A gas detector uses different sensor technologies depending on the gas it must detect. Which sensor suits which gas, how long it lasts, and why periodic calibration is needed — explained by Ace Electronics, a gas detector manufacturer since 1993 and a KOLAS-accredited calibration laboratory.
Gas sensors are broadly catalytic-bead (combustible/LEL), electrochemical (toxic gases such as CO and H₂S, and oxygen), semiconductor (combustible, CO, VOC, etc.), and infrared/NDIR (CO₂ and hydrocarbons). All sensors drift over time, so periodic calibration corrects the error and the sensor is replaced at end of life.
Why there are different sensor types
Gases differ in their physical and chemical properties, so no single method detects them all accurately. The sensor type is chosen by whether the target gas is combustible or toxic and by its concentration range.
Four common sensor technologies
| Type | Principle | Target gas | Notes |
|---|---|---|---|
| Catalytic bead | Burns combustible gas on a catalyst; measures the heat (resistance change) | Combustible gas (LEL) | The LEL standard. Needs oxygen; watch for catalyst poisons (silicone, sulfur) |
| Electrochemical | Measures the current from the gas oxidizing/reducing at an electrode | Toxic gases (CO, H₂S, NH₃), oxygen | Precise at low ppm, good selectivity. Limited life (electrolyte) |
| Semiconductor | Measures resistance change as gas adsorbs on a metal-oxide surface | Combustible, CO, VOC, and more | Low-ppm sensing, long life, economical. Affected by humidity/selectivity |
| Infrared (NDIR) | Measures how much infrared at a specific wavelength the gas absorbs | CO₂, hydrocarbons, and more | Works without oxygen, no poisoning, long life. Cannot see hydrogen, etc. |
※ These are general characteristics; actual performance depends on the product spec and environment.
Sensors have a lifespan
Sensors are closer to consumables. Electrochemical cells deplete their electrolyte, catalytic beads degrade, and even semiconductor and infrared sensors shift over the long term. Harsh environments (heat, humidity, dust, corrosive gases, poison exposure) shorten their life.
That is why calibration matters
When sensitivity drifts, the detector reports a different value for the same gas concentration. Periodic calibration compares against standard gas to determine and correct this error, and reveals whether the sensor has reached its irreversible limit. Whatever the sensor type, calibration is essential to keep readings accurate. See the calibration cycle guide and portable calibration procedure.
To find the right sensing method for your site, browse our gas detectors, or tell us your target gas and environment and we will recommend one.
