ST-48 Combustible/Toxic Gas Monitor

Item #: ST-48


Product Summary

The ST-48 Combustible/Toxic Gas Monitor is ideal for facilities that require continuous monitoring of toxic or combustible gases in hazardous areas. The enclosure is specifically designed to prevent an explosion. The monitor is well-suited for environments such as refineries, wastewater treatment, parking garages, laboratories, pharmaceutical, research and development, natural gas locations, the oil and gas industry, and any locations where toxic or combustible gases are present.


  • Dual Sensor Capability
  • Non-Intrusive One-man Calibration
  • Ex Proof Enclosure Class 1, Div 1 & 2, Groups A, B, C, & D
  • Local Digital Display with Bargraph & Trending
  • User Adjustable Dual Alarm Relays
  • 4-20 mA Analog Output
  • RS-480 Modbus Optional
  • NRTL CSA Approvals, ATEX Optional

The instrument’s fault supervision circuitry continuously monitors for failed sensor cell and communication line breaks. Plus sensor cell operation is continuously supervised 24/7 and when used in conjunction with distributive control systems or PLCs, provides immediate fault identification for a disconnected sensor cell.

The ST-48 is housed in a NEMA 7 explosion-proof enclosure suitable for Class 1, Division 1 and 2, Groups A, B, C, and D. The monitor can be used to detect Carbon Monoxide, IPA, Hydrogen, Hydrogen Sulfide, Ethanol, Propane, and other toxic gases. Capable of monitoring ppm levels of toxic gas or % LEL levels of combustible gases, the ST-48 is a perfect monitoring solution for providing worker protection in chemical plants, refineries, and other areas requiring hazardous classifications.

Sampling Method Diffusion
Gases Detected¹ Carbon Monoxide (CO)
Ethyl Acetate (C4H8O2)
Hydrogen Sulfide (H2S)
Isopropyl alcohol (IPA)
Methane (CH4)
Accuracy ± 10 % of Reading
Operating Temperature -40 to +50 ºC
-40 to +122 ºF
Display 68 x 128 pix LCD Displays 30-min Trend, Bargraph & 0.6″ Concentration Data
Sensor Type Disposable Electrochemical or LEL Catalytic Bead
Sensor Life 2 to 5 years under Normal Conditions
Signal Outputs 4-20 mA analog output
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 lbs
2.1 kg
Enclosure Stainless Steel
Optional Extras Alarm Output: 3ea. Alarm Relays: Low and High-Level Gas Alarm and System Fault
Signal Output: RS-485 Modbus Digital Communications
Country of Origin USA
Harmonized Tariff Code 8531.10.0045

1 Contact PureAire Monitoring for additional gases

One or Two Gas Monitoring
The PureAire ST-48 electronics are capable of monitoring one gas or two different individual gases simultaneously with one transmitter. The Dual Sensor Configuration displays two-gas readings and outputs 4-20 mA outputs for each gas to remote controllers.

ST-48 Combustible/Toxic Gas Monitor Literature

St-48 Combustible/Toxic Gas Monitor Manual

Air Check Ex Dual Gas with Relays 

Gases Detected with PureAire Monitors


Horn/Strobe Image

Remote Digital Display LEL 99185

99185 Remote Display LEL

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