MQ-3 gas sensor is sensitive material used in clean air, low conductivity tin dioxide (SnO2). When the sensor is present in the environment in which the alcohol vapor , the sensor's conductivity increases with the concentration of alcohol gas in the air increases. Using a simple circuit can be converted to the change in conductivity of the gas concentration with the corresponding output signal. MQ-3 gas sensor with high sensitivity to alcohol , gasoline can resist , smoke , water vapor interference. This sensor can detect various concentrations of alcohol atmosphere , is a low-cost sensors for a variety of applications