Product description:

• Sensitive material of MQ-9 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 more higher along with the gas concentration rising. When high
  temperature (heated by 5.0V), it detects Methane, Propane etc combustible gas and cleans the other
  gases adsorbed under low temperature. Please use simple electrocircuit, Convert change of conductivity
  to correspond output signal of gas concentration.
• MQ-9 gas sensor has high sensitity to Carbon Monoxide, Methane and LPG. The sensor could be
  used to detect different gases contains CO and combustible gases, it is with low cost and suitable for
  different application.

Features:

• Good sensitivity to CO/Combustible gas
• High sensitivity to Methane, Propane and CO
• Long life and low cost
• Simple drive circuit

Application:

• Domestic gas leakage detector
• Industrial gas detector
• Portable gas detector