MQ 6 Gas sensor is used as LPG, Butane and Propane Sensor to generate alarm when there is leakage of these gases from the source. MQ6 is a highly sensitive gas sensor to petroleum based gases but less sensitive to Alcohol and Carbon di oxide. This simple sensor can be installed in the kitchen to give warning alarm if there is leakage of LPG.
MQ6 gas sensor is a 6 pin device and it requires 5 volt DC maximum which is derived from a Zener based power supply. There is a heating element inside the sensor which becomes hot at 5 volt and remains stand by. When the sensor detects gas molecules between 100 ppm to 1000 ppm, in the atmosphere, its output turns high and triggers T1 to activate the buzzer. Red LED indicates the high output from the sensor.
Fix the unit 1-2 meters away from the burner or gas cylinder. Adjust VR1 for maximum sensitivity of gas. Place the sensor near the burner and just open the burner for few seconds and close without igniting. Adjust VR1 immediately to set the sensitivity.
See the working and Pin connection of Gas sensors in this link