Several gas detection technologies are used in combustible gas detectors. The most common are catalytic bead and infrared detectors.
Catalytic detector
A catalytic sensor uses temperature changes caused by a combustible gas reacting with oxygen to measure gas levels.
Infrared detector
An infrared sensor works on the principle that gas will absorb infrared radiation. There will be a sample cell and a reference cell, which are compared to determine the presence of gas.