Flammable Gas & Smoke Sensor MQ-2

MQ-2 gas sensor detects the presence of combustible gas and smoke at concentrations from 300 to 10,000 ppm. The sensor’s simple analog voltage interface requires only one analog input pin from your microcontroller.
Connecting 5V across the heating (H) pins keeps the sensor hot enough to function correctly. Connecting 5V at either the A or B pins causes the sensor to emit an analog voltage on the other pins. A resistive load between the output pins and ground sets the sensitivity of the detector. The resistive load should be calibrated for your particular application using the equations in the datasheet, but a good starting value for the resistor is 20 kΩ.

Documents:

• MQ2 Datasheet
• Arduino Tutorial