Approval Standard

for Combustible Open Path

Gas Monitors

Class Number 6325

December 2005

2005 FM Approvals LLC. All rights reserved.

Foreword

The FM Approvals certification mark is intended to verify that the products and services described will meet FM Approvals stated conditions of performance, safety and quality useful to the ends of property conservation. The purpose of Approval Standards is to present the criteria for FM Approval of various types of products and services, as guidance for FM Approvals personnel, manufacturers, users and authorities having jurisdiction.

Products submitted for certification by FM Approvals shall demonstrate that they meet the intent of the Approval Standard, and that quality control in manufacturing shall ensure a consistently uniform and reliable product. Approval Standards strive to be performance-oriented. They are intended to facilitate technological development.

For examining equipment, materials and services, Approval Standards:

a) must be useful to the ends of property conservation by preventing, limiting or not

causing damage under the conditions stated by the Approval listing; and

b) must be readily identifiable.

Continuance of Approval and listing depends on compliance with the Approval Agreement, satisfactory performance in the field, on successful re-examinations of equipment, materials, and services as appropriate, and on periodic follow-up audits of the manufacturing facility.

FM Approvals LLC reserves the right in its sole judgment to change or revise its standards, criteria, methods, or procedures.

TABLE OF CONTENTS

1. SCOPE ......................................................................................................................................................................................... 1

2. DEFINITIONS ............................................................................................................................................................................ 1

3. GENERAL REQUIREMENTS ............................................................................................................................................... 43.1 Review of Documentation .................................................................................................................................................. 43.2 Markings ............................................................................................................................................................................ 53.3 Manufacturers Installation and Operation Manuals ........................................................................................................ 53.4 Construction and Functions .............................................................................................................................................. 83.5 Test Equipment Calibration .............................................................................................................................................. 10

4. PERFORMANCE REQUIREMENTS ................................................................................................................................. 104.1 General .............................................................................................................................................................................. 104.2 Samples and Sequence ..................................................................................................................................................... 114.3 Preparation of Apparatus .................................................................................................................................................. 114.4 Conditions for Test and Test Area .................................................................................................................................. 114.5 Un-Powered Preconditioning Storage .............................................................................................................................. 154.6 Vibration ........................................................................................................................................................................... 154.7 Calibration ......................................................................................................................................................................... 154.8 Accuracy .......................................................................................................................................................................... 164.9 Trouble Signals ................................................................................................................................................................. 164.10 Temperature .................................................................................................................................................................... 174.11 Time of Response ........................................................................................................................................................... 184.12 Solar Radiation ............................................................................................................................................................... 194.13 Power Supply Variations ................................................................................................................................................ 194.14 Power Supply Interruptions and Transients ................................................................................................................... 204.15 Recovery from Power Supply Interruption ................................................................................................................... 204.16 Electromagnetic Interference (EMI) .............................................................................................................................. 214.17 Partial Obscuration ......................................................................................................................................................... 214.18 Simulated Fog/Mist (Intended for Outdoor Use) .......................................................................................................... 214.19 Water Vapor Interference .............................................................................................................................................. 214.20 Beam Blockage Fault .................................................................................................................................................... 224.21 Long Range Operation ................................................................................................................................................... 224.22 Environmental Ratings ................................................................................................................................................... 224.23 Long Term Stability ...................................................................................................................................................... 23

5. OPERATIONS REQUIREMENTS ....................................................................................................................................... 235.1 Demonstrated Quality Control Program .......................................................................................................................... 235.2 Facilities and Procedures Audit ...................................................................................................................................... 245.3 Installation Inspections ..................................................................................................................................................... 245.4 Manufacturers Responsibilities ....................................................................................................................................... 24

APPENDIX A: Open Path Monitor Figures ............................................................................................................................. 25

APPENDIX B: Units of Measurement ...................................................................................................................................... 26

1. SCOPE1.1 This standard provides minimum requirements of open path gas monitoring apparatus.

1.2 This standard is concerned with the details of construction, performance and testing of open path (line-of-sight) gas monitors that sense the presence of combustible gas or vapor concentrations in air. Based onassociated requirements, this standard considers the suitability of the apparatus, or parts thereof, for use inClass I, hazardous (classified) locations as defined by the National Electrical Code (ANSI/NFPA 70).

1.3 For apparatus used for sensing the presence of multiple gases, non-flammable toxic gases, as well as a gasthat is both toxic and combustible, this document applies only to the portion sensing the presence offlammable gas or vapor.

1.4 This standard addresses combustible gas monitors intended to provide a broad indication or alarm, thepurpose of which is to give warning of possible presence of a potential flammable concentration of gas orvapor.

1.5 This standard does not address gas monitoring or monitoring apparatus of the laboratory or scientific typeused for analysis or measurement, apparatus used for process control and process monitoring purposes, orapparatus used for residential purposes.

1.6 This standard is written for gas monitoring apparatus that are intended to monitor gases or vapors in ambientair by measuring the spectral absorption by the gases or vapors over an extended optical path. The units ofmeasurement and range of the gas monitoring apparatus are a mathematical integral of the gas concentrationalong the optical path. The units of measurement are expressed as full concentration of the lower flammablelimit (100%LFL or 1LFL) multiplied by the distance, in meters, at that concentration (e.g., LFL meter,%LFL(Avg)).

1.7 The standard is limited to instrument applications where: calibration is performed using either the gas to bemonitored or another gas for which response conversion data appears in the instruction manual.

NOTE: FOR CONVENIENCE, THE SHORTER TERM GAS MAY BE USED AS AN ABBREVIATION FOR COMBUSTIBLE GASOR VAPOR WITHIN THIS DOCUMENT.

2. DEFINITIONSFor purposes of this standard, the following terms apply:

2.1 Alarm: An audible, visual or physical presentation designed to alert the apparatus user that a specificmeasurement level has been reached or exceeded.

2.1.1 Alarm Set Point: a fixed or adjustable setting of the system that is intended to pre-set the value ofintegral concentration at which the apparatus will automatically initiate an indication, alarm, or otheroutput function for the selected gas concentration level(s) at which an indication, alarm, or otheroutput function is initiated.

2.1.2 alarm signal: an audible, visual, electronic or other signal generated by the apparatus when anintegral concentration of gas in excess of a preset value is detected.

2.1.3 latching alarm: an alarm which, once activated, requires a deliberate action to deactivate it.

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2.2 Alarm only apparatus: an apparatus having an alarm but not having a meter or other indicating device thatwould allow measurement of the deviations permitted by the requirements of this standard.

2.3 Calibration: the act of adjusting an apparatus to zero and setting the desired span.

2.4 Calibration gas concentration: the concentration of the combustible gas in ambient air used to set theapparatus span or alarm set point.

2.5 Clean air: air that is free of combustible gases, vapors or contaminating substances.

2.6 Combustible gas: any flammable gas or vapor that, in sufficient concentration by volume in air which canbecome the fuel for an explosion or fire hazard.

2.7 Control unit: that portion of a gas monitoring apparatus that is not directly responsive to the combustiblegas, but which responds to the electrical signal obtained from one or more detector heads and produces anindication, alarm or other output function.

2.8 Diffusion: a method by which an atmosphere being monitored gains access to the gas sensing element bynature of molecular movement or natural convection.

2.9 Explosion protection: the measures applied in the construction of electrical apparatus to prevent ignitionof a surrounding combustible atmosphere by the apparatus

2.10 Fixed apparatus: an apparatus which is intended to have all its parts permanently installed

2.11 Flammable range: the range of flammable vapor concentrations or gas-air mixtures in which propagationof flame will occur on contact with a source of ignition.

NOTE 1: THE TERMS LOWER FLAMMABLE LIMIT (LFL) AND LOWER EXPLOSIVE LIMIT (LEL) ARE DEEMED TO BESYNONYMOUS. THE TERMS UPPER FLAMMABLE LIMIT (UFL)AND UPPER EXPLOSIVE LIMIT (UEL)AREDEEMED TO BE SYNONYMOUS. FOR EASE OF REFERENCE, THE TWO ABBREVIATIONS LFLAND UFLAREUSED HEREINAFTER TO DENOTE THESE TWO SETS OF TERMS. IT SHOULD BE RECOGNIZED THAT PARTICULARAUTHORITIES HAVING JURISDICTION MAY PREFER THE USE OF ONE OF THE SETS OF TERMS AND NOT THEOTHER.

2.12 Full-scale gas concentration: the gas concentration that equals maximum scale indication.

2.13 Gas monitoring apparatus: an assembly of electrical and mechanical components (either a singleintegrated unit or a system comprised of two or more physically separate but interconnected componentparts) which senses the presence of combustible gas and responds by providing a meter indication, alarmfunction, and/or output functions.

NOTE: FOR CONVENIENCE, THE TERM APPARATUS IS USED AS AN ABBREVIATION FOR GAS MONITORINGAPPARATUS WITHIN THIS DOCUMENT.

2.14 Gas-sensing element (Transmitter/receiver): the primary element(s) in the gas monitoring system thatresponds to the presence of a combustible gas including any reference or compensating unit, whereapplicable.

2.15 Gaseous atmospheres2.15.1 Ambient air: normal atmosphere surrounding the apparatus.2.15.2 clean air: air which is free from gases or vapors (combustible, toxic or environmentally harmful

gases) to which the apparatus is sensitive or which influence the performance of the apparatus

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2.15.3 combustible atmosphere: a mixture with air, under normal atmospheric conditions, ofcombustible materials in the form of gas, vapor or mist, in which, after ignition, combustionspreads throughout the unconsumed mixtureNOTE 1: This definition specifically excludes dusts and fibers in suspension in air. Mists, though included in the definition

are not covered by this Standard

NOTE 2: Although a mixture which has a concentration above the upper flammable limit is not a combustible atmosphere,there is a risk of creating a combustible atmosphere by dilution.

2.15.4 combustible gas: a gas, which, when mixed with air in certain volumetric ratios, forms a com-bustible atmosphere

2.15.5 integral concentration: the mathematical integral of the gas concentration along the optical path.It is expressed in units of concentration multiplied by distance, e.g., LFL meter for combustiblegases or ppm meter for toxic gasesNOTE: 100%LFL 1 meter = 1 LFL meter;

10% LFL 10 meter = 1 LFL meter.

2.15.6 lower flammable limit (LFL): the volume ratio of combustible gas or vapor in air below whicha combustible gas atmosphere will not be formed

2.15.7 upper flammable limit (UFL): the volume ratio of combustible gas or vapor in air above whicha combustible gas atmosphere will not be formed

2.16 lower flammable limit meters (LFL m): a unit of measurement for the amount of gas present in thebeam. The LFL m represents the size of a gas cloud multiplied by the gas concentration within the cloud.See figure 1.1 of Appendix A.2.16.1 lower flammable limit/meters or Path Average (%LFL(Avg)): a unit of measurement for the

amount of gas present in the beam over the length of the beam. The %LFL(Avg) represents the sizeof a gas cloud multiplied by the gas concentration within the cloud divided by the beam lengthmultiplied by 100. See figure 1.2 of Appendix A.

2.17 Measurement range: the operable span region of the apparatus or a selected subdivision of that region.

2.18 Optical apparatus2.18.1 gas cell: a sealed enclosure with transparent ends which can be filled with test gases2.18.2 open path: an optical path which traverses the area (or part of the area) in which the atmosphere

is being monitored and through which gases in the atmosphere are free to move.2.18.3 optical radiation: the ultra-violet, visible or infra-red regions of the electromagnetic spectrum.2.18.4 receiver: an assembly in which the optical detecting element(s) are housed and which may contain

associated optical and electrical components.2.18.5 retroreflector: an individual or multiple arrangement of reflecting corners of cubes arrayed so that

light is reflected back parallel to its incident path.2.18.6 transceiver: an assembly in which the optical detecting element(s) and optical transmitting

element(s) are housed and which may contain associated optical and electrical components

2.19 Transmitter: an assembly in which the optical transmitting element(s) are housed and which may containassociated optical and electrical components

2.20 Response conversion data: information, supplied and explained in the apparatus instruction manual,enabling the apparatus user to determine the concentration of the gas to be monitored that will produce thesame response as a known concentration of another gas used for calibration.

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2.21 Signals and indications2.21.1 fault signal: an audible, visual, or other type of output which provides, directly or indirectly, a

warning or indication that the apparatus has been compromised2.21.2 beam blocked signal: an audible, visual or other type of output which provides, directly or

indirectly, a warning or indication that the optical path is obscured or that the signal detected is tooweak to enable the apparatus to function normally

2.21.3 inhibition signal: an audible, visual, or other type of output which provides, directly or indirectly,a warning or indication that normal operation has been suspended

2.21.4 indicating devices: means for displaying values or states in analog or digital form2.21.5 special state: all states of the apparatus other than those in which monitoring of gas concentration

take place, for example warm-up, calibration mode or fault condition

2.22 Span: the algebraic difference between the upper and lower values of a range.

2.23 Stand-alone control unit: control unit that is utilized with unspecified stand-alone detector head(s).

2.24 Stand-alone monitor: a combination transmitter and receiver either integral or remote that is (are) utilizedwith an unspecified control apparatus. Such apparatus is intended to be interfaced to a separate control unit,signal processing data acquisition, central monitoring, or other similar systems in which the apparatusprovides a conditioned electronic signal or output indication to systems of the aforementioned type thattypically process information from various locations and sources including, but not limited to, gas moni-toring apparatus.

2.25 Stationary apparatus: a gas monitoring apparatus intended for permanent installation in a fixed location.

2.26 Transportable apparatus: apparatus which is not intended to be portable, but which can be moved fromone place to another and used after alignment.

2.27 Zero: the lower calibration value, normally clean air.

3. GENERAL REQUIREMENTS

3.1 Review of Documentation

During the initial investigation and prior to physical testing, the manufacturers specifications and details shallbe reviewed to assess the ease and practicality of installation and use. The certification investigation shall definethe limits of the certification.

If any of the manufacturers published claims exceed any of the test condition extremes described in Section 4,the tests shall be conducted under the conditions for which the claims apply.

All claims not tested and verified by the certification agency as part of the certification investigation must beclearly identified as such in the products installation and operation manual. Alternatively, the manufacturer mayinclude a section or appendix in the manual which clearly itemizes the specifications, features, functions andrestrictions included in the certification.

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3.2 Markings

3.2.1 Marking on the product or, if not possible due to size, on its packaging or label accompanying the product,shall include the following information: Manufacturers name or trademark and address Specific model designation and serial number Apparatuss ratings (voltage, frequency, current or power, etc.) Apparatuss operating ambient temperature range

3.2.2 The model or type identification shall correspond to the manufacturers catalog designation and shalluniquely identify the product as Listed or labeled.

3.2.3 The Certification Mark shall be displayed visibly on the product and/or packaging as appropriate. Themanufacturer shall not use this mark on any other product unless such product is covered by separateagreement with the certification agency.

3.2.4 All markings shall be legible and durable.

3.2.5 The marking required in 3.2.6 shall appear in a clearly legible, visible, and permanent manner on each gasmonitoring apparatus in the following manner, as applicable:a) For stationary apparatus, the marking required in 3.2.6 shall appear in a location where it will be visibleafter installation and in direct sight during the routine periodic re-calibration and adjustment of set point(s).NOTE 1: For modular control units comprising one or more control modules in a common enclosure or mounting assembly, the

marking need not be repeated on each module, but may appear as a single marking on the common portion of theassembly.

NOTE 2: Where the design of a stationary control unit is such that there is insufficient space for this marking to appear on theportion of the unit that is visible after installation (e.g., compact designs for close panel mounting), the marking requiredby 3.2.6 is permitted to appear elsewhere on the control unit, provided that a second duplicate label (with an acceptableadhesive) bearing such marking is supplied with each such control unit (or assembly of control units), together with theinstructions that it is to be attached by the user in a conspicuous location after installation, as close as possible to thecontrol unit.

3.2.6 All open path gas monitoring apparatus shall be marked:CAUTION READ AND UNDERSTAND INSTRUCTION MANUAL BEFORE OPERATING ORSERVICING.The word CAUTION of the foregoing shall be in capital letters at least 3.0 mm high. The balance ofthe wording shall be in capital letters at least 2.5 mm high.

3.2.7 Where the design of special features of the apparatus requires additional markings or a change in markingrequirements, the additions or revisions are allowed, but the safety and instructional intent of this sectionmust be met.

3.3 Manufacturers Installation and Operation Manuals

3.3.1 Each gas monitoring apparatus shall be provided with an instruction manual, furnished by the manufac-turer. The instruction manual shall contain clear and precise instructions for safe and proper operation,installation and periodic servicing of the apparatus. The requirements of Sections 3.3.1 and 3.3.3 shall beincluded as applicable. Where the design or special nature of the apparatus requires additional instructionsthat are in contradiction of, or in addition to, the requirements of Sections 3.3.1 and 3.3.3, this consid-eration may take precedence over these requirements. Instructions shall be consistent with the markingsrequired in Section 3.2.

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3.3.2 The following requirements shall be incorporated in the manufacturers instruction and operation manuals:Each apparatus shall be provided with an instruction manual that includes the following information:3.3.2.1 complete instructions, drawings and diagrams for safe and proper operation, installation and

servicing of the apparatus;3.3.2.2 operating instructions and adjustment procedures;3.3.2.3 recommendations for initial checking and calibration of the apparatus on a routine basis, including

instructions for the use of the field calibration kit, if provided.3.3.2.4 details of operational limitations, including, where applicable, the following:

1) Gases for which the apparatus is suitable and the relative sensitivities of the instrument tothese gases

2) Information that describes the sensitivities to other gases to which the apparatus is responsive3) Temperature limits4) Humidity ranges5) Supply voltage limits6) Relevant characteristics and construction details of required interconnecting cables7) Battery data8) Pressure limits

10) Warm-up time11) Stabilization time

3.3.2.5 details of storage life and limitations for apparatus, replacement parts, and accessories, including,where applicable, the following:

1) Temperature2) Humidity3) Time4) Pressure

3.3.2.6 information on the adverse effects of poisons and interfering gases or substances and oxygen-enriched or deficient atmospheres on the proper performance (and, in the case of oxygen-enrichedatmospheres, on electrical safety) of the apparatus;

3.3.2.7 statements of the nature and significance of all alarms and fault signals, the duration of suchalarms and signals (if time-limited or non-latching) and any provisions that may be made forsilencing or resetting such alarms and signals, as applicable;

3.3.2.8 details of any method for determination of the possible sources of a malfunction and any correctiveprocedures (i.e., trouble-shooting procedures);

3.3.2.9 a statement that alarm devices, outputs, or contacts are of the non-latching types, where applicable.3.3.2.10 for battery-operated apparatus, installation, and maintenance instructions for the batteries;3.3.2.11 a recommended replacement parts list;3.3.2.12 where optional accessories (e.g., collecting cones, weather-protecting devices) are supplied, the

manufacturer shall list them and state their effects on the instrument characteristics (e.g., includ-ing response time and sensitivity) and provide means for identification of these (e.g., partnumbers included in manual);

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3.3.2.13 details of certification and marking and any special conditions of service;3.3.2.14 the storage life and recommended storage conditions for replacement parts and accessories,

where critical;3.3.2.15 where the special nature of the apparatus (such as non-linear responses) requires additional

instructions or special information that are alternative to, or in addition to, the requirements of3.3 and 3.4 a) to q), the instructions or information shall be provided. Consideration of knownconditions that may impair the reliability of the open path gas monitor.

3.3.2.16 Instructions of maintenance and calibration on a routine basis, following exposure of any of theconditions referred to in section 3.3.2.15 and following exposure to concentrations causingoperation of any alarm.

3.3.2.17 Wording equivalent to the following:FINAL AND LONG-TERM EFFECTIVENESS OF ANY OPEN PATH GAS MONITORDEPENDS HEAVILY UPON THE USER, WHO MUST BE RESPONSIBLE FOR ITSPROPER APPLICATION, INSTALLATION, USE, AND REGULAR MAINTENANCE.

3.3.2.18 Complete installation and initial start-up instructions. Including dimensional drawing showingmounting details.

3.3.2.19 A list of operating adjustments and instructions (e.g., alarm set point adjustment, zero and spanadjustments, etc.)

3.3.2.20 A list of apparatus specifications to include as a minimum: maximum and minimum storage andoperational limits including humidity and temperature of all parts of the apparatus. The speci-fications shall also include: accuracy, response times, voltage range (nominal voltage may bespecified but the range must also be included), operating amperage and start-up inrush current forall parts of the apparatus.

3.3.2.21 A list of operational limitations which include, as applicable, maximum length of lines, loopresistance, and minimum wire size for wiring between the control unit, transmitter, and receiverneeded for shielding of wiring, characteristics of nonlinear meters or indicators, warm-up time,air velocity limitations, battery charging, battery life and temperature limitations, sensor lifelimitation, pressure limits, sample-draw range of flow rates and lag times, sample-draw pressureand tubing size, etc.

3.3.2.22 If applicable, a statement to the user to be aware that extended exposure of a sensor to certainconcentrations of combustible gases in air may introduce stress to the sensor that could seriouslyaffect its performance and that calibration should be carried out and/or the sensor replaced afteran alarm due to indication of a high concentration.

3.3.2.23 Wording to provide for a clear indication of the nature and significance of all alarms and troublesignals, duration of any time-limited or self-restoring alarms or signals, provisions which may bemade for silencing or resetting alarms, alarm tolerances and set point limitations, and an indi-cation of any alarm devices, outputs or contacts that are of the non-latching type, as applicable.

3.3.2.24 The type of calibration gas or vapor mixture to be used. If the apparatus is designated to monitorgases other than the one for which it is calibrated, include response conversion data with specificinstructions as to its use.

3.3.2.25 A listing of consumable or replacement parts and recommendation of the storage type, environ-ment and installation instructions.

3.3.2.26 If more than one type of sensor is supplied by the manufacturer, include a list stating the specificgas family or chemically similar gases for each sensor.

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3.3.2.27 For an apparatus which provide measurement outputs (e.g., 4-20 mA signal), the instructionmanual shall provide graphs or other means to indicate the relationship between the input and theoutput.

3.3.2.28 Clarification that the apparatus will integrate the measurement over the full length of path to areading that represents the diameter of the cloud at 100%LFL concentration regardless of theactual concentration. This section shall provide multiple examples of gas clouds varying in sizeand concentration that will produce the same indication. Additionally, it shall recommend thatuser determine the size cloud they wish to prevent against and set the alarm points as a fractionof the determined cloud size not to exceed 60% of the determined cloud size.

3.3.3 For stand-alone monitors, specifications shall be supplied with the apparatus that describe the relationshipof the gas concentration detected by the apparatus, to the corresponding output signal or indication. Suchspecifications shall be detailed to the extent that the accuracy of the output or signal indication can beverified. As a minimum, the manufacturer shall provide data showing the relationship between the outputsignal or indication of the apparatus and gas concentrations corresponding to 0, 10, 25, 50, 75 and 100%of full-scale indication. Full-scale output shall be as specified by the manufacturer.

3.3.4 Communication optionsFor apparatus providing communications options that are not included in the Certification examination butwhich comply with requirements of Section 4.3 (NOTE 2), the following shall appear in the instructionmanual:As part of this Certification, it was verified that optional communication functions of this gas monitoringapparatus while operating at the maximum transaction rate do not adversely affect the gas monitoringoperation and functions of the apparatus. This Certification, however, does not include or imply Certifi-cation of the communications protocol or functions provided by the software of this apparatus or of thecommunications apparatus or software connected to this apparatus.

3.4 Construction and Functions

3.4.1 General requirementsAny portion of a gas monitoring apparatus shall be listed or labeled for the intended area of installationwith respect to unclassified or hazardous (classified) locations. Where apparatus are used within hazardous(classified) locations shall be suitable for use in Class I, Division 1 or 2 or Class I, Zone 0, 1 or 2 hazardous(classified) locations.Gas monitoring apparatus and their components specifically intended for use in the presence of corrosivevapors or gases, or that may produce corrosive by-products as a result of catalytic oxidation or otherchemical process shall be constructed of materials resistant to or suitably protected against corrosion.

3.4.2 Meters, indicators and outputs3.4.2.1 Apparatus having an integral meter or indicator to indicate gas concentrations shall employ a

meter having sufficient resolution to permit measurement with the precision required for the testsof Section 4.

3.4.2.2 Operational characteristics of nonlinear meters or indicators, when used, shall be stated in theinstruction manual.

3.4.2.3 A means shall be provided to alert the user that a gas concentration in excess of the measuringrange of the apparatus has been detected.

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3.4.2.4 If individual colored indicating lights are provided, they shall be colored as follows:a) alarms indicating the presence of a gas concentration above an alarm set point shall be colored

RED;

b) equipment fault indicators shall be colored YELLOW;c) power supply indicators shall be colored GREEN.In addition to the color requirements, the indicator lights shall be labeled to show their functions.

3.4.3 Alarm or output function3.4.3.1 Alarm devices, output contacts, or signal outputs (if provided and intended to indicate a potentially

flammable gas concentration) shall be of a latching-type requiring a deliberate manual action toreset. If two or more set or alarm positions are provided, the lower may be non-latching.

NOTE: The latching requirement may be omitted or a defeating option permitted only when a clear and prominent statement in theinstruction manual specifies that the apparatus shall be connected to an auxiliary system which accomplishes the samepurposes as latching.

3.4.4 Trouble signals3.4.4.1 A stationary or transportable gas monitoring apparatus shall provide for a signal transfer or contact

transfer to produce a trouble signal if any of the following conditions occur:a) apparatus power failure;b) loss of continuity in any one or more conductors to any remote detector head;c) loss of continuity of any gas-sensing element;d) down scale indication (below zero) equivalent to prior to 10% of full scale; ore) beam blockage.Such signal or contact transfer shall be differentiated from any other alarm or shutdown signal orcontact transfer.

3.4.4.2 If the manufacturer provides a mechanism that will disable alarm outputs for maintenance orcalibration purposes, that mechanism shall either trip the fault signal and produce a visual indi-cation or provide a similar independent set of signals.

3.4.5 Controls and adjustments3.4.5.1 Calibration and alarm(s) setting shall be designed to discourage unauthorized or inadvertent

interference with the setting(s). Examples of acceptable methods include mechanical devices (suchas a cover requiring the use of a tool) and passwords (input by authorized users).

3.4.5.2 Fixed explosion-protected apparatus housed in explosion-protected enclosures shall be designedso that, if any facilities for adjustment are necessary for routine recalibration and for resetting orlike functions, they shall be externally accessible. The means for making adjustments shall notdegrade the explosion protection of the apparatus.

3.4.5.3 Measurement indications and output signals (e.g., current loop, voltage, etc.) of stand-alonemonitors shall have the ability to be calibrated for zero and span, with or without the presence ofa control unit (use of simulated control unit input is satisfactory).

3.4.5.4 Analog measurement input signals (e.g., current loop, voltage, etc.) and indications of stand-alonecontrol units must have the ability to be calibrated for zero and span, with or without the presenceof a detector head (use of simulated detector head output is satisfactory).

3.4.5.5 Auxiliary measurement output signals (e.g., 4-20 mA, voltage, etc.) provided with gas monitorsor control units must have the ability to be individually calibrated for zero and span.

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3.4.6 Enclosures3.4.6.1 Apparatus enclosures, including associated accessories, marked with an environmental rating as

specified by the manufacturer shall be tested for such locations.3.4.6.2 All parts of the apparatus subjected to the combustible gas atmosphere to be monitored shall be

suitable for that location.

3.5 Test Equipment Calibration

All examinations and tests performed in evaluation to this standard shall use calibrated measuring apparatustraceable and certified to acceptable national standards.

4. PERFORMANCE REQUIREMENTS

4.1 General

a) The tests required in this section are in addition to the requirements of applicable standards referred to inSection 3.4.1

NOTE: Examination and tests required in applicable standards in Section 3.4.1 shall be satisfactorily completed prior to the start of testsrequired in this section and any modifications or changes resulting from those requirements shall be incorporated in the apparatusunder test.

b) The apparatus tested shall be fully representative of apparatus intended for commercial production.

c) Unwarranted or false alarms shall be considered failure of the tests described below.

d) All output indications and signals, not directly scaled in either LFL m or %LFL(Avg), shall be converted tothe applicable concentration readings. The converted value(s) shall be used for determination of all deviationsfrom standard requirements. For example, the conversion of a 4-20mA output to %LFL(Avg) concentrationshall be performed using the following formula:

Im 4)Measurement (%LEL / m) = Fullscale16

Where: Im is the measured 4-20 mA loop current in mAFull-scale is the apparatuss maximum measurement range value

e) Tests shall be conducted with all equipment installed as intended for use.

f) For multiple gas sensing apparatus, all unwarranted (false) alarms which require re-setting, re-adjusting, etc.,to continue open path gas monitoring tests shall be considered a failure.

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4.2 Samples and Sequence

Previously untested apparatus including all optional or accessory parts to be used on the final Listed or labeledapparatus shall be subjected to all tests applicable to that apparatus type as described in the following sections.The apparatus tested shall be fully representative of apparatus intended for commercial production. All apparatusshall be subjected to the test in section 4.5.

4.3 Preparation of Apparatus

The apparatus selected for testing shall be prepared as if for actual service, including all necessary intercon-nections and initial adjustments, in accordance with the manufacturers instruction manual.NOTE 1: For apparatus having remote receiver, all tests shall be performed with resistors (with temperature coefficients similar to those

of the recommended interconnecting conductors) connected in the detector circuit to simulate the maximum line resistancespecified by the apparatus manufacturer, except where minimum line resistance offers a more stringent test.

NOTE 2: For apparatus having serial or parallel communications options, tests in Sections 4.7, 4.8, 4.9, 4.13, 4.16 and 4.23 shall beperformed with all communications ports connected to apparatus which initiates the maximum transaction rate and activity levelspecified by the apparatus manufacturer. Special apparatus may be used to simulate the communications activity and must beprovided by the manufacturer. (See Section 3.3.4)

NOTE 3: For apparatus that are part of a system evaluated for Certification, tests in Sections 4.7, 4.8, 4.9, 4.13, 4.16 and 4.23 shall beperformed with the maximum system communications transaction rate and activity level which would result from the largest andmost complex system configuration. Special apparatus may be used to simulate the system activity and must be provided by themanufacturer.

4.4 Conditions for Test and Test Area

4.4.1 Use of gas cellsThe test facility shall be designed such that the test gas in individual cells can be changed and that whenusing the equipment the cells can be exchanged sufficiently quickly in order that transient obscurationduring the exchange by the walls or window retaining structure shall not create a beam blockedcondition. The transverse dimension of the cells shall be large enough not to cause partial blockage of thebeam.

NOTE 1: The test described in 4.6 and 4.12 may require cells of large dimensions or the use of an alternate gas simulation filter.

Cells shall be located as close as possible to the receiving aperture of the apparatus having regard tominimizing unwanted effects on the apparatus of reflections from the cell on the receiver and the need notto cause partial blockage of the beam.The characteristics (e.g., material, thickness and flatness) and inclination of the windows of the cells shallbe chosen to minimize the effects of reflection, distortion and attenuation of the beam over the effectivebandwidth of the measuring radiation. Errors in measurement arising from variations of attenuation withwavelength in the window material shall be as specified in subsequent parts.The axial length of the cells may be chosen in relation to the concentration of the gas filling the cells toprovide standard values of integral gas concentration for use in calibration.Cells may be filled with test gases including, for example, clean air (for zero setting) and the gas to bemeasured. Cells used for zero setting shall have minimal effect on apparatus calibration. Heating may beapplied to cells to ensure that vapor, condensable at room temperature, can be maintained in the gaseousstate.

NOTE 2: To avoid using large volumes of potentially combustible gas and air mixtures, cells of appropriate length filled with test gas ofsubstantially less than 100%LFL may be used for small path integral concentrations, (e.g., 0.5 LFL 1 meter), and either100%V/V combustible gas or mixtures of combustible and inert gas may be used for larger integral concentrations.

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For the water vapor interference test of 4.19, the cell shall be 1m in length and be capable of containingwater vapor at atmospheric pressure. To prevent condensation, the cell walls and windows shall be heatedto a temperature in excess of 100C. Gas cells used for tests with combustible gases shall be constructedsuch that errors in measurement arising from variations of attenuation with wavelength in the windows ofthe cells shall be less than 2% of measuring range or 5% of the measured value, whichever is greater.

4.4.2 Mask for beam attenuationThe attenuation produced by fog, precipitation and dust in the optical path, and material deposited onoptical surfaces shall be simulated by a mask (for example an opaque grid in the form of a mesh with mattblack surfaces) inserted into the beam path. The mask, used for the tests described in Error! Referencesource not found. and 4.21, shall have proportions chosen to transmit (5 1) % of the incident beam at50% of the maximum path length of the open path apparatus.

4.4.3 Shutter for blockage testsTo test the response of the apparatus to controlled blocking of the beam as in 4.20.1, an opaque shutter,sufficiently large to intercept all of the measuring radiation, with matt black absorbing surfaces and astraight leading edge shall be capable of being driven across the measuring radiation at a uniform speedof approximately 10 mm/s until the beam is completely blocked and then reversed at the same speed untilthe shutter is completely withdrawn. For the test described in 4.20.2 the facility for driving at 10 mm/s isnot required.

4.4.4 Plane mirrorCalibrations and tests may be carried out using a front metallized plane mirror to fold the beam path, tominimize the space required. The characteristics (e.g., material and flatness) of the mirror shall be chosento minimize distortion and attenuation of the beam over the effective bandwidth of the measuring radia-tion. The change in signal strength caused by the introduction of the mirror shall not exceed 5%.

4.4.5 Gas simulation filterFor the tests described in 4.6 and 4.12 it is permissible to use a gas simulation filter consisting of a thinsheet of appropriate material, for example polypropylene in the case of combustible gases, to produce anattenuation of the beam equivalent to 30% to 70% of the full scale gas concentration. The dimensions ofthe filter shall be greater than the maximum transverse dimensions of the optical beam and such that allof the reflected solar radiation in the test described in 4.12 is incident on the suns disc.Test filters shall not be used for measurement value. The test filter shall be used as a repeatable value only.At the start of the test the test filter shall be inserted into the beam path. The initial indicated reading shallbe recorded. Subsequent readings shall be referenced to the initial indicating reading.

4.4.6 Normal conditions for test4.4.6.1 General

The test conditions specified in 4.4.6.2 to 4.4.11 shall be used for all tests unless otherwise stated.4.4.6.2 Operating distance for laboratory tests

The distance between source and receiver or between transceiver and reflector for all tests shallbe in the range of 5 to 20m or the maximum distance if shorter. Operating distances greater than20 m shall be agreed upon between the manufacturer and the certification agency.

4.4.6.3 Test gasesThe gases or gas mixtures to be used for initial and all subsequent tests shall be those for whichcompliance with this standard is claimed.

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4.4.7 Test gas integral concentrations4.4.7.1 Mid-range integral concentration

The standard test gas shall be the type of gas for which compliance of the apparatus with thisstandard is claimed and its concentration in the chosen cell shall be such as to provide an integralconcentration equivalent to a value in the middle of the apparatuses range of measurement of theapparatus and known to an uncertainty of 5%.

4.4.7.2 Other path integral concentrationsOther values of standard path integral concentration as required for calibration (4.7) and alarmreliability (4.11.2) are specific to the apparatus measuring range and alarm settings of individualapparatus. For each gas the integral concentration shall be known to within 5%.

NOTE: The gas mixture may be prepared by any suitable method, e.g., in accordance with the methods outlined in ISO 6142, ISO6144, ISO 6145 and ISO 6147.

4.4.8 VoltageExcept as otherwise indicated herein, all tests shall be performed at the nominal system voltage andfrequency marked on the equipment, or, if applicable, with fresh or fully charged batteries.

4.4.9 Ambient temperatureExcept as otherwise indicated herein, tests may be performed at conveniently available room ambienttemperatures in the range of 18C to 30C.

4.4.10 HumidityExcept as otherwise indicated herein, tests may be performed in ambient air having a relative humidityof any convenient value in the range of 30 to 70%.

4.4.11 Pressure

During individual tests, other than the long term drift test, the pressure of the ambient air and test gas shallbe the same and at a value 1 kPa within the range 86 kPa to 108 kPa.

4.4.12 Removal of partsFor purposes of the tests in Sections 4.5 through 4.23, where reference is made to exposing the sensinghead to specified gas mixtures or to other specified conditions, in the case of remote detector heads, theentire head, including all normally attached diffusion devices or protective mechanical parts, shall be soexposed.

4.4.13 Re-calibration or adjustmentThe apparatus under test may be adjusted or re-calibrated prior to the start of each test described inSections 4.6 and 4.8 through 4.23. However, no further adjustments or re-calibration shall be carried outfor the duration of that test except where specifically permitted by the particular test procedure.

4.4.14 Stabilization timeUnless otherwise stated within the test condition, each time the apparatus is subjected to a different testcondition, the apparatus shall be allowed to stabilize under these new conditions (see note below) beforemeasurements are taken for comparison purposes.NOTE: An apparatus shall be considered to be stabilized when three successive observations of the indication taken at 5-min

intervals indicate no significant change.

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4.4.15 Apparatus having alarms onlyApparatus having alarms only do not have any meter or other outputindication that can be compared before and after the tests described in Section 4. For purpose of the test,the alarm set point shall be set at 20% full scale and a tolerance of 5% full scale applied for all tests.

4.4.16 Stand-alone gas detection apparatus for use with separate control units4.4.16.1 General

Section 4.4.16 includes apparatus that provide a conditioned electronic signal or outputindication intended to be used with separate signal processing, data acquisition, central moni-toring or other similar systems which typically process information from various locations andsources including, but not limited to, gas detection apparatus.

4.4.16.2 Transfer function specificationA specification shall be supplied with the apparatus thatdescribes the relationship of the gas concentration, detected by the apparatus, to the corre-sponding output signal or indication (transfer function). Such specification shall be detailed tothe extent that the accuracy of this transfer function can be verified. As a minimum, themanufacturer shall provide data showing the relationship between the output signal and the gasconcentrations corresponding to 0, 10%, 25%, 50%, 75% and 100% of full scale outputindication. Full scale output shall also be as specified by the manufacturer.

4.4.16.3 Provision for transfer function verificationWhere necessary, equipment shall be provided by themanufacturer to interpret the output signal or indication which will enable the accuracy of thetransfer function to be verified.

4.4.17 Separate control units for use with stand-alone gas detection apparatus4.4.17.1 General

Section 4.4.17 includes those apparatus to be used with stand-alone gas monitor (as defined inSection 2.23) to complete a performance evaluated open path combustible gas monitoringsystem.

4.4.17.2 Tests

The control units shall be tested to the requirements of Sections 4.5, 4.6, 4.7, 4.8, 4.9, 4.12, 4.13,4.14, 4.15, 4.16, 4.17, 4.18, 4.20 , and 4.23 using the parameters of the transfer functionpertinent to the specific type of gas detector.

4.4.18 Selectable gas/range apparatus4.4.18.1 For apparatus having more than one selectable range or scale for the same gas, the tests in

Sections 4.6 and 4.8 through 4.23 shall be performed with the apparatus operating at both theleast and most sensitive ranges, except that if the most sensitive range has a full scale equal toor less than 25% of the full scale, the performance shall be that specified by the manufacturerin the instruction manual. If the manufacturer does not state the performance characteristics ofthe most sensitive scale where it is 25% of full scale or less, the performance shall be the sameas for the least sensitive range.

4.4.18.2 For apparatus having selectable ranges employing different detecting means, all of these testsshall be performed on each range.

4.4.18.3 For apparatus having specific ranges or scales for different gases:a) After only one vibration test performed per Section 4.6, the tests in Section 4.6 shall be

repeated at each selectable range for each gas.b) The tests in Sections 4.9 through 4.23 shall be repeated at each selectable range for each gas.

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4.5 Un-Powered Preconditioning Storage

Prior to tests in Sections 4.6 through 4.23, all parts of the open path monitoring apparatus shall be exposedsequentially to the following conditions:

a) Temperature of -35C for 24 h

b) Ambient temperature and humidity for at least 24 h

c) Temperature of +55C for 24 h

d) Ambient temperature and humidity for at least 24 h

NOTE: The temperature extremes in section 4.5 are considered minimum requirements. If the open path monitoring apparatus is intendedto be stored or operated in temperature ranges beyond these limits the greater limit of the manufacturers specifications shall beused.

4.6 Vibration

The transmitter and the receiver shall be mounted together or separately on the vibration test machine andvibrated successively in each of three mutually perpendicular directions, respectively parallel to the edges of theapparatus. The apparatus shall be mounted on the vibration table in the same manner and position as intendedfor service using any resilient mounts, carrier, or holding devices that are provided as a standard part of theapparatus. Adjustable alarm apparatus shall be set to the lowest alarm level or 10% of the measuring range,whichever is greater.

The instrument shall be vibrated over a frequency range of 10 Hz to 30 Hz at a total excursion of 1mm and 31Hz to 150 Hz at a 2 g acceleration peak for a period of 1 hour in each of three mutually perpendicular directions.The rate of change of frequency shall not exceed 10 Hz/min This test procedure shall apply to the remote detectorhead and the control unit.

The apparatus shall not give any false alarms; there shall be no loose components or damage to the enclosurethat could cause a hazard, and, when tested with clean air and the initial calibration mixture, the reading shallbe accurate within 7.5% of full-scale gas concentration after this test. In lieu of the test criteria above, apparatusincorporating alarms only shall be actuated by a 24 to 26% the full scale but not be actuated by a 14 to 16% thefull scale after this test.

NOTE: Trouble or fault signals due to miss alignment during the testing shall be permitted

4.7 Calibration

The apparatus shall be calibrated for testing in accordance with this standard using manufacturers calibrationfixture and specified calibration procedures. The calibration gas shall be a nominal 50% of the apparatussfull-scale gas concentration. The combustible gas to be used shall be as follows:

Methane for apparatus intended for sensing methane specifically, or intended for general-purpose combustiblegas detection (including detection of methane).

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Propane for apparatus intended for general-purpose combustible gas detection that excludes methane.

The actual specific gas or a representative gas for apparatus intended for sensing a specific combustible gas ora specific family of chemically similar combustible gases.

NOTE 1: When apparatus can be used for detecting more than one combustible gas by changing only the gas-sensing element, then onlythose tests, with the exception of 4.13, 4.14, and 4.16, need to be repeated for the second and subsequent gases. Methane shallbe tested first if a methane sensing element is supplied by the manufacturer.

NOTE 2: Unless otherwise indicated herein, the manufacturers calibration device is to be used to supply the gas mixture to the gas-sensingelement for the tests described in the paragraphs that follow. However, the apparatuss response utilizing this method and theapparatuss intended method of gas monitoring, if different, shall first be established.

NOTE 3: Gas mixtures having the same concentrations as those used for tests in Section 4.7 are used for various other tests described inthe paragraphs that follow. For ease of reference, such gas mixtures will hereafter be referred to simply as the initial calibrationgas mixture.

4.8 Accuracy

All test gas concentrations shall be known to a tolerance of 2% of %LFL value. The apparatus shall be exposedto four volume ratios evenly distributed over the measuring range, starting with the lowest and finishing with thehighest of the selected volume ratios. In each case, the concentration indicated by the meter or output signal shallnot vary from the known test gas concentration by more than 5% of full-scale gas concentration or 10% ofapplied gas concentration, whichever is greater. Alarm functions shall be verified to actuate when respectiveset-point values are crossed.

4.8.1 For apparatus having alarms only, testing shall verify that each alarm 1) actuates on exposure to gas-airmixtures whose concentrations are at the upper tolerance limit for alarm actuation; and 2) does not actuateon exposure to mixtures whose concentrations are below the lower tolerance limit. (See Section 4.7.)

4.9 Trouble Signals

The apparatus shall be placed into the following conditions to verify proper trouble signaling:

a) apparatus power failure;

b) loss of continuity in any one or more conductors to any remote detector head;

c) loss of continuity of any gas-sensing element;

d) down scale indication (below zero) prior to 10% of full scale;

e) beam blockage.

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4.10 Temperature

The apparatus shall be exposed to specified temperature extremes by using a temperature chamber capable ofmaintaining the specified temperature within 2C. When the apparatus (or the portion under test) has reachedthe temperature specified in this section, the apparatus shall be exposed to the standard test gas. If the apparatusincludes temperature compensation, the standard test gas shall be exposed to the same temperature as theapparatus.

The tests shall be performed at the more onerous of the manufacturers rated temperature conditions or thefollowing temperature conditions shall be applied to the apparatus or items of the apparatus:

i) The energized transmitter or transceiver shall be placed in a chamber maintained at (55 2) C ambient fora minimum of three hours or until stabilized within 2C for a minimum of 1 hour while the receiver orreflector is maintained at room temperature. At the conclusion of the test, a gas cell at (23 2) C ambientshall be applied and readings recorded.

ii) The energized transmitter or transceiver shall be placed in a chamber maintained at (-25 2) C ambientfor a minimum of three hours or until stabilized within 2C for a minimum of 1 hour while the receiveror reflector is maintained at room temperature. At the conclusion of the test, a gas cell at (23 2) Cambient shall be applied and readings recorded.

iii) The energized receiver, if applicable, shall be placed in a chamber maintained at (55 2) C ambient fora minimum of three hours or until stabilized within 2C for a minimum of 1 hour while the transmitteror transceiver is maintained at room temperature. At the conclusion of the test, a gas cell at (23 2) Cambient shall be applied and readings recorded.

iv) The energized receiver, if applicable, shall be placed in a chamber maintained at (-25 2) C ambient fora minimum of three hours or until stabilized within 2C for a minimum of 1 hour while the transmitteror transceiver is maintained at room temperature. At the conclusion of the test, a gas cell at (23 2) Cambient shall be applied and readings recorded.

v) If the indicator or control unit is normally mounted separately from the transmitter and receiver, forexample in a control room, the temperature of the indicator or control unit shall be varied over the range5 C to 55 C while the transmitter and receiver are maintained at room temperature.

There shall be no loss of functionality and the variation of the measured value from the claimed temperaturerange during testing shall not exceed 7.5% of full-scale gas concentration or 15% of applied gas concen-tration measurement at room ambient, whichever is greater.

ALTERNATE TEST:

The following alternate test may be performed in replacement of the previous temperature test:

The tests shall be performed at the more onerous of the manufacturers rated temperature conditions or thefollowing temperature conditions shall be applied to the apparatus or items of the apparatus:

i) The energized transmitter or transceiver and the receiver or reflector shall be placed in a chamber main-tained at (55 2)C ambient for a minimum of three hours or until stabilized within 2C for a minimumof 1 hour. At the conclusion of the test, a gas cell at (55 2)C ambient shall be applied and readingsrecorded.

ii) The energized transmitter or transceiver and the receiver or reflector shall be placed in a chamber main-tained at (-25 2)C ambient for a minimum of three hours or until stabilized within 2C for a minimumof 1 hour . At the conclusion of the test, a gas cell at (-25 2)C ambient shall be applied and readingsrecorded.

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iii) If the indicator or control unit is normally mounted separately from the transmitter and receiver, forexample in a control room, the temperature of the indicator or control unit shall be varied over the range5 C to 55 C while the transmitter and receiver are maintained at (23 2)C.

iv) The energized transmitter or transceiver shall be placed in a chamber maintained at (20 2)C above roomtemperature for a minimum of three hours or until stabilized within 2C for a minimum of 1 hour whilethe receiver or reflector is maintained at room temperature. At the conclusion of the test, a gas cell at roomtemperature shall be applied and readings recorded.

v) The energized transmitter or transceiver shall be placed in a chamber maintained at (20 2)C below roomtemperature for a minimum of three hours or until stabilized within 2C for a minimum of 1 hour whilethe receiver or reflector is maintained at room temperature. At the conclusion of the test, a gas cell at roomtemperature shall be applied and readings recorded.

vi) If the indicator or control unit is normally mounted separately from the transmitter and receiver, forexample in a control room, the temperature of the indicator or control unit shall be varied over the range5C to 55C while the transmitter and receiver are maintained at room temperature.

There shall be no loss of functionality and the variation of the measured value from the claimed temperaturerange during testing shall not exceed 7.5% of full-scale gas concentration or 15% of applied gas concen-tration measurement at room ambient, whichever is greater.

4.11 Time of Response

4.11.1 Measuring apparatusUsing test equipment designed and operated in accordance with 4.4, a cell containing mid-range integralconcentration, as 4.4.7.1, of standard test gas, as 4.4.6 shall be rapidly exposed to the optical path.The time (t90) taken to reach 90% of the final reading of the standard test gas path integral concentrationshall be recorded.A measured value of 90% of the final value shall be achieved in a time not exceeding 10 s.The sequence shall then be repeated except that the cell containing test gas shall be rapidly exchangedwith cell of the same dimensions containing clean air. The recovery time for the signal to decay to 10%of the test gas reading shall be recorded.A measured value shall indicate 10% of the previous final value in a time not exceeding 10 s.

4.11.2 Alarm only apparatusUsing test equipment designed and operated in accordance with 4.4, a cell containing test gas withintegral concentration of (120 10)% of the value of the alarm set point concentration shall be rapidlyexposed to the optical path. The time interval from the step change to the initiation of the alarm shall berecorded.The procedure shall be repeated for other fixed alarm settings.For apparatus with adjustable alarms, the set points shall be adjusted to operate in the mid-band,approximately 40% to 60% of the span, of the range of settings.Following the positive step-change in integral concentration, the time taken to alarm shall not exceed10 s.

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4.12 Solar Radiation

Radiation from the sun shall be used for the test when the sun is at an inclination greater than 30 above thehorizon and the atmospheric condition must be a clear day with well defined shadows. The radiation shall bereflected from a plane front surface mirror towards the inlet aperture of the apparatus. An iris shall be insertedinto the suns radiation to ensure that only radiation from within the suns disc is reflected towards the inletaperture. The radiation intensity measured in front of the receiver inlet aperture shall be a minimum of750 W/m2, e.g., by the use of an appropriate filter or mask.

The intensity of radiation from the transmitter measured at the entrance of the receiver aperture shall beattenuated to the value experienced when operating over maximum path length.

A mid-range test cell or gas simulation filter as described in 4.4.5 shall be inserted into the beam close to thetransceiver or receiver and shall be of sufficient size to ensure that there is no obstruction of the reflectedradiation beam.

The mirror shall be orientated so that the inclination of the reflected solar radiation to the optical axis of theapparatus is fixed successively at +10, +3, -3 and -10 in two mutually perpendicular planes, the angulartolerance in each case being 1.

NOTE: Where it is possible to rotate a receiver or transceiver about its optical axis, an alternative arrangement is for the mirror to belocated successively at only two positions providing radiation incident at 10 1 and 3 1 to the optical axis and for the receiveror transceiver to be rotated about the optical axis of the apparatus through 01, 901, 1801 and 2701 in each of thecases.

At each inclination the apparatus shall be allowed to stabilize before measurements of the mid-range concen-tration are recorded.

Throughout the test the apparatus shall continue to operate and shall not generate inhibition fault or alarmsignals. The measured signal after stabilization at each of the angles of inclination shall not exceed 7.5% ofthe measuring range or 15% of the measured value, whichever is greater.

4.13 Power Supply Variations

4.13.1 GeneralThe apparatus shall be set up under normal conditions. It shall then be subjected to the tests specifiedin 4.13.2 to 4.13.4.For each of the conditions specified in 4.13.4, 4.13.3 and 4.13.4 the indication shall be checked at onepoint by inserting a test cell containing integral concentration of gas chosen to give a response near themiddle of the measurement range.

4.13.2 A.C. powered apparatusThe apparatus shall be checked when operated successively at 110% and 85% of the nominal supplyvoltage at the nominal supply frequency.The apparatus shall not generate any false alarms and the measured values of the integral concentrationfor each gas shall not differ from the nominal values by more than 5% of full-scale gas concentrationor 10% of the measured value, whichever is greater.

4.13.3 External D.C. powered apparatusThe apparatus shall be checked when operated successively at 115% and 80% of the nominal supplyvoltage.

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The apparatus shall not generate any false alarms and the measured values of the integral concentrationfor each gas shall not differ from the nominal values by more than 5% of full-scale gas concentrationor 10% of the measured value, whichever is greater.

4.13.4 Apparatus with other power supplies including batteriesThe apparatus shall be checked at the upper and lower limits of the supply voltage specified by themanufacturer.The apparatus shall not generate any false alarms and the measured values of the integral concentrationfor each gas shall not differ from the nominal values by more than 5% of full-scale gas concentrationor 10% of the measured value, whichever is greater. In the case of battery powered apparatus, theselimits shall apply when the apparatus is subject to a change from the maximum terminal voltage of anew or fully charged battery to the minimum recommended operating voltage of that battery asdetermined by the built-in battery condition indicator.

4.14 Power Supply Interruptions and Transients

4.14.1 GeneralAdjustable alarm apparatus shall be set so that the lowest alarm level is 10% of the calibrated measuringrange.

The apparatus shall be set up under normal conditions, in accordance with 4.3, and shall then besubjected to the tests specified in 4.14.2 to 4.14.3 in clean air only. The apparatus indication and alarmsshall be monitored during the tests. During the testing the apparatus shall not generate spurious fault oralarm signals. On completion of the tests, the indicated reading shall return to the value at the beginningwithin 2% of the initial measured value. The apparatus shall operate throughout the testing in accor-dance with the following requirements:a) Indicated readings to return to within 2% of initial measured value.b) No generation of alarm signals.c) No generation of spurious fault signals.

4.14.2 Short interruption of power supplyThe power supply shall be interrupted for 10 ms, repeated ten times at random time intervals having amean value of 10 s.

4.14.3 Step changes of voltageFor mains and d.c. powered apparatus the supply voltage shall be increased by 10%, maintained at thisvalue until stabilized, and then reduced to 15% below nominal voltage. Each step change shall takeplace within 10 ms.

4.15 Recovery from Power Supply Interruption

The apparatus shall be calibrated as in 2.3 and then operated with a gas cell in the beam containing an integralconcentration of 25% of the measuring range of the test gas. The power shall be switched off for 30 min andthe gas cell replaced by an equivalent optical cell containing an integral concentration of 50% of the measuringrange. The power shall then be restored and after stabilization the measured integral concentration shall benoted.

The measured integral concentration after restoration of the power shall be within 5% of the nominal valueof integral concentration contained in the test cell. Alternatively, the apparatus must indicate a latched inhibitcondition.

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4.16 Electromagnetic Interference (EMI)

Following satisfactory completion of all the applicable tests of the preceding clauses, the stationary or portableapparatus (including sensor, electronics, and interconnecting wiring) shall be subjected 1) while in an energized(operating) mode and 2) while in the position of normal calibration, to electromagnetic energy in the frequencyranges of 150 to 170 MHZ and 450 to 470 MHZ, using frequency-modulated portable radio transmitters (5 Winput to the final amplifier) at a distance of 1 m away from the apparatus (i.e., its sensor, electronics, andinterconnecting wiring). Tests shall be conducted for both items 1) and 2) above, using a randomly selectedfrequency within each of the two frequency ranges. These tests shall not cause the apparatus to produce outputchanges shall not exceed 7.5% of the measuring range or 15% of the measured value or result in an incorrectapparatus function. Tests should be conducted following the manufacturers suggestions concerning wiring,shielding, and installation techniques as they pertain to electromagnetic interference.

4.17 Partial Obscuration

The apparatus shall be calibrated as in 2.3. Introduce an obscuration mask, such that 50% of receiver apertureis obscured, and repeat in each of four orthogonal orientations. At each orthogonal orientation introduce a zeroand span gas concentration. In each orientation either a fault indication shall be given or the concentrationindicated by the meter or output signal shall not vary from the known test gas concentration by more than7.5% of full-scale gas concentration or 15% of applied gas concentration, whichever is greater.

4.18 Simulated Fog/Mist (Intended for Outdoor Use)

For an apparatus intended for outdoor use, introduce zero and span gas and record readings. Gradually increaseattenuation of the fog tunnel, as described in Annex A. When signal received by receiver has reduced by at least90% of original, introduce zero and span gas and record readings. The concentration indicated by the meter oroutput signal shall not vary from the known test gas concentration by more than 7.5% of full-scale gasconcentration or 15% of the initial measured value, whichever is greater.

Exception: Apparatus intended for indoor use only are not required to be subjected to this test.

4.19 Water Vapor Interference

Cells as described in 4.4.1, filled to atmospheric pressure with dry clean air and with water vapor concentration,shall be introduced successively into the path of the optical beam.

The water source shall be heated so that the temperature within the test cell shall be at least 95C prior toapplication of the test cell.

For apparatus incorporating alarms only, the alarm shall not be actuated by a test gas of 14 to 16% of full-scaleconcentration and be actuated by a test gas of 24 to 26% of full-scale concentration while exposed to bothhumidity extremes.

The measured values of the integral concentration for each gas shall not differ from the nominal values by morethan 7.5% of full-scale gas concentration or 15% of the initial measured value, whichever is greater.

NOTE: Care should be taken to prevent moisture from collecting on the windows of the cell.

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4.20 Beam Blockage Fault

4.20.1 Spurious alarmsAdjustable alarm apparatus shall be set so that the lowest alarm level is 10% of the calibrated measuringrange.

With the apparatus operating in air, the opaque shutter as described in 4.4.3 shall be driven across themeasuring radiation at a uniform speed of approximately 10 mm/s until the beam is completely blockedand then completely withdrawn at the same speed.The shutter shall be driven successively in each of four directions at 90 intervals in a planeperpendicular to the axis of the measuring radiation and at the following positions:i) for apparatus comprising a separate transmitter and receiver, the positions shall be close ( e.g., less

than 100 mm) to the transmitter and receiver;ii) for apparatus comprising a transceiver and reflector the positions shall be close ( e.g., less than

100 mm) to the transceiver and reflector.The apparatus shall continue to operate without generating spurious alarm signals until a beam blockedor inhibition signal is produced. On withdrawal of the shutter from the position of beam blocked orinhibition to complete removal, the apparatus shall again operate without generating spurious alarmsignals.

4.20.2 RecoveryWith the apparatus operating in ambient air, the opaque shutter shall be rapidly inserted into the beamin any one direction until an inhibition signal due to beam blockage is produced. While the beamblocked condition is indicated the mid-range standard gas cell shall be introduced into the beam positionand the shutter shall then be rapidly removed.The indication or output attained within 20 s of the removal of the shutter shall not differ from the valueof integral concentration in the test cell by more than 10 %.

4.21 Long Range Operation

The equipment shall be assembled for operation over the maximum operating distance, and adjusted intooperational state, in accordance with the manufacturers instructions, with ambient air in the optical path. Theapparatus shall be allowed to stabilize.

The mask defined in 4.4.2 shall then be inserted into the beam in the manner described therein. After attenuationof the beam by insertion of the grid, the apparatus shall continue to operate and shall not generate inhibitionor fault signals. Although attenuation may produce a more noisy reading, any change in the mean measuredvalue of the integral gas concentration on inserting the grid shall not exceed 7.5% of the initial measuredvalue.

4.22 Environmental Ratings

The effects of the tests required to verify the apparatuss suitability for specified locations (dust, rain,hosedown, corrosion tests, etc.) Cells as described in 4.4.1, filled to atmospheric pressure with dry clean airshall be introduced and record. Introduce the required test. The apparatus shall not give any false alarms duringthe test. When tested with clean air and the initial calibration mixture, the reading shall be accurate within7.5% of full-scale gas concentration after this test. In lieu of the test criteria above, apparatus incorporatingalarms only shall be actuated by a 24 to 26% the full scale but not be actuated by a 14 to 16% the full scaleafter this test.

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4.23 Long Term Stability

The test shall be performed as for short-term drift, see 4.8, the measurements shall be made at intervals ofapproximately one week over a period of 1 month. During each measurement the ambient temperature afterstabilization shall be as specified in 4.4.9. The recorded readings shall comply with the performance require-ments defined in subsequent parts of this standard. The measured values of the integral concentration for eachgas shall not differ from the nominal values by more than 7% of the measuring range or 14% of the initialmeasured value, whichever is greater.

5. OPERATIONS REQUIREMENTSA quality assurance program is required to assure that subsequent open path gas monitors produced by themanufacturer shall present the same quality and reliability as the specific open path gas monitors examined.Design quality, conformance to design, and performance are the areas of primary concern.

Design quality is determined during the examination and tests, and is documented in the Certification Report.

Continued conformance to this standard is verified by audits of the facilities and procedures.

Quality of performance is determined by field performance and by periodic re-examination and testing.

5.1 Demonstrated Quality Control Program

5.1.1 The manufacturer shall demonstrate a quality assurance program which specifies controls for at least thefollowing areas: existence of corporate quality assurance guidelines; incoming quality assurance, including testing; in-process quality assurance, including testing; final inspection and tests; equipment calibration; drawing and change control; packaging and shipping; and handling and disposition of non-conforming materials.

5.1.2 Documentation/ManualThere should be an authoritative collection of procedures/policies. It should provide an accuratedescription of the quality management system while serving as a permanent reference for implementationand maintenance of that system. The system should require that sufficient records are maintained todemonstrate achievement of the required quality and verify operation of the quality system.

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5.1.3 RecordsTo assure adequate traceability of materials and products, the manufacturer shall maintain a record of allquality assurance tests performed, for a minimum period of two years from the date of manufacture.

5.1.4 Drawing and Change Control The manufacturer shall establish a system of product configuration control that shall allow no

unauthorized changes to the product. Changes to critical documents, identified in the CertificationReport, must be reported to, and authorized by, the certification agency prior to implementation forproduction.

The manufacturer shall assign an appropriate person or group to be responsible for, and require that,proposed changes to Listed or labeled or listed products be reported to the certification agency beforeimplementation.

Records of all revisions to all listed or labeled products shall be maintained.

5.2 Facilities and Procedures Audit

5.2.1 An audit of the manufacturing facility is part of the Certification investigation to verify implementationof the quality assurance program. Its purpose is to determine that the manufacturers equipment, proce-dures, and quality program are maintained to insure a uniform product consistent with that which wastested and Listed or labeled.

5.2.2 These audits shall be conducted periodically but at least annually by the certification agency or itsrepresentatives.

5.2.3 Listed or labeled products or services shall be produced or provided at or from the location(s) audited bythe certification agency and as specified in the Certification Report. Manufacture of products bearing theCertification Mark is not permitted at any other location without prior written authorization by thecertification agency.

5.3 Installation Inspections

Field inspections may be conducted to review an installation. The inspections are conducted to assess ease ofapplication, and conformance to written specifications. When more than one application technique is used, oneor all may be inspected at the discretion of the certification agency.

5.4 Manufacturers Responsibilities

The manufacturer shall notify the certification agency of changes in product construction, components, rawmaterials, physical characteristics, coatings, component formulation or quality assurance procedures prior toimplementation.

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APPENDIX A

Open Path Monitor Figures

Figure 1.1 The three Open Path Monitors shown in Figure 1.1 details how three gas clouds with different size and concentrationwould result in the same reading of 1 LFL m.

Figure 1.2 The Open Path Monitor shown in Figure 1.2 details how three gas clouds with different size and concentration wouldresult in the same reading of 5 %LFL(Avg).

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APPENDIX B

Units of MeasurementLENGTH: in. - inches; (mm - millimeters)

mm = in. 25.4

ft - feet; (m - meters)m = ft 0.3048

AREA: in2 - square inches; (mm2 - square millimeters)mm2 = in2 6.4516 102

ft2 - square feet; (m2 - square meters)m2 = ft2 0.0929

MASS: lb - pounds; (kg - kilograms)kg = lb 0.454

PRESSURE: psi - pounds per square inch; (bar - bar)kPa = psi 6.895

bar - bar; (kPa - kilopascals)bar = kPa 0.01bar = psi 0.06895

HEAT: Btu - British thermal units; (J - joules)J = Btu 1.0551 103

HEAT RELEASE RATE: Btu/min - British thermal units per minute; (kW - kilowatts)kW = Btu/min 0.0176

TEMPERATURE: F - degrees Fahrenheit; (C - degrees Celsius)C = (F - 32) 0.556

FLOW RATE: gal/min - gallon per minute; (L/min - liters per minute)L/min = gal/min 3.785

FLOW RATE: lpm - liters per minute ft3/min (cubic feet per minute) = lpm 0.035315

VELOCITY: m/s - meters per second ft/s (feet per second) = m/s 3.2808

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1. SCOPE 2. DEFINITIONS 3. GENERAL REQUIREMENTS 3.1 Review of Documentation 3.2 Markings 3.3 Manufacturers Installation and Operation Manuals 3.4 Construction and Functions 3.5 Test Equipment Calibration

4. PERFORMANCE REQUIREMENTS 4.1 General 4.2 Samples and Sequence 4.3 Preparation of Apparatus 4.4 Conditions for Test and Test Area 4.5 Un-Powered Preconditioning Storage 4.6 Vibration 4.7 Calibration 4.8 Accuracy 4.9 Trouble Signals 4.10 Temperature 4.11 Time of Response 4.12 Solar Radiation 4.13 Power Supply Variations 4.14 Power Supply Interruptions and Transients 4.15 Recovery from Power Supply Interruption 4.16 Electromagnetic Interference (EMI) 4.17 Partial Obscuration 4.18 Simulated Fog/Mist (Intended for Outdoor Use) 4.19 Water Vapor Interference 4.20 Beam Blockage Fault 4.21 Long Range Operation 4.22 Environmental Ratings 4.23 Long Term Stability

5. OPERATIONS REQUIREMENTS 5.1 Demonstrated Quality Control Program 5.2 Facilities and Procedures Audit 5.3 Installation Inspections 5.4 Manufacturers Responsibilities

APPENDIX A: Open Path Monitor Figures APPENDIX B: Units of Measurement