per year.

(f) To reduce the potential for overesti-mating the number of expected exceedances,the correction for missing data will not berequired for a calendar quarter in which thefirst observed exceedance has occurred if:

(1) There was only one exceedance in thecalendar quarter;

(2) Everyday sampling is subsequently ini-tiated and maintained for 4 calendar quar-ters in accordance with 40 CFR 58.13; and

(3) Data capture of 75 percent is achievedduring the required period of everyday sam-pling. In addition, if the first exceedance isobserved in a calendar quarter in which themonitor is already sampling every day, noadjustment for missing data will be made tothe first exceedance if a 75 percent data cap-ture rate was achieved in the quarter inwhich it was observed.


72

40 CFR Ch. I (7–1–01 Edition)Pt. 50, App. K

Example 1

a. During a particular calendar quarter, 39out of a possible 92 samples were recorded,with one observed exceedance of the 24-hourstandard. Using Equation 1, the estimatednumber of exceedances for the quarter is:

eq=1×92/39=2.359 or 2.36.

b. If the estimated exceedances for theother 3 calendar quarters in the year were2.30, 0.0 and 0.0, then, using Equation 2, theestimated number of exceedances for theyear is 2.36=2.30=0.0=0.0 which equals 4.66 or4.7. If no exceedances were observed for the 2previous years, then the expected number ofexceedances is estimated by: (1/3)×(4.7=0=0)=1.57 or 1.6. Since 1.6 exceeds theallowable number of expected exceedances,this monitoring site would fail the attain-ment test.

Example 2

In this example, everyday sampling wasinitiated following the first observed exceed-ance as required by 40 CFR 58.13. Accord-ingly, the first observed exceedance wouldnot be adjusted for incomplete sampling.During the next three quarters, 1.2exceedances were estimated. In this case, theestimated exceedances for the year would be1.0=1.2=0.0=0.0 which equals 2.2. If, as before,no exceedances were observed for the twoprevious years, then the estimatedexceedances for the 3–year period would thenbe (1/3)×(2.2=0.0=0.0)=0.7, and the monitoringsite would not fail the attainment test.

3.2 Adjustments for Non-Scheduled SamplingDays.

(a) If a systematic sampling schedule isused and sampling is performed on days inaddition to the days specified by the system-atic sampling schedule, e.g., during episodesof high pollution, then an adjustment mustbe made in the eqution for the estimation ofexceedances. Such an adjustment is neededto eliminate the bias in the estimate of thequarterly and annual number of exceedancesthat would occur if the chance of an exceed-ance is different for scheduled than for non-scheduled days, as would be the case withepisode sampling.

(b) The required adjustment treats the sys-tematic sampling schedule as a stratifiedsampling plan. If the period from one sched-uled sample until the day preceding the nextscheduled sample is defined as a samplingstratum, then there is one stratum for eachscheduled sampling day. An average numberof observed exceedances is computed for eachof these sampling strata. With nonscheduledsampling days, the estimated number ofexceedances is defined as:

Equation 3

e N m v kq q q j jj

mq

= ( ) × ( )=∑

1

where:

eq = the estimated number of exceedances forthe quarter;

Nq = the number of days in the quarter;mq = the number of strata with samples dur-

ing the quarter;vj = the number of observed exceedances in

stratum j; andkj = the number of actual samples in stratum

j.

(c) Note that if only one sample value is re-corded in each stratum, then Equation 3 re-duces to Equation 1.

Example 3

A monitoring site samples according to asystematic sampling schedule of one sampleevery 6 days, for a total of 15 scheduled sam-ples in a quarter out of a total of 92 possiblesamples. During one 6-day period, potentialepisode levels of PM10 were suspected, so 5additional samples were taken. One of theregular scheduled samples was missed, so atotal of 19 samples in 14 sampling stratawere measured. The one 6-day sampling stra-tum with 6 samples recorded 2 exceedances.The remainder of the quarter with one sam-ple per stratum recorded zero exceedances.Using Equation 3, the estimated number ofexceedances for the quarter is:

eq=(92/14)×(2/6=0=. . .=0)=2.19.

4.0 Computational Equations for AnnualStandards.

4.1 Calculation of the Annual ArithmeticMean. (a) An annual arithmetic mean valuefor PM10 is determined by averaging thequarterly means for the 4 calendar quartersof the year. The following equation is to beused for calculation of the mean for a cal-endar quarter:

Equation 4

x n xq q ii

nq

= ( ) ×=∑1

1where:

x̄q = the quarterly mean concentration forquarter q, q=1, 2, 3, or 4,

nq = the number of samples in the quarter,and

xi = the ith concentration value recorded inthe quarter.

(b) The quarterly mean, expressed in µg/m3,must be rounded to the nearest tenth (frac-tional values of 0.05 should be rounded up).


73

Environmental Protection Agency Pt. 50, App. L

(c) The annual mean is calculated by usingthe following equation:

Equation 5

x xqq

= ( ) ×=∑1

41

4

where:x̄ = the annual mean; andx̄q = the mean for calendar quarter q.

(d) The average of quarterly means mustbe rounded to the nearest tenth (fractionalvalues of 0.05 should be rounded up).

(e) The use of quarterly averages to com-pute the annual average will not be nec-essary for monitoring or modeling datawhich results in a complete record, i.e., 365days per year.

(f) The expected annual mean is estimatedas the average of three or more annualmeans. This multi-year estimate, expressedin µg/m3, shall be rounded to the nearest in-teger for comparison with the annual stand-ard (fractional values of 0.5 should be round-ed up).

Example 4

Using Equation 4, the quarterly means arecalculated for each calendar quarter. If thequarterly means are 52.4, 75.3, 82.1, and 63.2µg/m 3, then the annual mean is:

x̄ = (1/4)×(52.4=75.3=82.1=63.2) = 68.25 or 68.3.

4.2 Adjustments for Non-scheduled SamplingDays. (a) An adjustment in the calculation ofthe annual mean is needed if sampling is per-formed on days in addition to the days speci-fied by the systematic sampling schedule.For the same reasons given in the discussionof estimated exceedances, under section 3.2of this appendix, the quarterly averageswould be calculated by using the followingequation:

Equation 6

x m x kqq j

m

i

k

ij j

q j

=

× ( )

= =1

1 1Σ Σ

where:x̄q = the quarterly mean concentration for

quarter q, q=1, 2, 3, or 4;xij = the ith concentration value recorded in

stratum j;kj = the number of actual samples in stratum

j; andmq = the number of strata with data in the

quarter.

(b) If one sample value is recorded in eachstratum, Equation 6 reduces to a simplearithmetic average of the observed values asdescribed by Equation 4.

Example 5

a. During one calendar quarter, 9 observa-tions were recorded. These samples were dis-tributed among 7 sampling strata, with 3 ob-servations in one stratum. The concentra-tions of the 3 observations in the single stra-tum were 202, 242, and 180 µg/m3. The remain-ing 6 observed concentrations were 55, 68, 73,92, 120, and 155 µg/m3. Applying the weightingfactors specified in Equation 6, the quarterlymean is:

x̄q = (1/7) × [(1/3) × (202 = 242 = 180) = 155 = 68= 73 = 92 = 120 = 155] = 110.1

b. Although 24-hour measurements arerounded to the nearest 10 µg/m3 for deter-minations of exceedances of the 24-hourstandard, note that these values are roundedto the nearest 1 µg/m3 for the calculation ofmeans.

[62 FR 38712, July 18, 1997]

APPENDIX L TO PART 50—REFERENCEMETHOD FOR THE DETERMINATION OFFINE PARTICULATE MATTER AS PM2.5

IN THE ATMOSPHERE

1.0 Applicability.1.1 This method provides for the measure-

ment of the mass concentration of fine par-ticulate matter having an aerodynamic di-ameter less than or equal to a nominal 2.5micrometers (PM2.5) in ambient air over a 24-hour period for purposes of determiningwhether the primary and secondary nationalambient air quality standards for fine partic-ulate matter specified in § 50.7 of this partare met. The measurement process is consid-ered to be nondestructive, and the PM2.5 sam-ple obtained can be subjected to subsequentphysical or chemical analyses. Quality as-sessment procedures are provided in part 58,appendix A of this chapter, and quality as-surance guidance are provided in references1, 2, and 3 in section 13.0 of this appendix.

1.2 This method will be considered a ref-erence method for purposes of part 58 of thischapter only if:

(a) The associated sampler meets the re-quirements specified in this appendix andthe applicable requirements in part 53 of thischapter, and

(b) The method and associated samplerhave been designated as a reference methodin accordance with part 53 of this chapter.

1.3 PM2.5 samplers that meet nearly allspecifications set forth in this method buthave minor deviations and/or modificationsof the reference method sampler will be des-ignated as ‘‘Class I’’ equivalent methods forPM2.5 in accordance with part 53 of this chap-ter.

2.0 Principle.2.1 An electrically powered air sampler

draws ambient air at a constant volumetricflow rate into a specially shaped inlet and


74

40 CFR Ch. I (7–1–01 Edition)Pt. 50, App. L

through an inertial particle size separator(impactor) where the suspended particulatematter in the PM2.5 size range is separatedfor collection on a polytetrafluoroethylene(PTFE) filter over the specified sampling pe-riod. The air sampler and other aspects ofthis reference method are specified either ex-plicitly in this appendix or generally withreference to other applicable regulations orquality assurance guidance.

2.2 Each filter is weighed (after moistureand temperature conditioning) before andafter sample collection to determine the netgain due to collected PM2.5. The total volumeof air sampled is determined by the samplerfrom the measured flow rate at actual ambi-ent temperature and pressure and the sam-pling time. The mass concentration of PM2.5

in the ambient air is computed as the totalmass of collected particles in the PM2.5 sizerange divided by the actual volume of airsampled, and is expressed in micrograms percubic meter of air (µg/m3).

3.0 PM2.5 Measurement Range.3.1 Lower concentration limit. The lower de-

tection limit of the mass concentrationmeasurement range is estimated to be ap-proximately 2 µg/m3, based on noted masschanges in field blanks in conjunction withthe 24 m3 nominal total air sample volumespecified for the 24-hour sample.

3.2 Upper concentration limit. The upperlimit of the mass concentration range is de-termined by the filter mass loading beyondwhich the sampler can no longer maintainthe operating flow rate within specified lim-its due to increased pressure drop across theloaded filter. This upper limit cannot bespecified precisely because it is a complexfunction of the ambient particle size dis-tribution and type, humidity, the individualfilter used, the capacity of the sampler flowrate control system, and perhaps other fac-tors. Nevertheless, all samplers are esti-mated to be capable of measuring 24-hourPM2.5 mass concentrations of at least 200 µg/m3 while maintaining the operating flow ratewithin the specified limits.

3.3 Sample period. The required sample pe-riod for PM2.5 concentration measurementsby this method shall be 1,380 to 1500 minutes(23 to 25 hours). However, when a sample pe-riod is less than 1,380 minutes, the measuredconcentration (as determined by the col-lected PM2.5 mass divided by the actual sam-pled air volume), multiplied by the actualnumber of minutes in the sample period anddivided by 1,440, may be used as if it were avalid concentration measurement for thespecific purpose of determining a violation ofthe NAAQS. This value assumes that thePM2.5 concentration is zero for the remainingportion of the sample period and thereforerepresents the minimum concentration thatcould have been measured for the full 24-hoursample period. Accordingly, if the value thuscalculated is high enough to be an exceed-

ance, such an exceedance would be a validexceedance for the sample period. When re-ported to AIRS, this data value should re-ceive a special code to identify it as not to becommingled with normal concentrationmeasurements or used for other purposes.

4.0 Accuracy.4.1 Because the size and volatility of the

particles making up ambient particulatematter vary over a wide range and the massconcentration of particles varies with par-ticle size, it is difficult to define the accu-racy of PM2.5 measurements in an absolutesense. The accuracy of PM2.5 measurementsis therefore defined in a relative sense, ref-erenced to measurements provided by thisreference method. Accordingly, accuracyshall be defined as the degree of agreementbetween a subject field PM2.5 sampler and acollocated PM2.5 reference method auditsampler operating simultaneously at themonitoring site location of the subject sam-pler and includes both random (precision)and systematic (bias) errors. The require-ments for this field sampler audit procedureare set forth in part 58, appendix A of thischapter.

4.2 Measurement system bias. Results of col-located measurements where the duplicatesampler is a reference method sampler areused to assess a portion of the measurementsystem bias according to the schedule andprocedure specified in part 58, appendix A ofthis chapter.

4.3 Audits with reference method samplers todetermine system accuracy and bias. Accordingto the schedule and procedure specified inpart 58, appendix A of this chapter, a ref-erence method sampler is required to be lo-cated at each of selected PM2.5 SLAMS sitesas a duplicate sampler. The results from theprimary sampler and the duplicate referencemethod sampler are used to calculate accu-racy of the primary sampler on a quarterlybasis, bias of the primary sampler on an an-nual basis, and bias of a single reporting or-ganization on an annual basis. Reference 2 insection 13.0 of this appendix provides addi-tional information and guidance on thesereference method audits.

4.4 Flow rate accuracy and bias. Part 58, ap-pendix A of this chapter requires that theflow rate accuracy and bias of individualPM2.5 samplers used in SLAMS monitoringnetworks be assessed periodically via auditsof each sampler’s operational flow rate. Inaddition, part 58, appendix A of this chapterrequires that flow rate bias for each ref-erence and equivalent method operated byeach reporting organization be assessedquarterly and annually. Reference 2 in sec-tion 13.0 of this appendix provides additionalinformation and guidance on flow rate accu-racy audits and calculations for accuracyand bias.

5.0 Precision. A data quality objective of 10percent coefficient of variation or better has


75


been established for the operational preci-sion of PM2.5 monitoring data.

5.1 Tests to establish initial operationalprecision for each reference method samplerare specified as a part of the requirementsfor designation as a reference method under§ 53.58 of this chapter.

5.2 Measurement System Precision. Collo-cated sampler results, where the duplicatesampler is not a reference method samplerbut is a sampler of the same designatedmethod as the primary sampler, are used toassess measurement system precision ac-cording to the schedule and procedure speci-fied in part 58, appendix A of this chapter.Part 58, appendix A of this chapter requiresthat these collocated sampler measurementsbe used to calculate quarterly and annualprecision estimates for each primary sam-pler and for each designated method em-ployed by each reporting organization. Ref-erence 2 in section 13.0 of this appendix pro-vides additional information and guidanceon this requirement.

6.0 Filter for PM2.5 Sample Collection. Any fil-ter manufacturer or vendor who sells or of-fers to sell filters specifically identified foruse with this PM2.5 reference method shallcertify that the required number of filtersfrom each lot of filters offered for sale assuch have been tested as specified in this sec-tion 6.0 and meet all of the following designand performance specifications.

6.1 Size. Circular, 46.2 mm diameter ±0.25mm.

6.2 Medium. Polytetrafluoroethylene(PTFE Teflon), with integral support ring.

6.3 Support ring. Polymethylpentene (PMP)or equivalent inert material, 0.38 ±0.04 mmthick, outer diameter 46.2 mm ±0.25 mm, andwidth of 3.68 mm ( ±0.00, -0.51 mm).

6.4 Pore size. 2 µm as measured by ASTM F316–94.

6.5 Filter thickness. 30 to 50 µm.6.6 Maximum pressure drop (clean filter). 30

cm H2O column @ 16.67 L/min clean air flow.6.7 Maximum moisture pickup. Not more

than 10 µg weight increase after 24-hour ex-posure to air of 40 percent relative humidity,relative to weight after 24-hour exposure toair of 35 percent relative humidity.

6.8 Collection efficiency. Greater than 99.7percent, as measured by the DOP test (ASTMD 2986–91) with 0.3 µm particles at the sam-pler’s operating face velocity.

6.9 Filter weight stability. Filter weight lossshall be less than 20 µg, as measured in eachof the following two tests specified in sec-tions 6.9.1 and 6.9.2 of this appendix. The fol-lowing conditions apply to both of thesetests: Filter weight loss shall be the averagedifference between the initial and the finalfilter weights of a random sample of test fil-ters selected from each lot prior to sale. Thenumber of filters tested shall be not lessthan 0.1 percent of the filters of each manu-facturing lot, or 10 filters, whichever is

greater. The filters shall be weighed underlaboratory conditions and shall have had noair sample passed through them, i.e., filterblanks. Each test procedure must includeinitial conditioning and weighing, the test,and final conditioning and weighing. Condi-tioning and weighing shall be in accordancewith sections 8.0 through 8.2 of this appendixand general guidance provided in reference 2of section 13.0 of this appendix.

6.9.1 Test for loose, surface particle contami-nation. After the initial weighing, installeach test filter, in turn, in a filter cassette(Figures L–27, L–28, and L–29 of this appen-dix) and drop the cassette from a height of 25cm to a flat hard surface, such as a particle-free wood bench. Repeat two times, for atotal of three drop tests for each test filter.Remove the test filter from the cassette andweigh the filter. The average change inweight must be less than 20 µg.

6.9.2 Test for temperature stability. Afterweighing each filter, place the test filters ina drying oven set at 40 °C ±2 °C for not lessthan 48 hours. Remove, condition, and re-weigh each test filter. The average change inweight must be less than 20 µg.

6.10 Alkalinity. Less than 25 microequiva-lents/gram of filter, as measured by the guid-ance given in reference 2 in section 13.0 ofthis appendix.

6.11 Supplemental requirements. Althoughnot required for determination of PM2.5 massconcentration under this reference method,additional specifications for the filter mustbe developed by users who intend to subjectPM2.5 filter samples to subsequent chemicalanalysis. These supplemental specificationsinclude background chemical contaminationof the filter and any other filter parametersthat may be required by the method of chem-ical analysis. All such supplemental filterspecifications must be compatible with andsecondary to the primary filter specifica-tions given in this section 6.0 of this appen-dix.

7.0 PM2.5 Sampler.7.1 Configuration. The sampler shall consist

of a sample air inlet, downtube, particle sizeseparator (impactor), filter holder assembly,air pump and flow rate control system, flowrate measurement device, ambient and filtertemperature monitoring system, barometricpressure measurement system, timer, out-door environmental enclosure, and suitablemechanical, electrical, or electronic controlcapability to meet or exceed the design andfunctional performance as specified in thissection 7.0 of this appendix. The performancespecifications require that the sampler:

(a) Provide automatic control of samplevolumetric flow rate and other operationalparameters.

(b) Monitor these operational parametersas well as ambient temperature and pressure.

(c) Provide this information to the sampleroperator at the end of each sample period in


76


digital form, as specified in table L–1 of sec-tion 7.4.19 of this appendix.

7.2 Nature of specifications. The PM2.5 sam-pler is specified by a combination of designand performance requirements. The sampleinlet, downtube, particle size discriminator,filter cassette, and the internal configura-tion of the filter holder assembly are speci-fied explicitly by design figures and associ-ated mechanical dimensions, tolerances, ma-terials, surface finishes, assembly instruc-tions, and other necessary specifications. Allother aspects of the sampler are specified byrequired operational function and perform-ance, and the design of these other aspects(including the design of the lower portion ofthe filter holder assembly) is optional, sub-ject to acceptable operational performance.Test procedures to demonstrate compliancewith both the design and performance re-quirements are set forth in subpart E of part53 of this chapter.

7.3 Design specifications. Except as indicatedin this section 7.3 of this appendix, thesecomponents must be manufactured or repro-duced exactly as specified, in an ISO 9001-registered facility, with registration ini-tially approved and subsequently maintainedduring the period of manufacture. See§ 53.1(t) of this chapter for the definition ofan ISO-registered facility. Minor modifica-tions or variances to one or more compo-nents that clearly would not affect the aero-dynamic performance of the inlet, downtube,impactor, or filter cassette will be consid-ered for specific approval. Any such proposedmodifications shall be described and sub-mitted to the EPA for specific individual ac-ceptability either as part of a reference orequivalent method application under part 53of this chapter or in writing in advance ofsuch an intended application under part 53 ofthis chapter.

7.3.1 Sample inlet assembly. The sample inletassembly, consisting of the inlet, downtube,and impactor shall be configured and assem-bled as indicated in Figure L–1 of this appen-dix and shall meet all associated require-ments. A portion of this assembly shall alsobe subject to the maximum overall samplerleak rate specification under section 7.4.6 ofthis appendix.

7.3.2 Inlet. The sample inlet shall be fab-ricated as indicated in Figures L–2 throughL–18 of this appendix and shall meet all asso-ciated requirements.

7.3.3 Downtube. The downtube shall be fab-ricated as indicated in Figure L–19 of this ap-pendix and shall meet all associated require-ments.

7.3.4 Impactor.7.3.4.1 The impactor (particle size sepa-

rator) shall be fabricated as indicated in Fig-ures L–20 through L–24 of this appendix andshall meet all associated requirements. Fol-lowing the manufacture and finishing of eachupper impactor housing (Figure L–21 of this

appendix), the dimension of the impactionjet must be verified by the manufacturerusing Class ZZ go/no-go plug gauges that aretraceable to NIST.

7.3.4.2 Impactor filter specifications:(a) Size. Circular, 35 to 37 mm diameter.(b) Medium. Borosilicate glass fiber, with-

out binder.(c) Pore size. 1 to 1.5 micrometer, as meas-

ured by ASTM F 316–80.(d) Thickness. 300 to 500 micrometers.7.3.4.3 Impactor oil specifications:(a) Composition. Tetramethyltetraphenyl-

trisiloxane, single-compound diffusion oil.(b) Vapor pressure. Maximum 2 x 10-8 mm

Hg at 25 °C.(c) Viscosity. 36 to 40 centistokes at 25 °C.(d) Density. 1.06 to 1.07 g/cm3 at 25 °C.(e) Quantity. 1 mL ±0.1 mL.7.3.5 Filter holder assembly. The sampler

shall have a sample filter holder assembly toadapt and seal to the down tube and to holdand seal the specified filter, under section 6.0of this appendix, in the sample air stream ina horizontal position below the downtubesuch that the sample air passes downwardthrough the filter at a uniform face velocity.The upper portion of this assembly shall befabricated as indicated in Figures L–25 andL–26 of this appendix and shall accept andseal with the filter cassette, which shall befabricated as indicated in Figures L–27through L–29 of this appendix.

(a) The lower portion of the filter holderassembly shall be of a design and construc-tion that:

(1) Mates with the upper portion of the as-sembly to complete the filter holder assem-bly,

(2) Completes both the external air sealand the internal filter cassette seal suchthat all seals are reliable over repeated filterchangings, and

(3) Facilitates repeated changing of the fil-ter cassette by the sampler operator.

(b) Leak–test performance requirementsfor the filter holder assembly are included insection 7.4.6 of this appendix.

(c) If additional or multiple filters arestored in the sampler as part of an auto-matic sequential sample capability, all suchfilters, unless they are currently and di-rectly installed in a sampling channel orsampling configuration (either active or in-active), shall be covered or (preferably)sealed in such a way as to:

(1) Preclude significant exposure of the fil-ter to possible contamination or accumula-tion of dust, insects, or other material thatmay be present in the ambient air, sampler,or sampler ventilation air during storage pe-riods either before or after sampling; and

(2) To minimize loss of volatile or semi-volatile PM sample components during stor-age of the filter following the sample period.

7.3.6 Flow rate measurement adapter. A flowrate measurement adapter as specified in


77


Figure L–30 of this appendix shall be fur-nished with each sampler.

7.3.7 Surface finish. All internal surfaces ex-posed to sample air prior to the filter shallbe treated electrolytically in a sulfuric acidbath to produce a clear, uniform anodizedsurface finish of not less than 1000 mg/ft2

(1.08 mg/cm2) in accordance with militarystandard specification (mil. spec.) 8625F,Type II, Class 1 in reference 4 of section 13.0of this appendix. This anodic surface coatingshall not be dyed or pigmented. Followinganodization, the surfaces shall be sealed byimmersion in boiling deionized water for notless than 15 minutes. Section 53.51(d)(2) ofthis chapter should also be consulted.

7.3.8 Sampling height. The sampler shall beequipped with legs, a stand, or other meansto maintain the sampler in a stable, uprightposition and such that the center of the sam-ple air entrance to the inlet, during samplecollection, is maintained in a horizontalplane and is 2.0 ±0.2 meters above the floor orother horizontal supporting surface. Suitablebolt holes, brackets, tie-downs, or othermeans should be provided to facilitate me-chanically securing the sample to the sup-porting surface to prevent toppling of thesampler due to wind.

7.4 Performance specifications.7.4.1 Sample flow rate. Proper operation of

the impactor requires that specific air ve-locities be maintained through the device.Therefore, the design sample air flow ratethrough the inlet shall be 16.67 L/min (1.000m3/hour) measured as actual volumetric flowrate at the temperature and pressure of thesample air entering the inlet.

7.4.2 Sample air flow rate control system. Thesampler shall have a sample air flow ratecontrol system which shall be capable of pro-viding a sample air volumetric flow ratewithin the specified range, under section7.4.1 of this appendix, for the specified filter,under section 6.0 of this appendix, at any at-mospheric conditions specified, under sec-tion 7.4.7 of this appendix, at a filter pressuredrop equal to that of a clean filter plus up to75 cm water column (55 mm Hg), and over thespecified range of supply line voltage, undersection 7.4.15.1 of this appendix. This flowcontrol system shall allow for operator ad-justment of the operational flow rate of thesampler over a range of at least ±15 percentof the flow rate specified in section 7.4.1 ofthis appendix.

7.4.3 Sample flow rate regulation. The sampleflow rate shall be regulated such that for thespecified filter, under section 6.0 of this ap-pendix, at any atmospheric conditions speci-fied, under section 7.4.7 of this appendix, at afilter pressure drop equal to that of a cleanfilter plus up to 75 cm water column (55 mmHg), and over the specified range of supplyline voltage, under section 7.4.15.1 of this ap-pendix, the flow rate is regulated as follows:

7.4.3.1 The volumetric flow rate, measuredor averaged over intervals of not more than5 minutes over a 24-hour period, shall notvary more than ±5 percent from the specified16.67 L/min flow rate over the entire sampleperiod.

7.4.3.2 The coefficient of variation (samplestandard deviation divided by the mean) ofthe flow rate, measured over a 24-hour pe-riod, shall not be greater than 2 percent.

7.4.3.3 The amplitude of short-term flowrate pulsations, such as may originate fromsome types of vacuum pumps, shall be at-tenuated such that they do not cause signifi-cant flow measurement error or affect thecollection of particles on the particle collec-tion filter.

7.4.4 Flow rate cut off. The sampler’s sampleair flow rate control system shall terminatesample collection and stop all sample flowfor the remainder of the sample period in theevent that the sample flow rate deviates bymore than 10 percent from the sampler de-sign flow rate specified in section 7.4.1 of thisappendix for more than 60 seconds. However,this sampler cut-off provision shall not applyduring periods when the sampler is inoper-ative due to a temporary power interruption,and the elapsed time of the inoperative pe-riod shall not be included in the total sampletime measured and reported by the sampler,under section 7.4.13 of this appendix.

7.4.5 Flow rate measurement.7.4.5.1 The sampler shall provide a means

to measure and indicate the instantaneoussample air flow rate, which shall be meas-ured as volumetric flow rate at the tempera-ture and pressure of the sample air enteringthe inlet, with an accuracy of ±2 percent.The measured flow rate shall be available fordisplay to the sampler operator at any timein either sampling or standby modes, and themeasurement shall be updated at least every30 seconds. The sampler shall also provide asimple means by which the sampler operatorcan manually start the sample flow tempo-rarily during non-sampling modes of oper-ation, for the purpose of checking the sampleflow rate or the flow rate measurement sys-tem.

7.4.5.2 During each sample period, the sam-pler’s flow rate measurement system shallautomatically monitor the sample volu-metric flow rate, obtaining flow rate meas-urements at intervals of not greater than 30seconds.

(a) Using these interval flow rate measure-ments, the sampler shall determine or cal-culate the following flow-related parameters,scaled in the specified engineering units:

(1) The instantaneous or interval-averageflow rate, in L/min.

(2) The value of the average sample flowrate for the sample period, in L/min.

(3) The value of the coefficient of variation(sample standard deviation divided by the


78


average) of the sample flow rate for the sam-ple period, in percent.

(4) The occurrence of any time intervalduring the sample period in which the meas-ured sample flow rate exceeds a range of ±5percent of the average flow rate for the sam-ple period for more than 5 minutes, in whichcase a warning flag indicator shall be set.

(5) The value of the integrated total sam-ple volume for the sample period, in m3.

(b) Determination or calculation of thesevalues shall properly exclude periods whenthe sampler is inoperative due to temporaryinterruption of electrical power, under sec-tion 7.4.13 of this appendix, or flow rate cutoff, under section 7.4.4 of this appendix.

(c) These parameters shall be accessible tothe sampler operator as specified in table L–1 of section 7.4.19 of this appendix. In addi-tion, it is strongly encouraged that the flowrate for each 5-minute interval during thesample period be available to the operatorfollowing the end of the sample period.

7.4.6 Leak test capability.7.4.6.1 External leakage. The sampler shall

include an external air leak-test capabilityconsisting of components, accessory hard-ware, operator interface controls, a writtenprocedure in the associated Operation/In-struction Manual, under section 7.4.18 of thisappendix, and all other necessary functionalcapability to permit and facilitate the sam-pler operator to conveniently carry out aleak test of the sampler at a field moni-toring site without additional equipment.The sampler components to be subjected tothis leak test include all components andtheir interconnections in which external airleakage would or could cause an error in thesampler’s measurement of the total volumeof sample air that passes through the samplefilter.

(a) The suggested technique for the oper-ator to use for this leak test is as follows:

(1) Remove the sampler inlet and installsthe flow rate measurement adapter suppliedwith the sampler, under section 7.3.6 of thisappendix.

(2) Close the valve on the flow rate meas-urement adapter and use the sampler airpump to draw a partial vacuum in the sam-pler, including (at least) the impactor, filterholder assembly (filter in place), flow meas-urement device, and interconnections be-tween these devices, of at least 55 mm Hg (75cm water column), measured at a locationdownstream of the filter holder assembly.

(3) Plug the flow system downstream ofthese components to isolate the componentsunder vacuum from the pump, such as with abuilt-in valve.

(4) Stop the pump.(5) Measure the trapped vacuum in the

sampler with a built-in pressure measuringdevice.

(6) (i) Measure the vacuum in the samplerwith the built-in pressure measuring device

again at a later time at least 10 minutesafter the first pressure measurement.

(ii) CAUTION: Following completion of thetest, the adaptor valve should be openedslowly to limit the flow rate of air into thesampler. Excessive air flow rate may blowoil out of the impactor.

(7) Upon completion of the test, open theadaptor valve, remove the adaptor and plugs,and restore the sampler to the normal oper-ating configuration.

(b) The associated leak test procedureshall require that for successful passage ofthis test, the difference between the twopressure measurements shall not be greaterthan the number of mm of Hg specified forthe sampler by the manufacturer, based onthe actual internal volume of the sampler,that indicates a leak of less than 80 mL/min.

(c) Variations of the suggested techniqueor an alternative external leak test tech-nique may be required for samplers whosedesign or configuration would make the sug-gested technique impossible or impractical.The specific proposed external leak test pro-cedure, or particularly an alternative leaktest technique, proposed for a particular can-didate sampler may be described and sub-mitted to the EPA for specific individual ac-ceptability either as part of a reference orequivalent method application under part 53of this chapter or in writing in advance ofsuch an intended application under part 53 ofthis chapter.

7.4.6.2 Internal, filter bypass leakage. Thesampler shall include an internal, filter by-pass leak-check capability consisting ofcomponents, accessory hardware, operatorinterface controls, a written procedure in theOperation/Instruction Manual, and all othernecessary functional capability to permitand facilitate the sampler operator to con-veniently carry out a test for internal filterbypass leakage in the sampler at a fieldmonitoring site without additional equip-ment. The purpose of the test is to determinethat any portion of the sample flow rate thatleaks past the sample filter without passingthrough the filter is insignificant relative tothe design flow rate for the sampler.

(a) The suggested technique for the oper-ator to use for this leak test is as follows:

(1) Carry out an external leak test as pro-vided under section 7.4.6.1 of this appendixwhich indicates successful passage of theprescribed external leak test.

(2) Install a flow-impervious membranematerial in the filter cassette, either with orwithout a filter, as appropriate, which effec-tively prevents air flow through the filter.

(3) Use the sampler air pump to draw a par-tial vacuum in the sampler, downstream ofthe filter holder assembly, of at least 55 mmHg (75 cm water column).

(4) Plug the flow system downstream of thefilter holder to isolate the components under


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vacuum from the pump, such as with a built-in valve.

(5) Stop the pump.(6) Measure the trapped vacuum in the

sampler with a built-in pressure measuringdevice.

(7) Measure the vacuum in the samplerwith the built-in pressure measuring deviceagain at a later time at least 10 minutesafter the first pressure measurement.

(8) Remove the flow plug and membraneand restore the sampler to the normal oper-ating configuration.

(b) The associated leak test procedureshall require that for successful passage ofthis test, the difference between the twopressure measurements shall not be greaterthan the number of mm of Hg specified forthe sampler by the manufacturer, based onthe actual internal volume of the portion ofthe sampler under vacuum, that indicates aleak of less than 80 mL/min.

(c) Variations of the suggested techniqueor an alternative internal, filter bypass leaktest technique may be required for samplerswhose design or configuration would makethe suggested technique impossible or im-practical. The specific proposed internal leaktest procedure, or particularly an alternativeinternal leak test technique proposed for aparticular candidate sampler may be de-scribed and submitted to the EPA for spe-cific individual acceptability either as partof a reference or equivalent method applica-tion under part 53 of this chapter or in writ-ing in advance of such intended applicationunder part 53 of this chapter.

7.4.7 Range of operational conditions. Thesampler is required to operate properly andmeet all requirements specified in this ap-pendix over the following operational ranges.

7.4.7.1 Ambient temperature. -30 to =45 °C(Note: Although for practical reasons, thetemperature range over which samplers arerequired to be tested under part 53 of thischapter is -20 to =40 °C, the sampler shall bedesigned to operate properly over this widertemperature range.).

7.4.7.2 Ambient relative humidity. 0 to 100percent.

7.4.7.3 Barometric pressure range. 600 to 800mm Hg.

7.4.8 Ambient temperature sensor. The sam-pler shall have capability to measure thetemperature of the ambient air surroundingthe sampler over the range of -30 to =45 °C,with a resolution of 0.1 °C and accuracy of±2.0 °C, referenced as described in reference 3in section 13.0 of this appendix, with andwithout maximum solar insolation.

7.4.8.1 The ambient temperature sensorshall be mounted external to the sampler en-closure and shall have a passive, naturallyventilated sun shield. The sensor shall be lo-cated such that the entire sun shield is atleast 5 cm above the horizontal plane of thesampler case or enclosure (disregarding the

inlet and downtube) and external to thevertical plane of the nearest side or protu-berance of the sampler case or enclosure.The maximum temperature measurementerror of the ambient temperature measure-ment system shall be less than 1.6 °C at 1 m/s wind speed and 1000 W/m2 solar radiationintensity.

7.4.8.2 The ambient temperature sensorshall be of such a design and mounted insuch a way as to facilitate its convenientdismounting and immersion in a liquid forcalibration and comparison to the filter tem-perature sensor, under section 7.4.11 of thisappendix.

7.4.8.3 This ambient temperature measure-ment shall be updated at least every 30 sec-onds during both sampling and standby (non-sampling) modes of operation. A visual indi-cation of the current (most recent) value ofthe ambient temperature measurement, up-dated at least every 30 seconds, shall beavailable to the sampler operator duringboth sampling and standby (non-sampling)modes of operation, as specified in table L–1of section 7.4.19 of this appendix.

7.4.8.4 This ambient temperature measure-ment shall be used for the purpose of moni-toring filter temperature deviation from am-bient temperature, as required by section7.4.11 of this appendix, and may be used forpurposes of effecting filter temperature con-trol, under section 7.4.10 of this appendix, orcomputation of volumetric flow rate, undersections 7.4.1 to 7.4.5 of this appendix, if ap-propriate.

7.4.8.5 Following the end of each sample pe-riod, the sampler shall report the maximum,minimum, and average temperature for thesample period, as specified in table L–1 ofsection 7.4.19 of this appendix.

7.4.9 Ambient barometric sensor. The samplershall have capability to measure the baro-metric pressure of the air surrounding thesampler over a range of 600 to 800 mm Hg ref-erenced as described in reference 3 in section13.0 of this appendix; also see part 53, subpartE of this chapter. This barometric pressuremeasurement shall have a resolution of 5mm Hg and an accuracy of ±10 mm Hg andshall be updated at least every 30 seconds. Avisual indication of the value of the current(most recent) barometric pressure measure-ment, updated at least every 30 seconds,shall be available to the sampler operatorduring both sampling and standby (non-sam-pling) modes of operation, as specified intable L–1 of section 7.4.19 of this appendix.This barometric pressure measurement maybe used for purposes of computation of volu-metric flow rate, under sections 7.4.1 to 7.4.5of this appendix, if appropriate. Followingthe end of a sample period, the sampler shallreport the maximum, minimum, and meanbarometric pressures for the sample period,as specified in table L–1 of section 7.4.19 ofthis appendix.


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7.4.10 Filter temperature control (samplingand post-sampling). The sampler shall providea means to limit the temperature rise of thesample filter (all sample filters for sequen-tial samplers), from insolation and othersources, to no more 5 °C above the tempera-ture of the ambient air surrounding the sam-pler, during both sampling and post-sam-pling periods of operation. The post-sam-pling period is the non-sampling period be-tween the end of the active sampling periodand the time of retrieval of the sample filterby the sampler operator.

7.4.11 Filter temperature sensor(s).7.4.11.1 The sampler shall have the capa-

bility to monitor the temperature of thesample filter (all sample filters for sequen-tial samplers) over the range of -30 to =45 °Cduring both sampling and non-sampling peri-ods. While the exact location of this tem-perature sensor is not explicitly specified,the filter temperature measurement systemmust demonstrate agreement, within 1 °C,with a test temperature sensor located with-in 1 cm of the center of the filter down-stream of the filter during both samplingand non-sampling modes, as specified in thefilter temperature measurement test de-scribed in part 53, subpart E of this chapter.This filter temperature measurement shallhave a resolution of 0.1 °C and accuracy of±1.0 °C, referenced as described in reference 3in section 13.0 of this appendix. This tem-perature sensor shall be of such a design andmounted in such a way as to facilitate itsreasonably convenient dismounting and im-mersion in a liquid for calibration and com-parison to the ambient temperature sensorunder section 7.4.8 of this appendix.

7.4.11.2 The filter temperature measure-ment shall be updated at least every 30 sec-onds during both sampling and standby (non-sampling) modes of operation. A visual indi-cation of the current (most recent) value ofthe filter temperature measurement, up-dated at least every 30 seconds, shall beavailable to the sampler operator duringboth sampling and standby (non-sampling)modes of operation, as specified in table L–1of section 7.4.19 of this appendix.

7.4.11.3 For sequential samplers, the tem-perature of each filter shall be measured in-dividually unless it can be shown, as speci-fied in the filter temperature measurementtest described in § 53.57 of this chapter, thatthe temperature of each filter can be rep-resented by fewer temperature sensors.

7.4.11.4 The sampler shall also provide awarning flag indicator following any occur-rence in which the filter temperature (anyfilter temperature for sequential samplers)exceeds the ambient temperature by morethan 5 °C for more than 30 consecutive min-utes during either the sampling or post-sam-pling periods of operation, as specified intable L–1 of section 7.4.19 of this appendix,under section 10.12 of this appendix, regard-

ing sample validity when a warning flag oc-curs. It is further recommended (not re-quired) that the sampler be capable of re-cording the maximum differential betweenthe measured filter temperature and the am-bient temperature and its time and date ofoccurrence during both sampling and post-sampling (non-sampling) modes of operationand providing for those data to be accessibleto the sampler operator following the end ofthe sample period, as suggested in table L–1of section 7.4.19 of this appendix.

7.4.12 Clock/timer system.(a) The sampler shall have a programmable

real-time clock timing/control system that:(1) Is capable of maintaining local time

and date, including year, month, day-of-month, hour, minute, and second to an accu-racy of ±1.0 minute per month.

(2) Provides a visual indication of the cur-rent system time, including year, month,day-of-month, hour, and minute, updated atleast each minute, for operator verification.

(3) Provides appropriate operator controlsfor setting the correct local time and date.

(4) Is capable of starting the sample collec-tion period and sample air flow at a specific,operator-settable time and date, and stop-ping the sample air flow and terminating thesampler collection period 24 hours (1440 min-utes) later, or at a specific, operator-settabletime and date.

(b) These start and stop times shall bereadily settable by the sampler operator towithin ±1.0 minute. The system shall providea visual indication of the current start andstop time settings, readable to ±1.0 minute,for verification by the operator, and thestart and stop times shall also be availablevia the data output port, as specified in tableL–1 of section 7.4.19 of this appendix. Uponexecution of a programmed sample periodstart, the sampler shall automatically resetall sample period information and warningflag indications pertaining to a previoussample period. Refer also to section 7.4.15.4of this appendix regarding retention of cur-rent date and time and programmed startand stop times during a temporary electricalpower interruption.

7.4.13 Sample time determination. The sam-pler shall be capable of determining theelapsed sample collection time for each PM2.5

sample, accurate to within ±1.0 minute,measured as the time between the start ofthe sampling period, under section 7.4.12 ofthis appendix and the termination of thesample period, under section 7.4.12 of this ap-pendix or section 7.4.4 of this appendix. Thiselapsed sample time shall not include peri-ods when the sampler is inoperative due to atemporary interruption of electrical power,under section 7.4.15.4 of this appendix. In theevent that the elapsed sample time deter-mined for the sample period is not within the


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range specified for the required sample pe-riod in section 3.3 of this appendix, the sam-pler shall set a warning flag indicator. Thedate and time of the start of the sample pe-riod, the value of the elapsed sample time forthe sample period, and the flag indicator sta-tus shall be available to the sampler oper-ator following the end of the sample period,as specified in table L–1 of section 7.4.19 ofthis appendix.

7.4.14 Outdoor environmental enclosure. Thesampler shall have an outdoor enclosure (orenclosures) suitable to protect the filter andother non-weatherproof components of thesampler from precipitation, wind, dust, ex-tremes of temperature and humidity; to helpmaintain temperature control of the filter(or filters, for sequential samplers); and toprovide reasonable security for sampler com-ponents and settings.

7.4.15 Electrical power supply.7.4.15.1 The sampler shall be operable and

function as specified herein when operatedon an electrical power supply voltage of 105to 125 volts AC (RMS) at a frequency of 59 to61 Hz. Optional operation as specified at ad-ditional power supply voltages and/or fre-quencies shall not be precluded by this re-quirement.

7.4.15.2 The design and construction of thesampler shall comply with all applicable Na-tional Electrical Code and Underwriters Lab-oratories electrical safety requirements.

7.4.15.3 The design of all electrical andelectronic controls shall be such as to pro-vide reasonable resistance to interference ormalfunction from ordinary or typical levelsof stray electromagnetic fields (EMF) asmay be found at various monitoring sitesand from typical levels of electrical tran-sients or electronic noise as may often or oc-casionally be present on various electricalpower lines.

7.4.15.4 In the event of temporary loss ofelectrical supply power to the sampler, thesampler shall not be required to sample orprovide other specified functions during suchloss of power, except that the internal clock/timer system shall maintain its local timeand date setting within ±1 minute per week,and the sampler shall retain all other timeand programmable settings and all data re-quired to be available to the sampler oper-ator following each sample period for atleast 7 days without electrical supply power.When electrical power is absent at the oper-ator-set time for starting a sample period oris interrupted during a sample period, thesampler shall automatically start or resumesampling when electrical power is restored,if such restoration of power occurs before theoperator-set stop time for the sample period.

7.4.15.5 The sampler shall have the capa-bility to record and retain a record of theyear, month, day-of-month, hour, andminute of the start of each power interrup-tion of more than 1 minute duration, up to 10

such power interruptions per sample period.(More than 10 such power interruptions shallinvalidate the sample, except where an ex-ceedance is measured, under section 3.3 ofthis appendix.) The sampler shall provide forthese power interruption data to be availableto the sampler operator following the end ofthe sample period, as specified in table L–1 ofsection 7.4.19 of this appendix.

7.4.16 Control devices and operator interface.The sampler shall have mechanical, elec-trical, or electronic controls, control de-vices, electrical or electronic circuits as nec-essary to provide the timing, flow rate meas-urement and control, temperature control,data storage and computation, operatorinterface, and other functions specified. Op-erator-accessible controls, data displays, andinterface devices shall be designed to be sim-ple, straightforward, reliable, and easy tolearn, read, and operate under field condi-tions. The sampler shall have provision foroperator input and storage of up to 64 char-acters of numeric (or alphanumeric) data forpurposes of site, sampler, and sample identi-fication. This information shall be availableto the sampler operator for verification andchange and for output via the data outputport along with other data following the endof a sample period, as specified in table L–1of section 7.4.19 of this appendix. All data re-quired to be available to the operator fol-lowing a sample collection period or ob-tained during standby mode in a post-sam-pling period shall be retained by the sampleruntil reset, either manually by the operatoror automatically by the sampler upon initi-ation of a new sample collection period.

7.4.17 Data output port requirement. Thesampler shall have a standard RS–232C dataoutput connection through which digitaldata may be exported to an external datastorage or transmission device. All informa-tion which is required to be available at theend of each sample period shall be accessiblethrough this data output connection. The in-formation that shall be accessible thoughthis output port is summarized in table L–1of section 7.4.19 of this appendix. Since nospecific format for the output data is pro-vided, the sampler manufacturer or vendorshall make available to sampler purchasersappropriate computer software capable of re-ceiving exported sampler data and correctlytranslating the data into a standard spread-sheet format and optionally any other for-mats as may be useful to sampler users. Thisrequirement shall not preclude the samplerfrom offering other types of output connec-tions in addition to the required RS–232Cport.

7.4.18 Operation/instruction manual. Thesampler shall include an associated com-prehensive operation or instruction manual,as required by part 53 of this chapter, whichincludes detailed operating instructions on


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the setup, operation, calibration, and main-tenance of the sampler. This manual shallprovide complete and detailed descriptions ofthe operational and calibration proceduresprescribed for field use of the sampler and allinstruments utilized as part of this referencemethod. The manual shall include adequatewarning of potential safety hazards that mayresult from normal use or malfunction of themethod and a description of necessary safety

precautions. The manual shall also include aclear description of all procedures pertainingto installation, operation, periodic and cor-rective maintenance, and troubleshooting,and shall include parts identification dia-grams.

7.4.19 Data reporting requirements. The var-ious information that the sampler is re-quired to provide and how it is to be providedis summarized in the following table L–1.

TABLE L–1—SUMMARY OF INFORMATION TO BE PROVIDED BY THE SAMPLER

Information to beprovided

Appen-dix L

sectionref-

erence

Availability Format

Anytime1 End of pe-riod2

Visual dis-play3 Data output4 Digital reading5 Units

Flow rate, 30-sec-ond maximuminterval.

7.4.5.1 ✔ .................... ✔ * XX.X ................... L/min

Flow rate, aver-age for thesample period.

7.4.5.2 * ✔ * ✔ XX.X ................... L/min

Flow rate, CV, forsample period.

7.4.5.2 * ✔ * ✔ 0 XX.X ................... %

Flow rate, 5-min.average out ofspec. (FLAG6).

7.4.5.2 ✔ ✔ ✔ ✔ 0 On/Off ................

Sample volume,total.

7.4.5.2 * ✔ ✔ ✔ 0 XX.X ................... m3

Temperature, am-bient, 30-sec-ond interval.

7.4.8 .... ✔ .................... ✔ .................... XX.X ................... °C

Temperature, am-bient, min.,max., averagefor the sampleperiod.

7.4.8 .... * ✔ ✔ ✔ 0 XX.X ................... °C

Baro pressure,ambient, 30-second interval.

7.4.9 .... ✔ .................... ✔ .................... XXX .................... mm Hg

Baro pressure,ambient, min.,max., averagefor the sampleperiod.

7.4.9 .... * ✔ ✔ ✔ 0 XXX .................... mm Hg

Filter temperature,30-second inter-val.

7.4.11 .. ✔ .................... ✔ .................... XX.X ................... °C

Filter temperaturedifferential, 30-second interval,out of spec.(FLAG6).

7.4.11 .. * ✔ ✔ ✔ 0 On/Off ................

Filter temperature,maximum dif-ferential fromambient, date,time of occur-rence.

7.4.11 .. * * * * X.X, YY/MM/DDHH:mm.

°C, Yr./Mon./DayHrs. min

Date and time ..... 7.4.12 .. ✔ .................... ✔ .................... YY/MM/DDHH:mm.

Yr./Mon./Day Hrs.min

Sample start andstop time set-tings.

7.4.12 .. ✔ ✔ ✔ ✔ YY/MM/DDHH:mm.


Sample periodstart time.

7.4.12 .. .................... ✔ ✔ ✔ 0 YYYY/MM/DDHH:mm.


Elapsed sampletime.

7.4.13 .. * ✔ ✔ ✔ 0 HH:mm ............... Hrs. min

Elapsed sampletime, out ofspec. (FLAG6).

7.4.13 .. .................... ✔ ✔ ✔ 0 On/Off ................


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TABLE L–1—SUMMARY OF INFORMATION TO BE PROVIDED BY THE SAMPLER—Continued

Information to beprovided

Appen-dix L

sectionref-

erence

Availability Format

Anytime1 End of pe-riod2

Visual dis-play3 Data output4 Digital reading5 Units

Power interrup-tions ™1 min.,start time of first10.

7.4.15.5 * ✔ * ✔ 1HH:mm,2HH:mm, etc....

Hrs. min

User-entered in-formation, suchas sampler andsite identifica-tion.

7.4.16 .. ✔ ✔ ✔ ✔ 0 As entered .........

✔ Provision of this information is required.*Provision of this information is optional. If information related to the entire sample period is optionally provided prior to the end

of the sample period, the value provided should be the value calculated for the portion of the sampler period completed up to thetime the information is provided.

0 Indicates that this information is also required to be provided to the AIRS data bank; see § § 58.26 and 58.35 of this chapter.

1 Information is required to be available to the operator at any time the sampler is operating, whether sampling or not.2 Information relates to the entire sampler period and must be provided following the end of the sample period until reset

manually by the operator or automatically by the sampler upon the start of a new sample period.3 Information shall be available to the operator visually.4 Information is to be available as digital data at the sampler’s data output port specified in section 7.4.16 of this appendix fol-

lowing the end of the sample period until reset manually by the operator or automatically by the sampler upon the start of a newsample period.

5 Digital readings, both visual and data output, shall have not less than the number of significant digits and resolution speci-fied.

6 Flag warnings may be displayed to the operator by a single-flag indicator or each flag may be displayed individually. Only aset (on) flag warning must be indicated; an off (unset) flag may be indicated by the absence of a flag warning. Sampler usersshould refer to section 10.12 of this appendix regarding the validity of samples for which the sampler provided an associated flagwarning.

8.0 Filter Weighing. See reference 2 in sec-tion 13.0 of this appendix, for additional,more detailed guidance.

8.1 Analytical balance. The analytical bal-ance used to weigh filters must be suitablefor weighing the type and size of filters spec-ified, under section 6.0 of this appendix, andhave a readability of ±1 µg. The balance shallbe calibrated as specified by the manufac-turer at installation and recalibrated imme-diately prior to each weighing session. Seereference 2 in section 13.0 of this appendix foradditional guidance.

8.2 Filter conditioning. All sample filtersused shall be conditioned immediately beforeboth the pre- and post-sampling weighings asspecified below. See reference 2 in section13.0 of this appendix for additional guidance.

8.2.1 Mean temperature. 20 - 23 °C.8.2.2 Temperature control. ±2 °C over 24

hours.8.2.3 Mean humidity. Generally, 30–40 per-

cent relative humidity; however, where itcan be shown that the mean ambient relativehumidity during sampling is less than 30 per-cent, conditioning is permissible at a meanrelative humidity within ±5 relative humid-ity percent of the mean ambient relative hu-midity during sampling, but not less than 20percent.

8.2.4 Humidity control. ±5 relative humiditypercent over 24 hours.

8.2.5 Conditioning time. Not less than 24hours.

8.3 Weighing procedure.

8.3.1 New filters should be placed in theconditioning environment immediately uponarrival and stored there until the pre-sam-pling weighing. See reference 2 in section 13.0of this appendix for additional guidance.

8.3.2 The analytical balance shall be lo-cated in the same controlled environment inwhich the filters are conditioned. The filtersshall be weighed immediately following theconditioning period without intermediate ortransient exposure to other conditions or en-vironments.

8.3.3 Filters must be conditioned at thesame conditions (humidity within ±5 relativehumidity percent) before both the pre- andpost-sampling weighings.

8.3.4 Both the pre- and post-samplingweighings should be carried out on the sameanalytical balance, using an effective tech-nique to neutralize static charges on the fil-ter, under reference 2 in section 13.0 of thisappendix. If possible, both weighings shouldbe carried out by the same analyst.

8.3.5 The pre-sampling (tare) weighing shallbe within 30 days of the sampling period.

8.3.6 The post-sampling conditioning andweighing shall be completed within 240 hours(10 days) after the end of the sample period,unless the filter sample is maintained at 4 °Cor less during the entire time between re-trieval from the sampler and the start of theconditioning, in which case the period shallnot exceed 30 days. Reference 2 in section13.0 of this appendix has additional guidanceon transport of cooled filters.


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8.3.7 Filter blanks.8.3.7.1 New field blank filters shall be

weighed along with the pre-sampling (tare)weighing of each lot of PM2.5 filters. Theseblank filters shall be transported to the sam-pling site, installed in the sampler, retrievedfrom the sampler without sampling, and re-weighed as a quality control check.

8.3.7.2 New laboratory blank filters shall beweighed along with the pre-sampling (tare)weighing of each set of PM2.5 filters. Theselaboratory blank filters should remain in thelaboratory in protective containers duringthe field sampling and should be reweighedas a quality control check.

8.3.8 Additional guidance for proper filterweighing and related quality assurance ac-tivities is provided in reference 2 in section13.0 of this appendix.

9.0 Calibration. Reference 2 in section 13.0 ofthis appendix contains additional guidance.

9.1 General requirements.9.1.1 Multipoint calibration and single-

point verification of the sampler’s flow ratemeasurement device must be performed peri-odically to establish and maintaintraceability of subsequent flow measure-ments to a flow rate standard.

9.1.2 An authoritative flow rate standardshall be used for calibrating or verifying thesampler’s flow rate measurement device withan accuracy of ±2 percent. The flow ratestandard shall be a separate, stand-alone de-vice designed to connect to the flow ratemeasurement adapter, Figure L–30 of this ap-pendix. This flow rate standard must haveits own certification and be traceable to aNational Institute of Standards and Tech-nology (NIST) primary standard for volumeor flow rate. If adjustments to the sampler’sflow rate measurement system calibrationare to be made in conjunction with an auditof the sampler’s flow measurement system,such adjustments shall be made followingthe audit. Reference 2 in section 13.0 of thisappendix contains additional guidance.

9.1.3 The sampler’s flow rate measurementdevice shall be re-calibrated afterelectromechanical maintenance or transportof the sampler.

9.2 Flow rate calibration/verification proce-dure.

9.2.1 PM2.5 samplers may employ varioustypes of flow control and flow measurementdevices. The specific procedure used for cali-bration or verification of the flow rate meas-urement device will vary depending on thetype of flow rate controller and flow ratemeasurement employed. Calibration shall bein terms of actual ambient volumetric flowrates (Qa), measured at the sampler’s inletdowntube. The generic procedure given hereserves to illustrate the general steps in-volved in the calibration of a PM2.5 sampler.The sampler operation/instruction manualrequired under section 7.4.18 of this appendixand the Quality Assurance Handbook in ref-

erence 2 in section 13.0 of this appendix pro-vide more specific and detailed guidance forcalibration.

9.2.2 The flow rate standard used for flowrate calibration shall have its own certifi-cation and be traceable to a NIST primarystandard for volume or flow rate. A calibra-tion relationship for the flow rate standard,e.g., an equation, curve, or family of curvesrelating actual flow rate (Qa) to the flow rateindicator reading, shall be established that isaccurate to within 2 percent over the ex-pected range of ambient temperatures andpressures at which the flow rate standardmay be used. The flow rate standard must bere-calibrated or re-verified at least annually.

9.2.3 The sampler flow rate measurementdevice shall be calibrated or verified by re-moving the sampler inlet and connecting theflow rate standard to the sampler’s downtubein accordance with the operation/instructionmanual, such that the flow rate standard ac-curately measures the sampler’s flow rate.The sampler operator shall first carry out asampler leak check and confirm that thesampler passes the leak test and then verifythat no leaks exist between the flow ratestandard and the sampler.

9.2.4 The calibration relationship betweenthe flow rate (in actual L/min) indicated bythe flow rate standard and by the sampler’sflow rate measurement device shall be estab-lished or verified in accordance with thesampler operation/instruction manual. Tem-perature and pressure corrections to the flowrate indicated by the flow rate standard maybe required for certain types of flow ratestandards. Calibration of the sampler’s flowrate measurement device shall consist of atleast three separate flow rate measurements(multipoint calibration) evenly spaced with-in the range of -10 percent to =10 percent ofthe sampler’s operational flow rate, section7.4.1 of this appendix. Verification of thesampler’s flow rate shall consist of one flowrate measurement at the sampler’s oper-ational flow rate. The sampler operation/in-struction manual and reference 2 in section13.0 of this appendix provide additional guid-ance.

9.2.5 If during a flow rate verification thereading of the sampler’s flow rate indicatoror measurement device differs by ± 4 percentor more from the flow rate measured by theflow rate standard, a new multipoint calibra-tion shall be performed and the flow rateverification must then be repeated.

9.2.6 Following the calibration orverification, the flow rate standard shall beremoved from the sampler and the samplerinlet shall be reinstalled. Then the sampler’snormal operating flow rate (in L/min) shallbe determined with a clean filter in place. Ifthe flow rate indicated by the sampler differsby ±2 percent or more from the required sam-pler flow rate, the sampler flow rate must be


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adjusted to the required flow rate, under sec-tion 7.4.1 of this appendix.

9.3 Periodic calibration or verification ofthe calibration of the sampler’s ambienttemperature, filter temperature, and baro-metric pressure measurement systems is alsorequired. Reference 3 of section 13.0 of thisappendix contains additional guidance.

10.0 PM2.5 Measurement Procedure. The de-tailed procedure for obtaining valid PM2.5

measurements with each specific samplerdesignated as part of a reference method forPM2.5 under part 53 of this chapter shall beprovided in the sampler-specific operation orinstruction manual required by section 7.4.18of this appendix. Supplemental guidance isprovided in section 2.12 of the Quality Assur-ance Handbook listed in reference 2 in sec-tion 13.0 of this appendix. The generic proce-dure given here serves to illustrate the gen-eral steps involved in the PM2.5 sample col-lection and measurement, using a PM2.5 ref-erence method sampler.

10.1 The sampler shall be set up, calibrated,and operated in accordance with the specific,detailed guidance provided in the specificsampler’s operation or instruction manualand in accordance with a specific quality as-surance program developed and establishedby the user, based on applicable supple-mentary guidance provided in reference 2 insection 13.0 of this appendix.

10.2 Each new sample filter shall be in-spected for correct type and size and for pin-holes, particles, and other imperfections. Un-acceptable filters should be discarded. Aunique identification number shall be as-signed to each filter, and an informationrecord shall be established for each filter. Ifthe filter identification number is not orcannot be marked directly on the filter, al-ternative means, such as a number-identifiedstorage container, must be established tomaintain positive filter identification.

10.3 Each filter shall be conditioned in theconditioning environment in accordancewith the requirements specified in section 8.2of this appendix.

10.4 Following conditioning, each filtershall be weighed in accordance with the re-quirements specified in section 8.0 of this ap-pendix and the presampling weight recordedwith the filter identification number.

10.5 A numbered and preweighed filter shallbe installed in the sampler following the in-structions provided in the sampler operationor instruction manual.

10.6 The sampler shall be checked and pre-pared for sample collection in accordancewith instructions provided in the sampler op-eration or instruction manual and with thespecific quality assurance program estab-lished for the sampler by the user.

10.7 The sampler’s timer shall be set tostart the sample collection at the beginningof the desired sample period and stop thesample collection 24 hours later.

10.8 Information related to the sample col-lection (site location or identification num-ber, sample date, filter identification num-ber, and sampler model and serial number)shall be recorded and, if appropriate, enteredinto the sampler.

10.9 The sampler shall be allowed to collectthe PM2.5 sample during the set 24-hour timeperiod.

10.10 Within 96 hours of the end of the sam-ple collection period, the filter, while stillcontained in the filter cassette, shall becarefully removed from the sampler, fol-lowing the procedure provided in the sampleroperation or instruction manual and thequality assurance program, and placed in aprotective container. The protective con-tainer shall contain no loose material thatcould be transferred to the filter. The protec-tive container shall hold the filter cassettesecurely such that the cover shall not comein contact with the filter’s surfaces. Ref-erence 2 in section 13.0 of this appendix con-tains additional information.

10.11 The total sample volume in actual m3

for the sampling period and the elapsed sam-ple time shall be obtained from the samplerand recorded in accordance with the instruc-tions provided in the sampler operation orinstruction manual. All sampler warningflag indications and other information re-quired by the local quality assurance pro-gram shall also be recorded.

10.12 All factors related to the validity orrepresentativeness of the sample, such assampler tampering or malfunctions, unusualmeteorological conditions, construction ac-tivity, fires or dust storms, etc. shall be re-corded as required by the local quality assur-ance program. The occurrence of a flag warn-ing during a sample period shall not nec-essarily indicate an invalid sample but rath-er shall indicate the need for specific reviewof the QC data by a quality assurance officerto determine sample validity.

10.13 After retrieval from the sampler, theexposed filter containing the PM2.5 sampleshould be transported to the filter condi-tioning environment as soon as possibleideally to arrive at the conditioning environ-ment within 24 hours for conditioning andsubsequent weighing. During the period be-tween filter retrieval from the sampler andthe start of the conditioning, the filter shallbe maintained as cool as practical and con-tinuously protected from exposure to tem-peratures over 25 °C. See section 8.3.6 of thisappendix regarding time limits for com-pleting the post-sampling weighing. See ref-erence 2 in section 13.0 of this appendix foradditional guidance on transporting filtersamplers to the conditioning and weighinglaboratory.

10.14. The exposed filter containing thePM2.5 sample shall be re-conditioned in theconditioning environment in accordance


86


with the requirements specified in section 8.2of this appendix.

10.15. The filter shall be reweighed imme-diately after conditioning in accordancewith the requirements specified in section 8.0of this appendix, and the postsamplingweight shall be recorded with the filter iden-tification number.

10.16 The PM2.5 concentration shall be cal-culated as specified in section 12.0 of this ap-pendix.

11.0 Sampler Maintenance. The samplershall be maintained as described by the sam-pler’s manufacturer in the sampler-specificoperation or instruction manual requiredunder section 7.4.18 of this appendix and inaccordance with the specific quality assur-ance program developed and established bythe user based on applicable supplementaryguidance provided in reference 2 in section13.0 of this appendix.

12.0 Calculations12.1 (a) The PM2.5 concentration is cal-

culated as:

PM2.5 = (Wf ¥ Wi)/Va

where:

PM2.5 = mass concentration of PM2.5, µg/m3;Wf, Wi = final and initial weights, respec-

tively, of the filter used to collect thePM2.5 particle sample, µg;

Va = total air volume sampled in actual vol-ume units, as provided by the sampler, m3.

NOTE: Total sample time must be between1,380 and 1,500 minutes (23 and 25 hrs) for afully valid PM2.5 sample; however, see alsosection 3.3 of this appendix.


lution Measurement Systems, Volume I,Principles. EPA/600/R–94/038a, April 1994.Available from CERI, ORD Publications,U.S. Environmental Protection Agency, 26West Martin Luther King Drive, Cincinnati,Ohio 45268.

2. Copies of section 2.12 of the Quality As-surance Handbook for Air Pollution Meas-urement Systems, Volume II, Ambient AirSpecific Methods, EPA/600/R–94/038b, areavailable from Department E (MD-77B), U.S.EPA, Research Triangle Park, NC 27711.

3. Quality Assurance Handbook for Air Pol-lution Measurement Systems, Volume IV:Meteorological Measurements, (Revised Edi-tion) EPA/600/R–94/038d, March, 1995. Avail-able from CERI, ORD Publications, U.S. En-vironmental Protection Agency, 26 WestMartin Luther King Drive, Cincinnati, Ohio45268.

4. Military standard specification (mil.spec.) 8625F, Type II, Class 1 as listed in De-partment of Defense Index of Specificationsand Standards (DODISS), available fromDODSSP–Customer Service, StandardizationDocuments Order Desk, 700 Robbins Avenue,Building 4D, Philadelphia, PA 1911–5094.

14.0 Figures L–1 through L–30 to Appendix L.


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Environmental Protection Agency Pt. 50, App. M

[62 FR 38714, July 18, 1997, as amended at 64FR 19719, Apr. 22, 1999]

APPENDIX M TO PART 50—REFERENCEMETHOD FOR THE DETERMINATION OFPARTICULATE MATTER AS PM10 INTHE ATMOSPHERE

1.0 Applicability.1.1 This method provides for the measure-

ment of the mass concentration of particu-late matter with an aerodynamic diameterless than or equal to a nominal 10 microm-eters (PM1O) in ambient air over a 24-hourperiod for purposes of determining attain-ment and maintenance of the primary andsecondary national ambient air qualitystandards for particulate matter specified in§ 50.6 of this chapter. The measurement proc-ess is nondestructive, and the PM10 samplecan be subjected to subsequent physical orchemical analyses. Quality assurance proce-dures and guidance are provided in part 58,Appendices A and B of this chapter and inreferences 1 and 2 of section 12.0 of this ap-pendix.

2.0 Principle.2.1 An air sampler draws ambient air at a

constant flow rate into a specially shapedinlet where the suspended particulate matteris inertially separated into one or more sizefractions within the PM10 size range. Eachsize fraction in the PM1O size range is thencollected on a separate filter over the speci-fied sampling period. The particle size dis-crimination characteristics (sampling effec-tiveness and 50 percent cutpoint) of the sam-pler inlet are prescribed as performancespecifications in part 53 of this chapter.

2.2 Each filter is weighed (after moistureequilibration) before and after use to deter-mine the net weight (mass) gain due to col-lected PM10. The total volume of air sam-pled, measured at the actual ambient tem-perature and pressure, is determined fromthe measured flow rate and the samplingtime. The mass concentration of PM10 in theambient air is computed as the total mass ofcollected particles in the PM10 size range di-vided by the volume of air sampled, and isexpressed in micrograms per actual cubicmeter (µg/m3).

2.3 A method based on this principle will beconsidered a reference method only if the as-sociated sampler meets the requirementsspecified in this appendix and the require-ments in part 53 of this chapter, and themethod has been designated as a referencemethod in accordance with part 53 of thischapter.

3.0 Range.3.1 The lower limit of the mass concentra-

tion range is determined by the repeatabilityof filter tare weights, assuming the nominalair sample volume for the sampler. For sam-plers having an automatic filter-changingmechanism, there may be no upper limit.

For samplers that do not have an automaticfilter-changing mechanism, the upper limitis determined by the filter mass loading be-yond which the sampler no longer maintainsthe operating flow rate within specified lim-its due to increased pressure drop across theloaded filter. This upper limit cannot bespecified precisely because it is a complexfunction of the ambient particle size dis-tribution and type, humidity, filter type, andperhaps other factors. Nevertheless, all sam-plers should be capable of measuring 24-hourPM10 mass concentrations of at least 300 µg/m3 while maintaining the operating flow ratewithin the specified limits.

4.0 Precision.4.1 The precision of PM10 samplers must be

5 µg/m3 for PM10 concentrations below 80 µg/m3 and 7 percent for PM10 concentrationsabove 80 µg/m3, as required by part 53 of thischapter, which prescribes a test procedurethat determines the variation in the PM10

concentration measurements of identicalsamplers under typical sampling conditions.Continual assessment of precision via collo-cated samplers is required by part 58 of thischapter for PM10 samplers used in certainmonitoring networks.

5.0 Accuracy.5.1 Because the size of the particles making

up ambient particulate matter varies over awide range and the concentration of par-ticles varies with particle size, it is difficultto define the absolute accuracy of PM10 sam-plers. Part 53 of this chapter provides a spec-ification for the sampling effectiveness ofPM10 samplers. This specification requiresthat the expected mass concentration cal-culated for a candidate PM10 sampler, whensampling a specified particle size distribu-tion, be within ±10 percent of that calculatedfor an ideal sampler whose sampling effec-tiveness is explicitly specified. Also, the par-ticle size for 50 percent sampling effective-ness is required to be 10±0.5 micrometers.Other specifications related to accuracyapply to flow measurement and calibration,filter media, analytical (weighing) proce-dures, and artifact. The flow rate accuracy ofPM10 samplers used in certain monitoringnetworks is required by part 58 of this chap-ter to be assessed periodically via flow rateaudits.

6.0 Potential Sources of Error.6.1 Volatile Particles. Volatile particles col-

lected on filters are often lost during ship-ment and/or storage of the filters prior tothe post-sampling weighing 3. Although ship-ment or storage of loaded filters is some-times unavoidable, filters should be re-weighed as soon as practical to minimizethese losses.

6.2 Artifacts. Positive errors in PM10 con-centration measurements may result fromretention of gaseous species on filters 4, 5.Such errors include the retention of sulfurdioxide and nitric acid. Retention of sulfur


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40 CFR Ch. I (7–1–01 Edition)Pt. 50, App. M

dioxide on filters, followed by oxidation tosulfate, is referred to as artifact sulfate for-mation, a phenomenon which increases withincreasing filter alkalinity 6. Little or no ar-tifact sulfate formation should occur usingfilters that meet the alkalinity specificationin section 7.2.4 of this appendix, Artifact ni-trate formation, resulting primarily from re-tention of nitric acid, occurs to varying de-grees on many filter types, including glassfiber, cellulose ester, and many quartz fiberfilters 5, 7, 8, 9, 10. Loss of true atmospheric par-ticulate nitrate during or following samplingmay also occur due to dissociation or chem-ical reaction. This phenomenon has been ob-served on Teflon filters 8 and inferred forquartz fiber filters 11, 12. The magnitude of ni-trate artifact errors in PM10 mass concentra-tion measurements will vary with locationand ambient temperature; however, for mostsampling locations, these errors are expectedto be small.

6.3 Humidity. The effects of ambient humid-ity on the sample are unavoidable. The filterequilibration procedure in section 9.0 of thisappendix is designed to minimize the effectsof moisture on the filter medium.

6.4 Filter Handling. Careful handling of fil-ters between presampling and postsamplingweighings is necessary to avoid errors due todamaged filters or loss of collected particlesfrom the filters. Use of a filter cartridge orcassette may reduce the magnitude of theseerrors. Filters must also meet the integrityspecification in section 7.2.3 of this appendix.

6.5 Flow Rate Variation. Variations in thesampler’s operating flow rate may alter theparticle size discrimination characteristicsof the sampler inlet. The magnitude of thiserror will depend on the sensitivity of theinlet to variations in flow rate and on theparticle distribution in the atmosphere dur-ing the sampling period. The use of a flowcontrol device, under section 7.1.3 of this ap-pendix, is required to minimize this error.

6.6 Air Volume Determination. Errors in theair volume determination may result fromerrors in the flow rate and/or sampling timemeasurements. The flow control deviceserves to minimize errors in the flow rate de-termination, and an elapsed time meter,under section 7.1.5 of this appendix, is re-quired to minimize the error in the samplingtime measurement.

7.0 Apparatus.7.1 PM10 Sampler.7.1.1 The sampler shall be designed to:(a) Draw the air sample into the sampler

inlet and through the particle collection fil-ter at a uniform face velocity.

(b) Hold and seal the filter in a horizontalposition so that sample air is drawn down-ward through the filter.

(c) Allow the filter to be installed and re-moved conveniently.

(d) Protect the filter and sampler from pre-cipitation and prevent insects and other de-bris from being sampled.

(e) Minimize air leaks that would causeerror in the measurement of the air volumepassing through the filter.

(f) Discharge exhaust air at a sufficientdistance from the sampler inlet to minimizethe sampling of exhaust air.

(g) Minimize the collection of dust fromthe supporting surface.

7.1.2 The sampler shall have a sample airinlet system that, when operated within aspecified flow rate range, provides particlesize discrimination characteristics meetingall of the applicable performance specifica-tions prescribed in part 53 of this chapter.The sampler inlet shall show no significantwind direction dependence. The latter re-quirement can generally be satisfied by aninlet shape that is circularly symmetricalabout a vertical axis.

7.1.3 The sampler shall have a flow controldevice capable of maintaining the sampler’soperating flow rate within the flow rate lim-its specified for the sampler inlet over nor-mal variations in line voltage and filter pres-sure drop.

7.1.4 The sampler shall provide a means tomeasure the total flow rate during the sam-pling period. A continuous flow recorder isrecommended but not required. The flowmeasurement device shall be accurate to ±2percent.

7.1.5 A timing/control device capable ofstarting and stopping the sampler shall beused to obtain a sample collection period of24 ±1 hr (1,440 ±60 min). An elapsed timemeter, accurate to within ±15 minutes, shallbe used to measure sampling time. Thismeter is optional for samplers with contin-uous flow recorders if the sampling timemeasurement obtained by means of the re-corder meets the ±15 minute accuracy speci-fication.

7.1.6 The sampler shall have an associatedoperation or instruction manual as requiredby part 53 of this chapter which includes de-tailed instructions on the calibration, oper-ation, and maintenance of the sampler.

7.2 Filters.7.2.1 Filter Medium. No commercially avail-

able filter medium is ideal in all respects forall samplers. The user’s goals in sampling de-termine the relative importance of variousfilter characteristics, e.g., cost, ease of han-dling, physical and chemical characteristics,etc., and, consequently, determine the choiceamong acceptable filters. Furthermore, cer-tain types of filters may not be suitable foruse with some samplers, particularly underheavy loading conditions (high mass con-centrations), because of high or rapid in-crease in the filter flow resistance thatwould exceed the capability of the sampler’sflow control device. However, samplersequipped with automatic filter-changing


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Environmental Protection Agency Pt. 50, App. M

mechanisms may allow use of these types offilters. The specifications given below areminimum requirements to ensure accept-ability of the filter medium for measurementof PM10 mass concentrations. Other filterevaluation criteria should be considered tomeet individual sampling and analysis objec-tives.

7.2.2 Collection Efficiency. ™99 percent, asmeasured by the DOP test (ASTM–2986) with0.3 µm particles at the sampler’s operatingface velocity.

7.2.3 Integrity. ±5 µg/m3 (assuming sampler’snominal 24-hour air sample volume). Integ-rity is measured as the PM10 concentrationequivalent corresponding to the average dif-ference between the initial and the finalweights of a random sample of test filtersthat are weighed and handled under actualor simulated sampling conditions, but haveno air sample passed through them, i.e., fil-ter blanks. As a minimum, the test proce-dure must include initial equilibration andweighing, installation on an inoperativesampler, removal from the sampler, and finalequilibration and weighing.

7.2.4 Alkalinity. <25 microequivalents/gramof filter, as measured by the procedure givenin reference 13 of section 12.0 of this appendixfollowing at least two months storage in aclean environment (free from contaminationby acidic gases) at room temperature and hu-midity.

7.3 Flow Rate Transfer Standard. The flowrate transfer standard must be suitable forthe sampler’s operating flow rate and mustbe calibrated against a primary flow or vol-ume standard that is traceable to the Na-tional Institute of Standard and Technology(NIST). The flow rate transfer standard mustbe capable of measuring the sampler’s oper-ating flow rate with an accuracy of ±2 per-cent.

7.4 Filter Conditioning Environment.7.4.1 Temperature range. 15 to 30 C.7.4.2 Temperature control. ±3 C.7.4.3 Humidity range. 20% to 45% RH.7.4.4 Humidity control. ±5% RH.7.5 Analytical Balance. The analytical bal-

ance must be suitable for weighing the typeand size of filters required by the sampler.The range and sensitivity required will de-pend on the filter tare weights and massloadings. Typically, an analytical balancewith a sensitivity of 0.1 mg is required forhigh volume samplers (flow rates >0.5 m3/min). Lower volume samplers (flow rates <0.5m3/min) will require a more sensitive bal-ance.

8.0 Calibration.8.1 General Requirements.8.1.1 Calibration of the sampler’s flow

measurement device is required to establishtraceability of subsequent flow measure-ments to a primary standard. A flow ratetransfer standard calibrated against a pri-mary flow or volume standard shall be used

to calibrate or verify the accuracy of thesampler’s flow measurement device.

8.1.2 Particle size discrimination by iner-tial separation requires that specific air ve-locities be maintained in the sampler’s airinlet system. Therefore, the flow ratethrough the sampler’s inlet must be main-tained throughout the sampling period with-in the design flow rate range specified by themanufacturer. Design flow rates are speci-fied as actual volumetric flow rates, meas-ured at existing conditions of temperatureand pressure (Qa).

8.2 Flow Rate Calibration Procedure.8.2.1 PM10 samplers employ various types

of flow control and flow measurement de-vices. The specific procedure used for flowrate calibration or verification will vary de-pending on the type of flow controller andflow rate indicator employed. Calibration isin terms of actual volumetric flow rates (Qa)to meet the requirements of section 8.1 ofthis appendix. The general procedure givenhere serves to illustrate the steps involved inthe calibration. Consult the sampler manu-facturer’s instruction manual and reference 2of section 12.0 of this appendix for specificguidance on calibration. Reference 14 of sec-tion 12.0 of this appendix provides additionalinformation on various other measures offlow rate and their interrelationships.

8.2.2 Calibrate the flow rate transfer stand-ard against a primary flow or volume stand-ard traceable to NIST. Establish a calibra-tion relationship, e.g., an equation or familyof curves, such that traceability to the pri-mary standard is accurate to within 2 per-cent over the expected range of ambient con-ditions, i.e., temperatures and pressures,under which the transfer standard will beused. Recalibrate the transfer standard peri-odically.

8.2.3 Following the sampler manufacturer’sinstruction manual, remove the samplerinlet and connect the flow rate transferstandard to the sampler such that the trans-fer standard accurately measures the sam-pler’s flow rate. Make sure there are no leaksbetween the transfer standard and the sam-pler.

8.2.4 Choose a minimum of three flow rates(actual m3/min), spaced over the acceptableflow rate range specified for the inlet, undersection 7.1.2 of the appendix, that can be ob-tained by suitable adjustment of the samplerflow rate. In accordance with the samplermanufacturer’s instruction manual, obtainor verify the calibration relationship be-tween the flow rate (actual m3/min) as indi-cated by the transfer standard and the sam-pler’s flow indicator response. Record theambient temperature and barometric pres-sure. Temperature and pressure correctionsto subsequent flow indicator readings may berequired for certain types of flow measure-ment devices. When such corrections arenecessary, correction on an individual or


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40 CFR Ch. I (7–1–01 Edition)Pt. 50, App. M

daily basis is preferable. However, seasonalaverage temperature and average barometricpressure for the sampling site may be incor-porated into the sampler calibration to avoiddaily corrections. Consult the sampler manu-facturer’s instruction manual and reference 2in section 12.0 of this appendix for additionalguidance.

8.2.5 Following calibration, verify that thesampler is operating at its design flow rate(actual m3/min) with a clean filter in place.

8.2.6 Replace the sampler inlet.9.0 Procedure.9.1 The sampler shall be operated in ac-

cordance with the specific guidance providedin the sampler manufacturer’s instructionmanual and in reference 2 in section 12.0 ofthis appendix. The general procedure givenhere assumes that the sampler’s flow ratecalibration is based on flow rates at ambientconditions (Qa) and serves to illustrate thesteps involved in the operation of a PM10

sampler.9.2 Inspect each filter for pinholes, par-

ticles, and other imperfections. Establish afilter information record and assign an iden-tification number to each filter.

9.3 Equilibrate each filter in the condi-tioning environment (see 7.4) for at least 24hours.

9.4 Following equilibration, weigh each fil-ter and record the presampling weight withthe filter identification number.

9.5 Install a preweighed filter in the sam-pler following the instructions provided inthe sampler manufacturer’s instruction man-ual.

9.6 (a) Turn on the sampler and allow it toestablish run-temperature conditions.Record the flow indicator reading and, ifneeded, the ambient temperature and baro-metric pressure. Determine the sampler flowrate (actual m3/min) in accordance with theinstructions provided in the sampler manu-facturer’s instruction manual.

(b) Note: No onsite temperature or pres-sure measurements are necessary if the sam-pler’s flow indicator does not require tem-perature or pressure corrections or if sea-sonal average temperature and average baro-metric pressure for the sampling site are in-corporated into the sampler calibration,under section 8.2.4 of this appendix. If indi-vidual or daily temperature and pressurecorrections are required, ambient tempera-ture and barometric pressure can be obtainedby on-site measurements or from a nearbyweather station. Barometric pressure read-ings obtained from airports must be stationpressure, not corrected to sea level, and mayneed to be corrected for differences in ele-vation between the sampling site and theairport.

9.7 If the flow rate is outside the accept-able range specified by the manufacturer,check for leaks, and if necessary, adjust the

flow rate to the specified setpoint. Stop thesampler.

9.8 Set the timer to start and stop the sam-pler at appropriate times. Set the elapsedtime meter to zero or record the initialmeter reading.

9.9 Record the sample information (site lo-cation or identification number, sampledate, filter identification number, and sam-pler model and serial number).

9.10 Sample for 24±1 hours.9.11 Determine and record the average flow

rate (Q̄a) in actual m3/min for the samplingperiod in accordance with the instructionsprovided in the sampler manufacturer’s in-struction manual. Record the elapsed timemeter final reading and, if needed, the aver-age ambient temperature and barometricpressure for the sampling period, in note fol-lowing section 9.6 of this appendix.

9.12 Carefully remove the filter from thesampler, following the sampler manufactur-er’s instruction manual. Touch only theouter edges of the filter.

9.13 Place the filter in a protective holderor container, e.g., petri dish, glassine enve-lope, or manila folder.

9.14 Record any factors such as meteoro-logical conditions, construction activity,fires or dust storms, etc., that might be per-tinent to the measurement on the filter in-formation record.

9.15 Transport the exposed sample filter tothe filter conditioning environment as soonas possible for equilibration and subsequentweighing.

9.16 Equilibrate the exposed filter in theconditioning environment for at least 24hours under the same temperature and hu-midity conditions used for presampling filterequilibration (see section 9.3 of this appen-dix).

9.17 Immediately after equilibration, re-weigh the filter and record the postsamplingweight with the filter identification number.

10.0 Sampler Maintenance.10.1 The PM10 sampler shall be maintained

in strict accordance with the maintenanceprocedures specified in the sampler manufac-turer’s instruction manual.

11.0 Calculations.11.1 Calculate the total volume of air sam-

pled as:

V = Qat

where:

V = total air sampled, at ambient tempera-ture and pressure,m3;

Qa = average sample flow rate at ambienttemperature and pressure, m3/min; and

t = sampling time, min.11.2 (a) Calculate the PM10 concentration

as:

PM10 = (Wf¥Wi)×106/V

where:


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Environmental Protection Agency Pt. 50, App. N

PM10 = mass concentration of PM10, µg/m3;Wf, Wi = final and initial weights of filter col-

lecting PM1O particles, g; and106 = conversion of g to µg.

(b) Note: If more than one size fraction inthe PM10 size range is collected by the sam-pler, the sum of the net weight gain by eachcollection filter [Σ(Wf¥Wi)] is used to cal-culate the PM10 mass concentration.


lution Measurement Systems, Volume I,Principles. EPA–600/9–76–005, March 1976.Available from CERI, ORD Publications,U.S. Environmental Protection Agency, 26West St. Clair Street, Cincinnati, OH 45268.

2. Quality Assurance Handbook for Air Pol-lution Measurement Systems, Volume II,Ambient Air Specific Methods. EPA–600/4–77–027a, May 1977. Available from CERI, ORDPublications, U.S. Environmental ProtectionAgency, 26 West St. Clair Street, Cincinnati,OH 45268.

3. Clement, R.E., and F.W. Karasek. Sam-ple Composition Changes in Sampling andAnalysis of Organic Compounds in Aerosols.Int. J. Environ. Analyt. Chem., 7:109, 1979.

4. Lee, R.E., Jr., and J. Wagman. A Sam-pling Anomaly in the Determination of At-mospheric Sulfate Concentration. Amer. Ind.Hyg. Assoc. J., 27:266, 1966.

5. Appel, B.R., S.M. Wall, Y. Tokiwa, andM. Haik. Interference Effects in SamplingParticulate Nitrate in Ambient Air. Atmos.Environ., 13:319, 1979.

6. Coutant, R.W. Effect of EnvironmentalVariables on Collection of Atmospheric Sul-fate. Environ. Sci. Technol., 11:873,1977.Spicer, C.W., and P. Schumacher. Inter-ference in Sampling Atmospheric Particu-late Nitrate. Atmos. Environ., 11:873, 1977.

8. Appel, B.R., Y. Tokiwa, and M. Haik.Sampling of Nitrates in Ambient Air. Atmos.Environ., 15:283, 1981.

9. Spicer, C.W., and P.M. Schumacher. Par-ticulate Nitrate: Laboratory and Field Stud-ies of Major Sampling Interferences. Atmos.Environ., 13:543, 1979.

10. Appel, B.R. Letter to Larry Purdue,U.S. EPA, Environmental Monitoring andSupport Laboratory. March 18, 1982, DocketNo. A–82–37, II–I–1.

11. Pierson, W.R., W.W. Brachaczek, T.J.Korniski, T.J. Truex, and J.W. Butler. Arti-fact Formation of Sulfate, Nitrate, and Hy-drogen Ion on Backup Filters: AlleghenyMountain Experiment. J. Air Pollut. ControlAssoc., 30:30, 1980.

12. Dunwoody, C.L. Rapid Nitrate LossFrom PM10 Filters. J. Air Pollut. ControlAssoc., 36:817, 1986.

13. Harrell, R.M. Measuring the Alkalinityof Hi-Vol Air Filters. EMSL/RTP–SOP–QAD–534, October 1985. Available from the U.S. En-vironmental Protection Agency, EMSL/QAD,Research Triangle Park, NC 27711.

14. Smith, F., P.S. Wohlschlegel, R.S.C.Rogers, and D.J. Mulligan. Investigation ofFlow Rate Calibration Procedures Associ-ated With the High Volume Method for De-termination of Suspended Particulates.EPA–600/4–78–047, U.S. Environmental Pro-tection Agency, Research Triangle Park, NC27711, 1978.

[62 FR 38753, July 18, 1997]

APPENDIX N TO PART 50—INTERPRETA-TION OF THE NATIONAL AMBIENT AIRQUALITY STANDARDS FOR PARTICU-LATE MATTER

1.0 General.(a) This appendix explains the data han-

dling conventions and computations nec-essary for determining when the annual and24-hour primary and secondary national am-bient air quality standards for PM specifiedin § 50.7 of this chapter are met. Particulatematter is measured in the ambient air asPM10 and PM2.5 (particles with an aero-dynamic diameter less than or equal to anominal 10 and 2.5 micrometers, respec-tively) by a reference method based on ap-pendix M of this part for PM10 and on appen-dix L of this part for PM2.5, as applicable, anddesignated in accordance with part 53 of thischapter, or by an equivalent method des-ignated in accordance with part 53 of thischapter. Data handling and computation pro-cedures to be used in making comparisonsbetween reported PM10 and PM2.5 concentra-tions and the levels of the PM standards arespecified in the following sections.

(b) Data resulting from uncontrollable ornatural events, for example structural firesor high winds, may require special consider-ation. In some cases, it may be appropriateto exclude these data because they could re-sult in inappropriate values to compare withthe levels of the PM standards. In othercases, it may be more appropriate to retainthe data for comparison with the level of thePM standards and then allow the EPA to for-mulate the appropriate regulatory response.Whether to exclude, retain, or make adjust-ments to the data affected by uncontrollableor natural events is subject to the approvalof the appropriate Regional Administrator.

(c) The terms used in this appendix are de-fined as follows:

Average and mean refer to an arithmeticmean.

Daily value for PM refers to the 24-hour av-erage concentration of PM calculated ormeasured from midnight to midnight (localtime) for PM10 or PM2.5.

Designated monitors are those monitoringsites designated in a State PM MonitoringNetwork Description for spatial averaging inareas opting for spatial averaging in accord-ance with part 58 of this chapter.


122

40 CFR Ch. I (7–1–01 Edition)Pt. 50, App. N

98th percentile (used for PM2.5) means thedaily value out of a year of monitoring databelow which 98 percent of all values in thegroup fall.

99th percentile (used for PM10) means thedaily value out of a year of monitoring databelow which 99 percent of all values in thegroup fall.

Year refers to a calendar year.(d) Sections 2.1 and 2.5 of this appendix

contain data handling instructions for theoption of using a spatially averaged networkof monitors for the annual standard. If spa-tial averaging is not considered for an area,then the spatial average is equivalent to theannual average of a single site and is treatedaccordingly in subsequent calculations. Forexample, paragraph (a)(3) of section 2.1 ofthis appendix could be eliminated since thespatial average would be equivalent to theannual average.

2.0 Comparisons with the PM2.5 Standards.2.1 Annual PM2.5 Standard.(a) The annual PM2.5 standard is met when

the 3-year average of the spatially averagedannual means is less than or equal to 15.0 µg/m3. The 3-year average of the spatially aver-aged annual means is determined by aver-aging quarterly means at each monitor toobtain the annual mean PM2.5 concentrationsat each monitor, then averaging across alldesignated monitors, and finally averagingfor 3 consecutive years. The steps can besummarized as follows:

(1) Average 24-hour measurements to ob-tain quarterly means at each monitor.

(2) Average quarterly means to obtain an-nual means at each monitor.

(3) Average across designated monitoringsites to obtain an annual spatial mean for anarea (this can be one site in which case thespatial mean is equal to the annual mean).

(4) Average 3 years of annual spatial meansto obtain a 3-year average of spatially aver-aged annual means.

(b) In the case of spatial averaging, 3 yearsof spatial averages are required to dem-onstrate that the standard has been met.Designated sites with less than 3 years ofdata shall be included in spatial averages forthose years that data completeness require-ments are met. For the annual PM2.5 stand-ard, a year meets data completeness require-ments when at least 75 percent of the sched-uled sampling days for each quarter havevalid data. However, years with high con-centrations and more than a minimalamount of data (at least 11 samples in eachquarter) shall not be ignored just becausethey are comprised of quarters with lessthan complete data. Thus, in computing an-nual spatially averaged means, years con-taining quarters with at least 11 samples butless than 75 percent data completeness shallbe included in the computation if the result-ing spatially averaged annual mean con-centration (rounded according to the conven-

tions of section 2.3 of this appendix) is great-er than the level of the standard.

(c) Situations may arise in which there arecompelling reasons to retain years con-taining quarters which do not meet the datacompleteness requirement of 75 percent orthe minimum number of 11 samples. The useof less than complete data is subject to theapproval of the appropriate Regional Admin-istrator.

(d) The equations for calculating the 3-yearaverage annual mean of the PM2.5 standardare given in section 2.5 of this appendix.

2.2 24-Hour PM2.5 Standard.(a) The 24-hour PM2.5 standard is met when

the 3-year average of the 98th percentile val-ues at each monitoring site is less than orequal to 65 µg/m3. This comparison shall bebased on 3 consecutive, complete years of airquality data. A year meets data complete-ness requirements when at least 75 percent ofthe scheduled sampling days for each quarterhave valid data. However, years with highconcentrations shall not be ignored just be-cause they are comprised of quarters withless than complete data. Thus, in computingthe 3-year average 98th percentile value, yearscontaining quarters with less than 75 percentdata completeness shall be included in thecomputation if the annual 98th percentilevalue (rounded according to the conventionsof section 2.3 of this appendix) is greaterthan the level of the standard.

(b) Situations may arise in which there arecompelling reasons to retain years con-taining quarters which do not meet the datacompleteness requirement. The use of lessthan complete data is subject to the ap-proval of the appropriate Regional Adminis-trator.

(c) The equations for calculating the 3-yearaverage of the annual 98th percentile values isgiven in section 2.6 of this appendix.

2.3 Rounding Conventions. For the purposesof comparing calculated values to the appli-cable level of the standard, it is necessary toround the final results of the calculations de-scribed in sections 2.5 and 2.6 of this appen-dix. For the annual PM2.5 standard, the 3-year average of the spatially averaged an-nual means shall be rounded to the nearest0.1 µg/m3 (decimals 0.05 and greater arerounded up to the next 0.1, and any decimallower than 0.05 is rounded down to the near-est 0.1). For the 24-hour PM2.5 standard, the3-year average of the annual 98th percentilevalues shall be rounded to the nearest 1 µg/m3 (decimals 0.5 and greater are rounded upto nearest whole number, and any decimallower than 0.5 is rounded down to the nearestwhole number).

2.4 Monitoring Considerations.(a) Section 58.13 of this chapter specifies

the required minimum frequency of sampling


123


for PM2.5. Exceptions to the specified sam-pling frequencies, such as a reduced fre-quency during a season of expected low con-centrations, are subject to the approval ofthe appropriate Regional Administrator.Section 58.14 of 40 CFR part 58 and section 2.8of appendix D of 40 CFR part 58, specifywhich monitors are eligible for making com-parisons with the PM standards. In deter-mining a spatial mean using two or moremonitoring sites operating in a given year,the annual mean for an individual site maybe included in the spatial mean if and only ifthe mean for that site meets the criterionspecified in § 2.8 of appendix D of 40 CFR part58. In the event data from an otherwise eligi-ble site is excluded from being averaged withdata from other sites on the basis of this cri-terion, then the 3-year mean from that siteshall be compared directly to the annualstandard.

(b) For the annual PM2.5 standard, whendesignated monitors are located at the samesite and are reporting PM2.5 values for thesame time periods, and when spatial aver-aging has been chosen, their concentrationsshall be averaged before an area-wide spatialaverage is calculated. Such monitors willthen be considered as one monitor.

2.5 Equations for the Annual PM2.5 Standard.(a) An annual mean value for PM2.5 is de-

termined by first averaging the daily valuesof a calendar quarter:

Equation 1

xn

xq y sq

i q y si

nq

, , , , ,==∑1

1

where:x̄q,y,s = the mean for quarter q of year y for

site s;nq = the number of monitored values in the

quarter; andxi,q,y,s = the ith value in quarter q for year y

for site s.

(b) The following equation is then to beused for calculation of the annual mean:

Equation 2

x xy s q y sq

, , ,==∑1

4 1

4

where:x̄y,s = the annual mean concentration for year

y (y = 1, 2, or 3) and for site s; andx̄q,y,s = the mean for quarter q of year y for

site s.

(c)(1) The spatially averaged annual meanfor year y is computed by first calculatingthe annual mean for each site designated tobe included in a spatial average, x̄y,s, and

then computing the average of these valuesacross sites:

Equation 3

xn

xys

y ss

ns

==∑1

1,

where:

x̄y = the spatially averaged mean for year y;x̄y,s = the annual mean for year y and site s;

andns = the number of sites designated to be

averaged.

(2) In the event that an area designated forspatial averaging has two or more sites atthe same location producing data for thesame time periods, the sites are averaged to-gether before using Equation 3 by:

Equation 4

xn

xy s*c

y ss

nc

, ,==∑1

1where:

x̄y,s* = the annual mean for year y for thesites at the same location (which will nowbe considered one site);

nc = the number of sites at the same locationdesignated to be included in the spatial av-erage; and

x̄y,s = the annual mean for year y and site s.

(d) The 3-year average of the spatiallyaveraged annual means is calculated byusing the following equation:

Equation 5

x xyy

==∑1

3 1

3

where:

x̄ = the 3-year average of the spatially aver-aged annual means; and

x̄y = the spatially averaged annual mean foryear y.

Example 1—Area Designated for Spatial Aver-aging That Meets the Primary Annual PM2.5

Standard.

a. In an area designated for spatial aver-aging, four designated monitors recordeddata in at least 1 year of a particular 3-yearperiod. Using Equations 1 and 2, the annualmeans for PM2.5 at each site are calculatedfor each year. The following table can be cre-ated from the results. Data completenesspercentages for the quarter with the fewestnumber of samples are also shown.


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TABLE 1—RESULTS FROM EQUATIONS 1 AND 2

Site ⊥ 1 Site ⊥ 2 Site ⊥ 3 Site ⊥ 4 Spatial mean

Year 1 ................... Annual mean (µg/m3) ....... 12.7 ...................... ...................... ...................... 12.7% data completeness ....... 80 0 0 0 ......................

Year 2 ................... Annual mean (µg/m3) ....... 12.6 17.5 15.2 ...................... 15.05% data completeness ....... 90 63 38 0 ......................

Year 3 ................... Annual mean (µg/m3) ....... 12.5 18.5 14.1 16.9 15.50% data completeness ....... 90 80 85 50 ......................

3-year mean ......... ........................................... ...................... ...................... ...................... ...................... 14.42

b. The data from these sites are averagedin the order described in section 2.1 of thisappendix. Note that the annual mean fromsite #3 in year 2 and the annual mean fromsite #4 in year 3 do not meet the 75 percentdata completeness criteria. Assuming the 38percent data completeness represents a quar-ter with fewer than 11 samples, site #3 inyear 2 does not meet the minimum data com-pleteness requirement of 11 samples in eachquarter. The site is therefore excluded fromthe calculation of the spatial mean for year2. However, since the spatial mean for year 3is above the level of the standard and theminimum data requirement of 11 samples ineach quarter has been met, the annual meanfrom site #4 in year 3 is included in the cal-

culation of the spatial mean for year 3 and inthe calculation of the 3-year average. The 3-year average is rounded to 14.4 µg/m3, indi-cating that this area meets the annual PM2.5

standard.

Example 2—Area With Two Monitors at theSame Location That Meets the Primary An-nual PM2.5 Standard.

a. In an area designated for spatial aver-aging, six designated monitors, with twomonitors at the same location (#5 and #6),recorded data in a particular 3-year period.Using Equations 1 and 2, the annual meansfor PM2.5 are calculated for each year. Thefollowing table can be created from the re-sults.

TABLE 2—RESULTS FROM EQUATIONS 1 AND 2

Annualmean (µg/

m3)Site ⊥ 1 Site ⊥ 2 Site ⊥ 3 Site ⊥ 4 Site ⊥ 5 Site ⊥ 6 Average of

⊥ 5 and ⊥ 6Spatialmean

Year 1 ....... 12.9 9.9 12.6 11.1 14.5 14.6 14.55 12.21Year 2 ....... 14.5 13.3 12.2 10.9 16.1 16.0 16.05 13.39Year 3 ....... 14.4 12.4 11.5 9.7 12.3 12.1 12.20 12.043-Year

mean ...... .................... .................... .................... .................... .................... .................... .................. 12.55

b. The annual means for sites #5 and #6 areaveraged together using Equation 4 beforethe spatial average is calculated using Equa-tion 3 since they are in the same location.The 3-year mean is rounded to 12.6 µg/m3, in-dicating that this area meets the annualPM2.5 standard.

Example 3—Area With a Single Monitor ThatMeets the Primary Annual PM2.5 Standard.

a. Given data from a single monitor in anarea, the calculations are as follows. UsingEquations 1 and 2, the annual means forPM2.5 are calculated for each year. If the an-nual means are 10.28, 17.38, and 12.25 µg/m3,then the 3-year mean is:

x g m= × =(1 / 3) (10.28 +17.38 +12.25) 13.303 µ / .3

b. This value is rounded to 13.3, indicatingthat this area meets the annual PM2.5 stand-ard.

2.6 Equations for the 24-Hour PM2.5 Standard.(a) When the data for a particular site and

year meet the data completeness require-ments in section 2.2 of this appendix, cal-culation of the 98th percentile is accom-

plished by the following steps. All the dailyvalues from a particular site and year com-prise a series of values (x1, x2, x3, ..., xn), thatcan be sorted into a series where each num-ber is equal to or larger than the precedingnumber (x[1], x[2], x[3], ..., x[n]). In this case, x[1]

is the smallest number and x[n] is the largestvalue. The 98th percentile is found from the


125


sorted series of daily values which is orderedfrom the lowest to the highest number. Com-pute (0.98) × (n) as the number ‘‘i.d’’, where‘‘i’’ is the integer part of the result and ‘‘d’’is the decimal part of the result. The 98th per-centile value for year y, P0.98, y, is given byEquation 6:

Equation 6

P Xy i0 98 1. , = +[ ]where:

P0.98,y = 98th percentile for year y;x[i=1] = the (i=1)th number in the ordered series

of numbers; andi = the integer part of the product of 0.98 and

n.

(b) The 3-year average 98th percentile isthen calculated by averaging the annual 98th

percentiles:

Equation 7

P

P yy

0 98

0 981

3

3.

. ,

= =∑

(c) The 3-year average 98th percentile isrounded according to the conventions in sec-tion 2.3 of this appendix before a comparisonwith the standard is made.

Example 4—Ambient Monitoring Site WithEvery-Day Sampling That Meets the Primary24-Hour PM2.5 Standard.

a. In each year of a particular 3 year pe-riod, varying numbers of daily PM2.5 values(e.g., 281, 304, and 296) out of a possible 365values were recorded at a particular sitewith the following ranked values (in µg/m3):

TABLE 3—ORDERED MONITORING DATA FOR 3 YEARS

Year 1 Year 2 Year 3

j rank Xj value j rank Xj value j rank Xj value

275 57.9 296 54.3 290 66.0276 59.0 297 57.1 291 68.4277 62.2 298 63.0 292 69.8

b. Using Equation 6, the 98th percentile val-ues for each year are calculated as follows:

0 98 281 1 276 59 00 98 1 2763. . /. , 275.38× = ⇒ + = ⇒ = =[ ]i P X g mµ

0 98 304 1 298 63 00 98 2 2983. . /. , 297.92× = ⇒ + = ⇒ = =[ ]i P X g mµ

0 98 296 1 291 680 98 3 2913. .4 /. , 290.07× = ⇒ + = ⇒ = =[ ]i P X g mµ

c.1. Using Equation 7, the 3-year average98th percentile is calculated as follows:

P g m g m0 983 359 0 63 0 68

363.

. . .4.46 / /= + + = µ µ, which rounds to 63 .

2. Therefore, this site meets the 24-hourPM2.5 standard.

3.0 Comparisons with the PM10 Standards.3.1 Annual PM10 Standard.(a) The annual PM10 standard is met when

the 3-year average of the annual mean PM10

concentrations at each monitoring site isless than or equal to 50 µg/m3. The 3-year av-

erage of the annual means is determined byaveraging quarterly means to obtain annualmean PM10 concentrations for 3 consecutive,complete years at each monitoring site. Thesteps can be summarized as follows:

(1) Average 24-hour measurements to ob-tain a quarterly mean.


126


(2) Average quarterly means to obtain anannual mean.

(3) Average annual means to obtain a 3-year mean.

(b) For the annual PM10 standard, a yearmeets data completeness requirements whenat least 75 percent of the scheduled samplingdays for each quarter have valid data. How-ever, years with high concentrations andmore than a minimal amount of data (atleast 11 samples in each quarter) shall not beignored just because they are comprised ofquarters with less than complete data. Thus,in computing the 3-year average annualmean concentration, years containing quar-ters with at least 11 samples but less than 75percent data completeness shall be includedin the computation if the annual mean con-centration (rounded according to the conven-tions of section 2.3 of this appendix) is great-er than the level of the standard.

(c) Situations may arise in which there arecompelling reasons to retain years con-taining quarters which do not meet the datacompleteness requirement of 75 percent orthe minimum number of 11 samples. The useof less than complete data is subject to theapproval of the appropriate Regional Admin-istrator.

(d) The equations for calculating the 3-yearaverage annual mean of the PM10 standardare given in section 3.5 of this appendix.

3.2 24-Hour PM10 Standard.(a) The 24-hour PM10 standard is met when

the 3-year average of the annual 99th per-centile values at each monitoring site is lessthan or equal to 150 µg/m3. This comparisonshall be based on 3 consecutive, completeyears of air quality data. A year meets datacompleteness requirements when at least 75percent of the scheduled sampling days foreach quarter have valid data. However, yearswith high concentrations shall not be ig-nored just because they are comprised ofquarters with less than complete data. Thus,in computing the 3-year average of the an-nual 99th percentile values, years containingquarters with less than 75 percent data com-pleteness shall be included in the computa-tion if the annual 99th percentile value(rounded according to the conventions of sec-tion 2.3 of this appendix) is greater than thelevel of the standard.

(b) Situations may arise in which there arecompelling reasons to retain years con-taining quarters which do not meet the datacompleteness requirement. The use of lessthan complete data is subject to the ap-proval of the appropriate Regional Adminis-trator.

(c) The equation for calculating the 3-yearaverage of the annual 99th percentile values isgiven in section 2.6 of this appendix.

3.3 Rounding Conventions. For the annualPM10 standard, the 3-year average of the an-nual PM10 means shall be rounded to thenearest 1 µg/m3 (decimals 0.5 and greater are

rounded up to the next whole number, andany decimal less than 0.5 is rounded down tothe nearest whole number). For the 24-hourPM10 standard, the 3-year average of the an-nual 99th percentile values of PM10 shall berounded to the nearest 10 µg/m3 (155 µg/m3

and greater would be rounded to 160 µg/m3

and 154 µg/m3 and less would be rounded to150 µg/m3).

3.4 Monitoring Considerations. Section 58.13of this chapter specifies the required min-imum frequency of sampling for PM10. Ex-ceptions to the specified sampling fre-quencies, such as a reduced frequency duringa season of expected low concentrations, aresubject to the approval of the appropriateRegional Administrator. For making com-parisons with the PM10 NAAQS, all sitesmeeting applicable requirements in part 58of this chapter would be used.

3.5 Equations for the Annual PM10 Standard.(a) An annual arithmetic mean value for

PM10 is determined by first averaging the 24-hour values of a calendar quarter using thefollowing equation:

Equation 8

xn

xq yq

i q yi

nq

, , ,==∑1

1

where:x̄q,y = the mean for quarter q of year y;nq = the number of monitored values in the

quarter; andxi,q,y = the ith value in quarter q for year y.

(b) The following equation is then to beused for calculation of the annual mean:

Equation 9

x xy q yq

==∑1

4 1

4

,

where:x̄y = the annual mean concentration for year

y, (y=1, 2, or 3); andxq,y = the mean for a quarter q of year y.

(c) The 3-year average of the annual meansis calculated by using the following equa-tion:

Equation 10

x xyy

==∑1

3 1

3

where:x̄ = the 3-year average of the annual means;

and

x̄y = the annual mean for calendar year y.


127


Example 5—Ambient Monitoring Site That DoesNot Meet the Annual PM10 Standard.

a. Given data from a PM10 monitor andusing Equations 8 and 9, the annual means

for PM10 are calculated for each year. If theannual means are 52.42, 82.17, and 63.23 µg/m3,then the 3-year average annual mean is:

x g m= × + + =(1 / 3) (52.42 82.17 63.23) 65.94, which is rounded to 66 µ / .3

b. Therefore, this site does not meet theannual PM10 standard.

3.6 Equation for the 24-Hour PM10 Standard.(a) When the data for a particular site and

year meet the data completeness require-ments in section 3.2 of this appendix, cal-culation of the 99th percentile is accom-plished by the following steps. All the dailyvalues from a particular site and year com-prise a series of values (x1, x2, x3, ..., xn) thatcan be sorted into a series where each num-ber is equal to or larger than the precedingnumber (x[1], x[2], x[3], ..., x[n]). In this case, x[1]

is the smallest number and x[n] is the larg-est value. The 99th percentile is found fromthe sorted series of daily values which is or-dered from the lowest to the highest number.Compute (0.99) × (n) as the number ‘‘i.d’’,where ‘‘i’’ is the integer part of the resultand ‘‘d’’ is the decimal part of the result.The 99th percentile value for year y, P0.99,y, isgiven by Equation 11:

Equation 11

P Xy i0 99 1. , = +[ ]where:

P0.99,y = the 99th percentile for year y;

x[i=1] = the (i=1)th number in the ordered seriesof numbers; and

i = the integer part of the product of 0.99 andn.

(b) The 3-year average 99th percentile valueis then calculated by averaging the annual99th percentiles:

Equation 12

P

P yy

0 99

0 991

3

3.

. ,

= =∑

(c) The 3-year average 99th percentile isrounded according to the conventions in sec-tion 3.3 of this appendix before a comparisonwith the standard is made.

Example 6—Ambient Monitoring Site With Sam-pling Every Sixth Day That Meets the Pri-mary 24-Hour PM10 Standard.

a. In each year of a particular 3 year pe-riod, varying numbers of PM10 daily values(e.g., 110, 98, and 100) out of a possible 121daily values were recorded at a particularsite with the following ranked values (in µg/m3):

TABLE 4—ORDERED MONITORING DATA FOR 3 YEARS

Year 1 Year 2 Year 3

j rank Xj value j rank Xj value j rank Xj value

108 120 96 143 98 140109 128 97 148 99 144110 130 98 150 100 147

b. Using Equation 11, the 99th percentilevalues for each year are calculated as fol-lows:

0 99 1 109 1280 99 1 1093. /. , 110 = 108.9 × ⇒ + = ⇒ = =[ ]i P X g mµ

0 99 1 98 1500 99 2 983. /. , 98 = 97.02 × ⇒ + = ⇒ = =[ ]i P X g mµ


128

40 CFR Ch. I (7–1–01 Edition)Pt. 51

0 99 1 100 1470 99 3 1003. /. , 100 = 99× ⇒ + = ⇒ = =[ ]i P X g mµ

c. 1. Using Equation 12, the 3-year average99th percentile is calculated as follows:

128 50 147

3141 7 1403 3+ + = . / / rounds to .µ µg m g m

2. Therefore, this site meets the 24-hourPM10 standard.

[62 FR 38755, July 18, 1997]

PART 51—REQUIREMENTS FORPREPARATION, ADOPTION, ANDSUBMITTAL OF IMPLEMENTATIONPLANS

Subparts A–E [Reserved]

Subpart F—Procedural Requirements

Sec.51.100 Definitions.51.101 Stipulations.51.102 Public hearings.51.103 Submission of plans, preliminary re-

view of plans.51.104 Revisions.51.105 Approval of plans.

Subpart G—Control Strategy

51.110 Attainment and maintenance of na-tional standards.

51.111 Description of control measures.51.112 Demonstration of adequacy.51.113 [Reserved]51.114 Emissions data and projections.51.115 Air quality data and projections.51.116 Data availability.51.117 Additional provisions for lead.51.118 Stack height provisions.51.119 Intermittent control systems.51.120 Requirements for State Implementa-

tion Plan revisions relating to newmotor vehicles.

51.121 Findings and requirements for sub-mission of State implementation plan re-visions relating to emissions of oxides ofnitrogen.

51.122 Emissions reporting requirements forSIP revisions relating to budgets for NOX

emissions.

Subpart H—Prevention of Air PollutionEmergency Episodes

51.150 Classification of regions for episodeplans.

51.151 Significant harm levels.51.152 Contingency plans.51.153 Reevaluation of episode plans.

Subpart I—Review of New Sources andModifications

51.160 Legally enforceable procedures.51.161 Public availability of information.51.162 Identification of responsible agency.51.163 Administrative procedures.51.164 Stack height procedures.51.165 Permit requirements.51.166 Prevention of significant deteriora-

tion of air quality.

Subpart J—Ambient Air QualitySurveillance

51.190 Ambient air quality monitoring re-quirements.

Subpart K—Source Survelliance

51.210 General.51.211 Emission reports and recordkeeping.51.212 Testing, inspection, enforcement, and

complaints.51.213 Transportation control measures.51.214 Continuous emission monitoring.

Subpart L—Legal Authority

51.230 Requirements for all plans.51.231 Identification of legal authority.51.232 Assignment of legal authority to

local agencies.

Subpart M—IntergovernmentalConsultation

AGENCY DESIGNATION

51.240 General plan requirements.51.241 Nonattainment areas for carbon mon-

oxide and ozone.51.242 [Reserved]
