The MQ-9 combustible gas sensor module is a device that is used to detect the presence of combustible gases in the air. It is designed to be sensitive to a wide range of combustible gases, including carbon monoxide, methane, and LPG (liquefied petroleum gas). The module consists of a sensor element and a signal processing circuit that is used to interpret the output of the sensor and provide an indication of the gas concentration in the air.

This type of module is often used in gas leak detection systems, air quality monitoring systems, and other applications where it is necessary to detect the presence of combustible gases. It is typically connected to an electronic circuit or microcontroller, which can interpret the sensor's output signal and provide an indication of the gas concentration in the air. The module may also have additional features, such as alarms or control outputs, that can be used to take appropriate action in response to the presence of combustible gases.

The Analog CO/Combustible Gas Sensor(MQ9) module is useful for gas leakage detecting, it used the sensitive material SnO2, which with lower conductivity in clean air. It make detection by method of cycle high and low temperature, and detect CO when low temperature (heated by 1.5V). The sensors conductivity is more higher along with the gas concentration rising. When high temperature (heated by 5.0V), it detects Methane, Propane etc combustible gas and cleans the other gases adsorbed under low temperature. MQ-9 gas sensor has high sensitity to Carbon Monoxide, Methane and LPG. The sensor could be used to detect different gases contains CO and combustible gases, it is with low cost and suitable for different application.