NEC1 AREA ELECTRICAL CLASS All semi-enclosed and enclosed process areas in the collection system and processing areas are classified as Class I, Division 1 or Division 2, Group D. The hazards are leakage and ignition of the sewage gases and potential ignition of floating flammable liquids. Ventilation of an area may reduce classification to Division 2 or not classified. Distance from process equipment may reduce or eliminate hazardous classification. Consult Article 500 of the NEC and NFPA 4962 for more information. GAS DETECTION REQUIREMENTS Combustible Gas Detection is required by NFPA 820 in many areas of the collection system and processing plants. Hydrogen Sulfide and Oxygen monitoring may also be required depending on the influent characteristics, persistence in the mains and whether or not the area is enclosed and or ventilated. Methane Gas Sensors are placed within 12 inches of the roof of a structure. When Oxygen deficiency and Hydrogen Sulfide are monitored, the sensors are usually placed in the breathing zone (4 to 6 foot elevation). NFPA 820 requirements and the need for toxic and Oxygen deficiency monitoring are summarized below.

FROM NFPA 5-4.4 - Combustible gas detection equipment located in hazardous (classified) locations, as defined in accordance with NFPA 70, National Electrical Code, shall be listed for use in such atmospheres. The detectors shall be set to alarm at 10 percent of the lower explosive limit (LEL) in accordance with the makers’ calibration instructions and shall be connected to alarm signaling systems.Exception: Alarm limits shall be permitted to be set at a higher percentage of the explosive limit where experience indicates ambient levels are too high and spurious alarms are probable. ANNUNCIATION Visual and audible alarms shall be provided at the entrance to all hazardous classified areas, within such spaces, local work areas and remote for supervisoryCommunication.31 NEC: NFPA 70, National Electrical Code2 Article 500 of NFPA 70 and NFPA 496, Standard for Purged and Pressurized Enclosures

COLLECTION SYSTEM AND LIQUIDS TREATMENT GAS DETECTION 3, 4

PROCESSAREA

AREACLASS A HAZARDSS STRATEGY

Storm Water Wet Well

Division 2 If Enclosed

LEL (Methane) LEL (Floating

Hydrocarbons) Sample Draw from Headspace and near Liquid Surface

Install Interior, Exterior & Remote Annunciation

Combined or Sanitary Wet Well

Division 2 If Enclosed (2) LEL, H2S, O2

Sample Draw from Headspace and near Liquid Surface Interior, Exterior & Remote Annunciation

Sewage Pumping Station Wet Well

Division 1 or Division 2 (2) LEL, H2S, O2

Sample Draw Interior, Exterior & Remote Annunciation

Odor Control Areas Division 2 LEL, FDS Ambient Monitoring, Observe Sensor Placement Guide Interior, Exterior & Remote Annunciation

Screen Facilities Division 1 or Division 2 (2) LEL, H2S, O2

Ambient Monitoring Interior, Exterior & Remote Annunciation

Flow Equalization Areas

Division 1 or Division 2 LEL Ambient Monitoring

Interior, Exterior & Remote Annunciation

Grit Removal Division 1 or Division 2 (2) LEL, H2S, O2

Ambient Monitoring Interior, Exterior & Remote Annunciation

Aeration Sedimentation

Division 1 or Division 2 (2) LEL, H2S, O2

Ambient Monitoring Interior, Exterior & Remote Annunciation

Oxygen Aeration Division 2 LEL Ambient Monitoring Interior, Exterior & Remote Annunciation

Breakpoint Disinfection Unclassified Cl2, Ozone, NH3

Ambient Monitoring Interior, Exterior & Remote Annunciation

Ammonia Stripping Unclassified NH3, Other Ambient Monitoring Interior, Exterior & Remote Annunciation

Notes: a All are Class I, Group D. b Fire Detection denoted by FDS.

SOLIDS TREATMENT PROCESS GAS DETECTION 5, 6

PROCESSAREA

AREACLASS A YGETARTS SDRAZAH

Scum Handling, Pits, Other Areas

Division 1 or Division 2 LEL (Methane) Sample Draw from Headspace and near Liquid Surface

Install Interior, Exterior & Remote Annunciation

Clarifier Division 1 or Division 2 LEL, O2

Sample Draw from Headspace and near Liquid Surface Install Interior, Exterior & Remote Annunciation

Sludge Pumping Dry Wells

Division 1 or Division 2 LEL, O2

Ambient Monitoring Interior, Exterior & Remote Annunciation

Other Sludge Processes

Division 1 or Division 2 LEL, O2

Ambient Monitoring Local & Remote Annunciation

Anaerobic Digesters &

Process Areas Division 1 or

Division 2 LEL, O2Ambient Monitoring

Local & Remote Annunciation

Enclosed Areas, Galleries, Tunnels

Division 1 or Division 2 LEL, O2, FDS Ambient Monitoring

Local & Remote Annunciation Aerobic sludge

reduction Division 2 NH3, FDS Ambient Monitoring Local & Remote Annunciation

Digester Gas Processing

Division 1 or Division 2 LEL Ambient Monitoring

Local & Remote Annunciation

Chlorine Oxidation Unclassified Cl2 Ambient Monitoring Local & Remote Annunciation

Notes: a All are Class I, Group D. b Fire Detection denoted by FDS.

3 NFPA 820, Standard for Fire Protection in Wastewater Treatment and Collection Facilities, Tables 2-2, 3-2, and 4-2(a) 4 29 CFR 1910.1000, Table Z1; PEL (Permissible Exposure Limits) expressed as an 8 hour TWA (Time Weighted Average) 5 NFPA 820, Standard for Fire Protection in Wastewater Treatment and Collection Facilities, Tables 2-2, 3-2, and 4-2(a) 6 29 CFR 1910.1000, Table Z1; PEL (Permissible Exposure Limits) expressed as an 8 hour TWA (Time Weighted Average)

PROCESS AREA

AREA CLASS A HAZARDSS STRATEGY

Storm Water Wet Well

Division 2 If Enclosed

LEL (Methane) LEL (Floating

Hydrocarbons) Sample Draw from Headspace and near Liquid Surface

Install Interior, Exterior & Remote Annunciation

Combined or Sanitary Wet Well

Division 2 If Enclosed (2) LEL, H2S, O2 Sample Draw from Headspace and near Liquid Surface

Interior, Exterior & Remote Annunciation

Sewage Pumping Station Wet Well

Division 1 or Division 2 (2) LEL, H2S, O2 Sample Draw

Interior, Exterior & Remote Annunciation

Odor Control Areas Division 2 LEL, FDS Ambient Monitoring, Observe Sensor Placement Guide Interior, Exterior & Remote Annunciation

Screen Facilities Division 1 or Division 2 (2) LEL, H2S, O2 Ambient Monitoring

Interior, Exterior & Remote Annunciation Flow

Equalization Areas Division 1 or

Division 2 LEL Ambient Monitoring Interior, Exterior & Remote Annunciation

Grit Removal Division 1 or Division 2 (2) LEL, H2S, O2 Ambient Monitoring

Interior, Exterior & Remote Annunciation Aeration

Sedimentation Division 1 or

Division 2 (2) LEL, H2S, O2 Ambient Monitoring Interior, Exterior & Remote Annunciation

Oxygen Aeration Division 2 LEL Ambient Monitoring Interior, Exterior & Remote Annunciation

Breakpoint Disinfection Unclassified Cl2, Ozone, NH3 Ambient Monitoring

Interior, Exterior & Remote Annunciation

Ammonia Stripping Unclassified NH3, Other Ambient Monitoring Interior, Exterior & Remote Annunciation

Notes: a All are Class I, Group D. b Fire Detection denoted by FDS.

PROCESS AREA

AREA CLASS A HAZARDS STRATEGY

Scum Handling, Pits, Other Areas

Division 1 or Division 2 LEL (Methane) Sample Draw from Headspace and near Liquid Surface

Install Interior, Exterior & Remote Annunciation

Clarifier Division 1 or Division 2 LEL, O2 Sample Draw from Headspace and near Liquid Surface

Install Interior, Exterior & Remote Annunciation Sludge Pumping

Dry Wells Division 1 or

Division 2 LEL, O2 Ambient Monitoring Interior, Exterior & Remote Annunciation

Other Sludge Processes

Division 1 or Division 2 LEL, O2 Ambient Monitoring

Local & Remote Annunciation Anaerobic

Digesters & Process Areas

Division 1 or Division 2 LEL, O2 Ambient Monitoring

Local & Remote Annunciation

Enclosed Areas, Galleries, Tunnels

Division 1 or Division 2 LEL, O2, FDS Ambient Monitoring

Local & Remote Annunciation Aerobic sludge

reduction Division 2 NH3, FDS Ambient Monitoring Local & Remote Annunciation

Digester Gas Processing

Division 1 or Division 2 LEL Ambient Monitoring

Local & Remote Annunciation

Chlorine Oxidation Unclassified Cl2 Ambient Monitoring Local & Remote Annunciation

Notes: a All are Class I, Group D. b Fire Detection denoted by FDS.

Gas Detection for Waste Treatment, Collection & ProcessingManufacturer’s Reprint

Pumped Sample-Draw, Flow Switch

& Filter

Division 2 Sensor Mounting Options

Remote Sensor (High or Low)

Standard Transmitter-Sensor

Assembly

2 or 3-Wire 4-20 mA Available

Description Product No.SensAlertPlus Transmitters 2-Wire GP ...................................820-0201-013-Wire GP ...................................820-0202-01 3-Wire GP, with I.S. Barrier ...........820-0202-043-Wire GP for use w/ relay card2 ...820-0202-032-Wire HD, Div2 ...........................820-0203-01 3-Wire HD, with I.S. Barrier ...........820-0204-04 3-Wire HD, Div2 Standard Dome ..820-0204-013-Wire HD, Div2 Large Dome2 .......820-0204-022-Wire XP, Div1 ...........................820-0205-013-Wire XP, Div1 Standard Dome ...820-0206-013-Wire XP, Div1 Large Dome2 ........820-0206-02

SensAlertPlus Sensors

H2S 100 ppm ...............................823--0206-21

SensAlertPlus AccessoriesType S TOD Cell .............................821-0204-06 Relay Card ....................................700-0046-01Moisture Barrier Assembly ............821-0201-01Calibration Cup ............................821-0202-01Rainshield ....................................821-0203-01Remote Sensor Kit for Div. 1 ..........821-0207-02Remote Sensor Kit for Div. 2 ..........821-0207-01Duct Mount Kit .............................821-0209-02Mounting Kit ................................821-0213-01

Gas Detection for Waste Treatment, Collection & ProcessingINTEGRATION STRATEGY Integrating a Process and Personnel protection gas detection system requires that the notification and control procedures mandated by Code and Law be followed, including Insurance Company mandates. Compliance with these issues is simplified by using a Sensidyne Controller to process the gas sensor inputs, provide annunciation and supervisory control. A 4-Channel System is illustrated below. Up to 16 gas sensors may be accommodated by one Controller.

GAS SENSOR MOUNTING CONFIGURATIONS Gas sensors are located in the breathing zone (4 to 6 feet above floor) for gases similar in density to air, including Oxygen deficiency. For lighter than air gases, (Methane, Ammonia

or Hydrogen), the sensors must be positioned within 12 inches of the ceiling or highest point of an enclosed area. Heavier than air gases like solvent vapors or Halocarbon refrigerants should have the sensors placed within 12 inches of the floor or lowest point in the enclosed area. Target gas density and potential leak sources should always be identified when configuring a gas detection system. Gas sensors are often mounted remotely from the transmitter, which is normally kept at eye level. These situations arise due to gas density variations or difficult access locations. Tubing is run to a calibration adapter on the sensor assembly, so that routine calibrations can be performed from the transmitter. Other configurations include duct mounting, and drawing a sample from a remote or inaccessible location. The latter has a flow switch to indicate sample system integrity, as required by Code. Careful attention to gas sensor placement, supervisory control functions and emergency response planning will produce a functional, accountable and low maintenance area monitoring system which complies with local codes and laws.

PPM HYDROGEN INTERFERENT TABLE Gas Exposure Response

Carbon Monoxide 5 ppm +1 ppm Chlorine 1 ppm None Ethylene 1.3 ppm +1 ppm Hydrogen Chloride 5 ppm None Hydrogen Cyanide 3 ppm +1 ppm Nitric Oxide 4 ppm +1 ppm Nitrogen Dioxide 5 ppm None Sulfur Dioxide 5 ppm None

CO SENSOR INTERFERENT TABLEGas Exposure Response

Chlorine 1 ppm None Ethylene 1.3 ppm +1 ppm Hydrogen 1.7 ppm +1 ppm Hydrogen Chloride 5 ppm None Hydrogen Cyanide 5 ppm +1 ppm Hydrogen Sulfide 50 ppm +1 ppm Nitric Oxide 5 ppm +1 ppm Nitrogen Dioxide 5 ppm -1 ppm Sulfur Dioxide 5 ppm None

AMMONIA INTERFERENT TABLE Gas Exposure Response

Alcohols 1000 ppm None Carbon Dioxide 5000 ppm None Carbon Monoxide 100 ppm None Hydrocarbons % Range None Hydrogen 10,000 ppm None Hydrogen Sulfide 10 ppm +1 ppm

H2S SENSOR INTERFERENT TABLE

Gas Exposure Response Ammonia 100 ppm None Carbon Monoxide 50 ppm +1 ppm Chlorine 10 ppm -1 ppm Ethylene 100 ppm None Hydrogen 700 ppm +1 ppm Hydrogen Chloride 5 ppm None Hydrogen Cyanide 10 ppm None Nitric Oxide 35 ppm None Nitrogen Dioxide 5 ppm -1 ppm Sulfur Dioxide 5 ppm +1 ppm