MQ-2 gas sensor sensitive material used in the clean air low conductivity tin oxide (SnO2). When there is the environment in which the combustible gas sensor, conductivity sensor with increasing concentration of combustible gases in air increases. Using a simple circuit to convert the change in conductivity of the gas concentration corresponding to the output signal. MQ-2 gas sensor high on gas, propane, hydrogen sensitivity of detection of natural gas and other flammable vapors are also very good. This sensor can detect a variety of flammable gas, is a low-cost sensors for a variety of applications.