The MQ-2 is a flammable gas like LPG, Butane, Hydrogen, and smoke detector or sensor or the MQ-2 gas sensor is sensitive to LPG, i-butane, propane, methane, alcohol, Hydrogen and smoke. This sensor detects the concentrations of combustible gas in the air and gives the reading as an analog voltage and it can measure concentrations of flammable gas of 300 to 10,000 pp. It finds application in gas leakage detecting equipment in houses and industry and a portable gas detector.