MST137 gas sensor is a methane gas sensor. The gas sensitive material used by the sensor is tin dioxide (SnO2), which has a low conductivity in clean air. When combustible gas exists in the environment of the sensor, the conductivity of the sensor increases with the increase of combustible gas concentration in the air. A simple circuit is used to convert the change in conductivity into an output signal corresponding to the concentration of the gas.

MST137 CH4 sensor