MQ2 Gas Sensor

The MQ2 gas sensor can easily detect smoke, liquefied natural gas (LNG), butane, propane, methane, alcohol, and hydrogen in the air.

Working principle

The MQ-2 type smoke sensor is made of a tin dioxide semiconductor gas sensing material. When it works at a temperature of 200 to 300 °C, the tin dioxide adsorbs the oxygen in the air, which reduces the density of electrons on the semiconductor and thus increasing the resistance. When it comes into contact with smoke, if the barriers at grain boundaries are changed by the smoke, the conductivity on the surface is changed accordingly. In this way, smoke can be detected. A higher smoke density indicates a higher conductivity and lower output resistance.

Real-life example

  • A smoke alarm can detect smoke and flammable gas.


  • Dimensions: 24 × 36 (mm)
  • Operating current: 160 mA
  • Impedance when heated: 33Ω
  • Preheating energy consumption:< 800 mW


The detection error may be large when the module starts to work. The module can be preheated for five minutes for better performance.

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