This is a very easy to use low cost semiconductor Gas sensor Module with analog and digital output. This module uses MQ3 Alcohol gas sensor as a alcohol gas sensing element. It requires no external components just plug in Vcc & ground pins and you are ready to go.
For Digital output the threshold value can be easily set by an on-board potentiometer.  Using this module you can easily interface MQ3 Alcohol sensor to any Microcontroller, Arduino or even Raspberry Pi.
Since this Gas Sensor module is sensitive to alcohol it can be used in breathalyser. MQ3 Sensor also has small sensitivity to Benzine.
It is used for on-site detection of motor vehicle drivers and other workers
who are strictly prohibited from drinking. It is also used for detection of ethanol vapor in other places.
Features & Specifications:
Sensitive to alcohol, ethanol.
It has signal output indication.
dual-channel signal output (analog output and TTL level output).
TTL output effective signal is low level. (When the output signal light is on at low level, it can be directly connected to the single chip computer).
Analog output 0-5V voltage, the higher the concentration, the higher the voltage.
 It simplifies the interface to the odd pin spacing of the sensor and provides an interface through standard 4 x 0.1″ header pins.
It has high sensitivity and good selectivity to ethanol vapor.
An onboard LED signals the presence of any gas.
Long-term service life and reliable stability.
Fast Response Recovery Characteristics.
Size: 32mm X22mm X27mm long X wide X high
ain chips: LM393, ZYMQ-3 gas sensors
Working Voltage: DC 5 Volts