The MQ-7 gas sensor is SnO2, which with lower conductivity in clean air. It make detection by method of cycle high and low temperature, and detect CO when low temperature (heated by 1.5V). The sensor’s conductivity is higher along with the gas concentration rising. When high temperature (heated by 5.0V), it cleans the other gases adsorbed under low temperature. Please use simple electro circuit, Convert change of conductivity to correspond output signal of gas concentration. Good sensitivity to Combustible gas in wide range High sensitivity to Natural gas Long life and low cost Simple drive circuit MQ-7 gas sensor has high sensitivity to Carbon Monoxide. The sensor could be used to detect different gases contains CO, it is with low cost and suitable for different application. Technical parameters: Power supply needs: 5V Interface type: Analog Pin Definition: 1-Output 2-GND 3-VCC High sensitivity to carbon monoxide.