MQ3 Gas Sensor is another one of MQ family of gas sensors which is used to detect the alcohol content from 0.05 mg/L to 10 mg/L. It has a sensing element made of Tin Dioxide (SnO2) which has lower conductivity in clean air but when it comes in contact with alcohol gases the conductivity increases in proportion to the concentration of alcohol present. Thus, this Alcohol Sensor  is a low cost solution to measure the alcohol level, also it is resistant to the disturbances caused by the gasoline, vapour and smoke. The sensor has Analog output corresponding to the concentration of the Alcohol gas present or you can also get Digital Output for a particular concentration using the onboard potentiometer. This module can be used as a portable alcohol detector, Gas level over limit alarm, Breathalyser etc.