How to apply toxic and harmful gas detectors in industry?
In reality, many gases encountered in safety and health are mixtures of organic and inorganic gases. Due to various reasons, our current understanding of toxic and harmful gases is still more focused on combustible gases, gases that can cause acute poisoning (such as hydrogen sulfide and hydrogen cyanide), as well as some common toxic gas detectors (such as carbon monoxide) and oxygen. Therefore, this article will first focus on introducing these types of detectors and provide suggestions for the application of various toxic and harmful (inorganic/organic) gas detectors based on the current situation.
The classification of toxic and harmful gas detectors and the key components of the detector are gas sensors.
Gas sensors can be divided into three categories in principle:
A) Gas sensors utilizing physical and chemical properties, such as semiconductor type (surface controlled, volume controlled, surface potential type), catalytic combustion type, solid thermal conductivity type, etc.
B) Gas sensors that utilize physical properties, such as thermal conductivity, optical interference, infrared absorption, etc.
C) Gas sensors utilizing electrochemical properties, such as constant potential electrolysis, Gavanni battery, membrane ion electrode, fixed electrolyte, etc.
According to the hazards, we classify toxic and harmful gases into two categories: combustible gases and toxic gases.
Due to their different properties and hazards, their detection methods also vary.
Combustible gases are the most hazardous gases encountered in industrial settings such as petrochemicals, mainly organic gases such as alkanes and certain inorganic gases such as carbon monoxide. The explosion of combustible gases must meet certain conditions, namely: a certain concentration of combustible gases, a certain amount of oxygen, and sufficient heat to ignite their ignition source. These are the three elements of explosion (as shown in the explosion triangle in the left figure above), all of which are indispensable. In other words, the absence of any of these conditions will not cause fire and explosion. When combustible gases (steam, dust) and oxygen are mixed and reach a certain concentration, an explosion will occur when encountering a fire source with a certain temperature. We refer to the concentration of combustible gases that can explode when they come into contact with a fire source as the explosion concentration limit, abbreviated as the explosion limit, which is generally expressed in%. In fact, this mixture does not necessarily explode in any mixing ratio and requires a concentration range.
