HJ 872-2017 "Electrochemical sensor law for emergency monitoring of toxic and harmful gases such as environment air and chlorine gas" stipulates the method of using Electrochemical sensor to determine nine harmful gases such as chlorine, hydrogen sulfide, hydrogen chloride, carbon monoxide, hydrogen cyanide, phosgene, hydrogen fluoride, ammonia and sulfur dioxide in environment air. This standard is applicable to on-site emergency monitoring, screening and census in environment monitoring, and provides technical support for emergency treatment of related environment events. Electrochemical sensor uses the electrochemical activity of the target to generate an electrical signal proportional to its concentration to achieve qualitative semi-quantitative analysis of the concentration of toxic and harmful gases.