The use of gas detectors in the industry
In reality, many gases encountered in safety and health aspects are mixtures of organic and inorganic gases. However, due to various reasons, our current understanding of toxic and harmful gases is still more focused on flammable gases, gases that can cause acute poisoning (hydrogen sulfide, hydrocyanic acid, etc.), and some common toxic gases (carbon monoxide), Oxygen and other detectors, therefore, this article will first focus on introducing this type of detector, and make suggestions on the application of various toxic and harmful (inorganic/organic) gas detectors based on the current situation.
Classification of toxic and harmful gas detectors and the key component of gas detectors is the gas sensor.
Gas sensors can be divided into three major categories in principle:
A) Gas sensors that utilize physical and chemical properties: such as semiconductor type (surface control type, volume control type, surface potential type), catalytic combustion type, solid thermal conductivity type, etc.
B) Gas sensors that utilize physical properties: such as thermal conduction type, optical interference type, infrared absorption type, etc.
C) Gas sensors that utilize electrochemical properties: such as constant potential electrolytic type, Galvanic cell type, diaphragm ion electrode type, fixed electrolyte type, etc.
According to the hazard, we divide toxic and harmful gases into two categories: flammable gases and toxic gases.
Due to their different properties and hazards, their detection methods are also different.
Combustible gases are the most dangerous gases encountered in petrochemical and other industrial settings. They are mainly organic gases such as alkanes and some inorganic gases such as carbon monoxide. Certain conditions must be met for combustible gases to explode, that is: a certain concentration of combustible gases, a certain amount of oxygen and a source of fire with enough heat to ignite them. These are the three elements of explosion (as shown in the explosion triangle in the picture above on the left). One of them is missing. No, that is to say, the lack of any one of these conditions will not cause fire and explosion. When combustible gas (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 call the concentration of flammable gas that explodes when encountering a fire source called the explosion concentration limit, or explosion limit for short, generally expressed in %. In fact, this mixture will not explode at any mixing ratio but has a concentration range.
