The MS400 portable toxic and harmful gas detection alarm is used for portable and rapid detection of toxic and harmful gas concentration, temperature and humidity measurement, and alarm for exceeding the standard. Using a 2.31-inch high-definition color screen to display concentration in real time, imported brands (Honeywell, Nippon Genshin, CITY, Alpha, Dynament, Membrapor, etc.) gas sensors are selected. The main detection principles include electrochemistry, infrared, catalytic combustion, thermal conductivity, and PID photoionization. Advanced circuit design, mature kernel algorithm processing, and multiple software works have been obtained. MS400 can detect gas concentration in pipelines, confined spaces, and atmospheric environments. It can detect gas leaks or high concentration single gas purity with various background gases such as nitrogen or oxygen, and can detect more than 500 types of gases.