Gas sensor is the device used for detecting the presence of Gases like Carbon monoxide, LPG, Ethanol, Toluene, Hydrogen etc. These are used as safety measures in work places and Home to avoid hazardous situations. The sensor can be used to generate an alarm or to activate a system to shut down the gas flow. Gas detectors are usually battery operated devices and if the gas level exceeds the preset level, it sends output signal to activate the circuit. Most commonly used gas sensors are LPG sensor, Smoke sensor and Alcohol sensor used in Breath analyzer.