This is a simple-to-use compressed natural gas (CNG) sensor, suitable for sensing  natural gas (composed of mostly Methane [CH4]) concentrations in the air.
The MQ-4 can detect natural gas concentrations anywhere from 200 to 10000ppm.
 

This sensor has a high sensitivity and fast response time.
The sensor's output is an analog resistance.
The drive circuit is very simple; all you need to do is power the heater coil with 5V, add a load resistance, and connect the output to an ADC.
 

This sensor comes in a package similar to our MQ-3 alcohol sensor, and can be used with the breakout board below.

 

Documents:

• Datasheet
• Wiring Example