Question

The flammable gas detector works on which of the following phenomena?

• A. Catalytic
• B. Paramagnetic
• C. Electrochemical
• D. Photoionisation

Hint:

Catalytic bead sensors are the industry standard for LEL (flammable gas) detection—they work by oxidizing the gas on a heated catalyst.

Answer 1

The Correct Option is A, D

Flammable gas detectors used in hydrocarbon detection mainly operate on the principle of catalytic oxidation.
A catalytic bead inside the sensor heats up when flammable gases contact its surface.
When oxidation occurs, heat is released, increasing the temperature and electrical resistance of the sensing element.
The detector interprets this resistance change as gas concentration.
Paramagnetic sensors measure oxygen only, so Option B is incorrect.
Electrochemical sensors detect toxic gases like CO or H₂S, not flammable gas, so Option C is incorrect.
Photoionization detectors (PID) detect VOCs with high ionization potential but do not measure flammability, so Option D is incorrect.
Thus, the correct operational principle is catalytic oxidation.