MQ series gas sensors are used to detect different gas concentration in air. MQ-5 sensor is used in gas leakage detecting equipment in House and industry, are suitable for detecting of LPG, natural gas , town gas, avoid the noise of alcohol and cooking fumes and cigarette smoke. MQ-5 sensor requires 5V AC or DC. Two pins are for heater coil, and other four are for fetching signals. Output of MQ5 sensor is analog. Higher the gas concentration, higher the output voltage at signal pins.