This is a simple-to-use Carbon Monoxide (CO) sensor, suitable for sensing CO concentrations in the air. The MQ-7 can detect CO concentrations anywhere from 20 to 2000ppm.
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.
Documents:
Datasheet
Wiring Example