The MQ5 Gas Sensor module is useful for gas leakage detecting. It can detect LPG, i-butane, methane, alcohol, Hydrogen, smoke and so on. The sensitivity can be adjusted using the on-board potentiometer, and you'd use this sensor by reading the analog pin to which it is connected. Please use these sensors only in controlled experiments! Combustible gases and fumes are very dangerous! Here are details for some MQ gas sensor.