The MQ-2 module is a gas sensor used to detect the presence of flammable gases such as methane, butane, propane, and smoke. It operates on 5V and has two outputs: digital, which gives a signal when a certain limit is exceeded, and analog, which gives a value representing the gas concentration. The sensitivity can be adjusted via a variable resistor on the board. It is used in leak detection, alarm, and fire protection systems and is easily programmed with Arduino.

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