The MS400S portable composite gas detection alarm is used for portable and rapid detection of various gas concentrations, temperature and humidity measurements, and alarm for exceeding the standard. The MS400S composite four in one gas detector adopts a 231 inch high-definition color screen to display concentration in real time. The selected gas sensor mainly detects electrochemical, infrared, catalytic combustion, thermal conductivity, and PID photoionization principles. Advanced circuit design and mature kernel algorithm processing. MS400S 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. It can detect more than 500 types of gases