This is a simple-to-use Carbon Monoxide (CO) sensor, suitable for sensing CO concentrations in the air. The module utilizes an MQ-7 sensor as the sensitive component and has a protection resistor and an adjustable resistor on board. The MQ-7 can detect CO-gas concentrations anywhere from 100 to 1000ppm. This sensor has a high sensitivity and fast response time. The module's output is either analog or TTL level.