A non-dispersive infrared（ NDIR） sensor for methane

carbon dioxide and carbon monoxide

which integrates infrared light source and detectors in optical gas chamber. In design of gas chamber

the height of gas chamber is determined as 25 mm

then

through calculation and software simulation analysis

the radius of gas chamber is determined as 10 mm. The sensor is tested after peripheral circuits have been designed

as demonstrated in the experiments

range of detection on methane

carbon monoxide and carbon dioxide can reach（ 0

40 000） × 10- 6.