Abstract: As toxic and flammable gas alarms are used in safety protection in petroleum, chemical and other product manufacturers, the linearity, reliability and accuracy of their core sensors are important. Taking an electrochemical gas sensor for detecting carbon monoxide as an example, this paper presents its principles and overall working process, describes the function of its each component, and discusses its performance characteristics in various situations. Finally, the evaluation of the linearity, correlation, response time, and temperature and humidity dependence of the sensor is presented.