Product information "Gravity: Analog Carbon Monoxide Sensor (MQ7) For Arduino"
This is an Arduino Carbon Monoxide Sensor. It uses MQ7 probe to detect Carbon Monoxide (CO) concentrations in the air from 20 to 2000ppm.
The sensitivity can be adjusted by the potentiometer. The output is proportional to the density of gas. You can use analog reading to read the data from this sensor.