Because in reality, most of the gases encountered in safety and health are mixtures of organic and inorganic gases. It is just for various reasons that our current understanding of toxic and harmful gases is more focused on combustible gases, gases that can cause acute poisoning (hydrogen sulfide, hydrocyanic acid, etc.), and some common toxic gases (carbon monoxide), Therefore, this article will first focus on these types of detectors and put forward suggestions on the application of various toxic and harmful (inorganic/organic) toxic gas detectors based on the current situation. Classification and principle of toxic gas detector: The key component of the gas detector is the probe. According to the hazards, we divide toxic and harmful gases into two categories: combustible gas and toxic gas. Because of their different nature and hazards, their detection methods are also different. Combustible gas is the most dangerous gas encountered in industrial occasions such as petrochemical industry. It is mainly organic gases such as alkanes and certain inorganic gases such as carbon monoxide. The combustible gas explosion must meet certain conditions, that is: a certain concentration of combustible gas, a certain amount of oxygen and enough heat to ignite their source of fire. These are the three elements of explosion, one is indispensable, that is, the lack of any one of them The conditions will not cause fire and explosion. When combustible gas (steam, dust) and oxygen are mixed and reach a certain concentration, it will explode when encountering a fire source with a certain temperature. We call the concentration of combustible gas that explodes when it encounters a fire source as the explosive concentration limit, or explosive limit for short, generally expressed in %. In fact, this kind of mixture does not explode in any mixing ratio and needs a concentration range.