The gas-sensing material used in the MQ-2 smoke sensor is tin dioxide (SnO2), which has a low conductivity in clean air. When there is flammable gas in the environment where the smoke sensor is located, the conductivity of the smoke sensor increases with the increase of the concentration of flammable gas in the air. The change in conductivity can be converted into an output signal corresponding to the gas concentration of this smoke sensor using a simple circuit.

The MQ-2 gas smoke sensor has high sensitivity to liquefied gas, propane, and hydrogen, and is also ideal for the detection of natural gas and other combustible vapors. This gas sensor can detect a variety of flammable gases and is a low-cost smoke sensor suitable for a variety of applications.