ST-48 Hydrogen Sulfide Combustible Gas Monitor 0-30 ppm

ST-48 Hydrogen Sulfide Combustible Gas Monitor 0-30 ppm

Item #: 95122


Product Summary

The ST-48 Combustible Gas Monitor is ideal for facilities that require continuous monitoring of hydrogen sulfide. The enclosure is specifically designed to prevent an explosion. The monitor is well suited for environments such as refineries, natural gas locations, wastewater treatment plants, chemical plants, and any locations requiring LEL gas monitoring for combustible gases. The monitor is housed in a NEMA 4 explosion-proof enclosure suitable for Class 1, Group B, C, and D, Class 2, Group E, F, and G. PureAire’s durable, long-life LEL catalytic sensor will last 5-6  years in a normal environment without needing to be replaced.


  • LEL Combustible Gas Analyzer with 0-100% or 0-4% of LEL
  • Designed for Combustible Gases including Hydrogen Sulfide
  • Gas Sampling for Vessels or General Safety with Wall Mount
  • Explosion-Proof Enclosure
  • Non-Intrusive Calibration
  • Local Digital Display
  • 4-20 mA Analog Output
  • 2 Configurable High/Low Relays
  • Long Life LEL Catalytic Sensor Average, 5-6 years

The ST-48 LEL gas detector is housed in a NEMA 4 Explosion Proof Enclosure and is available for hydrogen sulfide (H2S). Capable of monitoring the percentage of LEL combustible gas, the ST-48 is a perfect monitoring solution for providing worker protection in natural gas locations, paper mills, wastewater treatment facilities, the oil and gas industry,  and other areas requiring hazardous monitoring for hydrogen sulfide.

The instrument’s fault supervision circuitry continuously monitors for failed sensor cell and communication. Our sensor cell operation is continuously supervised 24/7, and when used with distributive control systems or PLCs, the monitor provides immediate fault identification.


Sampling Method Diffusion Cell
Gases Detected¹ Hydrogen Sulfide (H2S)
Ethanol (C2H5OH)
Ethane (C2H6)
Ethyl Alcohol (C2H5OH)
Ethylene (C2H4)
Isopropyl alcohol (IPA)
Methyl Alcohol (MeOH)
Accuracy ± 1 % of Reading
Operating Temperature -32 to +50 ºC
-25 to +122 ºF
Display 3 1/2″ Digit LCD Digital Display
Sensor Type LEL Catalytic Bead
Sensor Life 2 to 5 years under Normal Conditions
Signal Outputs 2 alarm relays, 4-20 mA analog output, and fault relay
Power Requirements  24 VDC
95 mA
Width 5.12 in
130.05 mm
Height 5.0 in
127 mm
Depth 8.0 in
203.2 mm
Weight 4.7 lb
Enclosure NEMA 4 Explosion Proof Suitable for Class 1, Group B, C, & D

1 Contact PureAire for more gases

Additional LEL Monitor Accessories List Price
8 Channel Controller $3,355.00 US (P/N # 99196)
Horn and Strobe  $190.00 US (P/N # 42002)
Remote Display $435.00 US (P/N # 99185)

Self-Supervised Operation
The PureAire ST-48 Hydrogen Sulfide Combustible Gas Monitor incorporates sophisticated electronics that, when used in conjunction with distributive control systems or PLCs enable you to quickly identify and correct major system faults. These enhanced self-diagnostic capabilities include missing cell and broken transmitter wiring. Should a system error occur, the ST-48 Combustible Gas Monitor outputs a 4-20 mA signal to remote alarm/control systems to immediately alert control room personnel.

ST-48 Hydrogen Sulfide Combustible Gas Monitor Literature

ST-48 Combustible/Toxic Gas Monitor Literature

ST-48 Manual 

Gases Detected with PureAire Monitors

LEL Combustibles Layout 

LEL Monitor Layout 

LEL Monitor with Fan Relay 


Horn/Strobe 42002

Remote Digital Display LEL 99185

Remote Digital Display LEL 99185


8-Channel Controller for Oxygen, Carbon Dioxide, or Toxic/Combustible Gas Monitors