Information problems existing in the selection of harmful gas detectors
When oxygen is used in industrial environments, especially in enclosed environments, there are factors that require great attention. Generally, we consider an oxygen content exceeding 23.5% as excessive oxygen (oxygen enrichment), and in this case, there is a high risk of explosion; while an oxygen content lower than 19.5% is regarded as insufficient oxygen (oxygen deficiency), and at this time, workers are highly prone to the risks of asphyxiation, coma, and even death. The normal oxygen content should be around 20.9%. The oxygen detector is also a type of electrochemical sensor.
Currently, the problems existing in the selection of harmful gas detectors:
In China, due to historical and cognitive reasons, there are still quite a few problems when selecting various types of detectors, which are specifically reflected in the following aspects:
More emphasis is placed on the detection of combustible gases than on the detection of toxic gases.
More emphasis is placed on the detection of gases that may cause acute poisoning than on the detection of gases that may cause chronic poisoning.
Due to the bitter lessons learned from numerous explosion accidents caused by the leakage of combustible gases, people attach great importance to the detection of combustible gases. It can be said that in any petrochemical or chemical plant, the vast majority of hazardous gas detectors are LEL detectors. However, merely equipped with LEL detectors is far from sufficient to truly protect the safety and health of workers.
It is undeniable that most volatile hazardous gases are combustible gases. However, the catalytic combustion type of combustible gas detector (LEL) is not the best choice for detecting all combustible gases. It is specifically designed for the detection of methane, and its detection performance for other substances is relatively poor. Therefore, the lower limit concentrations of combustible gases other than methane that they can detect are much higher than their allowable concentrations. For example, for hazardous and toxic gases such as benzene and ammonia, simply using a combustible gas detector is a very dangerous practice. For instance, the lower explosive limit of benzene is 1.2%, and its correction factor on the LEL detector is 2.51. That is to say, the concentration of benzene displayed on an LEL detector calibrated with methane is only 40% of its actual concentration!! In this way, the lowest alarm concentration of benzene that can be detected by the LEL detector is 10% LEL = 10% * 1.2% * 2.51 = 3.0 * 10⁻³, and this concentration is nearly 600 times higher than the allowable concentration of benzene, which is 5 * 10⁻⁶!! Similarly, the alarm concentration of ammonia obtained on the LEL detector, which is 1.5 * 10⁻², is also approximately 600 times higher than its allowable concentration of 2.5 * 10⁻⁵. Therefore, depending on the gas being detected, choosing a specific toxic gas detector is much safer and more reliable than simply choosing an LEL detector.
