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Model PT295 Series Toxic & Oxygen Deficiency

Trust PemTech's gas sensors to detect toxic gases in the air and depleted levels of oxygen. Our Model PT295 Series is a 24 VDC powered toxic gas detector consists of an interface module in a flame proof instrument enclosure and a 316 Stainless Steel sensor head assembly. The detectors monitor a variety of toxic gases in parts per million (ppm) range, including: ammonia, carbon monoxide, chlorine, chlorine dioxide, hydrogen, hydrogen chloride, hydrogen sulfide, nitric oxide, nitrogen dioxide, oxygen deficiency, and sulfur dioxide

The interface module is microprocessor-based electronic assembly with analog and digital circuitry to process the sensor signal for control, data display and to transmit the signal to a Gas Control Panel or to a PLC. In addition, PT295 Series detector includes a fully programmable form “C” type alarm relay contact that can be used to interface audio / visual alarm devices.

View Data Sheet   Technical Specifications

Fixed Gas Sensor Applications

  • Drilling Rigs
  • Offshore Platforms
  • Petrochemical Industry
  • Chemical Storage
  • Water & Wastewater Treatment
  • LPG Storage
  • Refineries

Key Toxic & Oxygen Deficiency Sensor Features

  • 3-Digit LED display
  • Simple one person auto Calibration
  • Fully programmable alarm relay
  • Linear 4-20mA Output
  • Wide Power input range
  • Reverse Polarity protection
  • Provides complete status & control capability in the control room

Technical Specifications

Sensor Type

Electrochemical Cell

Measuring Range

Ammonia (NH3) 0-50 ppm
Carbon Monoxide (CO) 0-100, 0-1000 ppm
Chlorine (CL2) 0-10 ppm
Chlorine Dioxide (CLO2) 0-50 ppm
Ethylene (C2H4) 0-100 ppm
Ethylene Oxide (C2H4O) 0-50 ppm
Hydrogen Chloride (HCL) 0-20 ppm
Hydrogen Sulfide (H2S) 0-100, 0-500 ppm
Hydrogen (H2) 0-200 ppm
Methyl Mercaptan (CH3SH) 0-100 ppm
Nitrogen Dioxide (NO2) 0-20 ppm
Nitric Oxide (NO) 0-100 ppm
Oxygen Deficiency (O2) 0-25 %(volume)
Sulfur Dioxide (SO2) 0-100 ppm


± 2 ppm or ± 10% of reading, whichever is greater.

Zero Drift

< 5% per year

Response Time

CO, H2, H2S, NO2 T90 < 30 s
NO, SO2 T90 < 15 s
NH3 T90 < 60 s
O2 T90 < 15 s

Electrical Classifications

Explosion Proof Enclosure

CSA: Class I, Div 1 & 2, Groups B, C & D
C22.2 No 30-M1985 &
C22.2 No 142-M1987


CSA,  ABS Type Approved


EN 60079-1:2014 II 2G db IIC T6 Gb

Operating Temperature Range

H2S, H2, SO2 & CO:

-40°F to +149°F (-40°C to +65°C)  (intermittent)

All others:

-30°F to +131°F (-34°C to +55°C)

Humidity Range

5% to 95%  RH (non condensing) 

Storage Temperature

Electronics Interface Module:
  -40°F to +185°F (-40°C to +85°C)

Sensor Head Assembly:
  32°F to +68°F (0°C to +20°C) (Cell)


Height: 7.4 inches (188 mm)
Width: 6.2 inches (159 mm)
Depth: 4.9 inches (125 mm)

Ingress Protection


Display and Indicators

3 Digit LED display
Displays Alarm and Fault Status

Power Input

12- 28 VDC (24 VDC Nominal)

Power Consumption

< 1 Watt

Alarm Relays

Programmable Alarm Relay Contacts
  SPDT Form "C" Relay
  5 A @ 250 VAC or 30 VDC

Analog Output

Linear 4-20 mA output

  Fault: 0 mA
  Calibrate Mode: 2 mA
  Over Range: > 21 mA

Input / Output Protection

  • Transient over voltage suppressor
  • Reverse Polarity protection
  • EMI / RFI Immunity

Cable Requirement

Three wire shielded cable for power and analog signal.

Max of 300 Ω load for analog output


Dust or Splash guard, Flow Adapter with tube fittings, Sensor Duct Mount Kit, Pole Mount brackets.

Cable Entry

3/4" NPT Female Adapter available for 1/2” NPT or M20


Two year Electronics

One year Sensor head assembly (cell)


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