Mainly using gas sensors to detect the types of gases present in the environment, gas sensors are sensors used to detect the composition and content of gases. It is generally believed that the definition of gas sensors is based on the classification of detection targets, which means that any sensor used to detect gas composition and concentration is called a gas sensor, regardless of whether it uses physical or chemical methods. For example, sensors that detect gas flow are not considered gas sensors, but thermal conductivity gas analyzers are important gas sensors, although they sometimes use generally consistent detection principles. A gas analyzer is a process analysis instrument used to measure the composition of gases. Commonly used gas analyzers include thermal conductivity gas analyzers, electrochemical gas analyzers, and infrared absorption analyzers.