Noxious gas detector selection information problems
The use of oxygen in industrial environments, especially in enclosed environments, requires great attention to factors. Generally, if the oxygen content exceeds 23.5%, it is called oxygen excess (enriched oxygen), which can easily lead to the risk of explosion; If the oxygen content is less than 19.5%, it indicates insufficient oxygen (hypoxia), which can easily lead to the risk of worker suffocation, coma, and even death. The normal oxygen content should be around 20.9%. Oxygen detectors are also a type of electrochemical sensor.
In China, due to historical and cognitive reasons, there are still many problems that exist when selecting various types of detectors, which are specifically reflected in:
1) The detection of combustible gases is more important than the detection of toxic gases.
2) The detection of gases that may cause acute poisoning is more important than the detection of gases that may cause chronic poisoning.
Due to the lessons learned from numerous explosion accidents caused by combustible gas leaks, people attach great importance to combustible gas detection. It can be said that in any petrochemical or chemical plant, the vast majority of hazardous gas detectors are LEL detectors. However, equipping only LEL detectors is still far from enough to truly protect the safety and health of workers.
It is undeniable that most volatile hazardous gases are combustible gases, but catalytic combustion combustible gas detectors (LELs) are not the best choice for all combustible gas detection. It is specifically designed for detecting methane, and its detection performance for other substances is relatively poor. So, the lower limit concentration of combustible gases other than methane that they can detect is much higher than their allowable concentration. For example, for hazardous and toxic gases such as benzene and ammonia, using a combustible gas detector alone is a very dangerous practice. For example, the lower explosive limit of benzene is 1.2%, and its correction coefficient on the LEL detector is 2.51, which means that the displayed concentration of benzene on an LEL detector calibrated with methane is only 40% of its actual concentration!! In this way, the minimum alarm concentration of benzene that can be detected with LEL is 10% LEL=10% * 1.2% * 2.51=3.0 * 10-3, which is nearly 600 times higher than the allowable concentration of benzene of 5 * 10-6!!. Similarly, the alarm concentration of 1.5 * 10-2 obtained by ammonia on the LEL detector is approximately 600 times higher than its allowable concentration of 2.5 * 10-5. Therefore, based on the different gases being detected, choosing a specific toxic gas detector is much more reliable than simply choosing an LEL detector.
