MQ-9 is a Carbon Monoxide, Methane, and LPG Gas Sensor Module can be used to sense Carbon Monoxide and Methane Gas. Sensitive material of the MQ9 gas sensor is SnO2, which with lower conductivity in clean air.
It makes detection by the method of cycle high and low temperature, and detect CO when the low temperature (heated by 1.5V). The sensor’s conductivity is higher along with the gas concentration rising.
When a high temperature (heated by 5.0V), it detects Methane, Propane, etc. combustible gas and cleans the other gases adsorbed under low temperature.