Information problems in choosing a hazardous gas detector
Oxygen in the use of industrial environments, especially in confined environments need to pay close attention to the factors. Generally we will be more than 23.5 per cent of the oxygen content is called oxygen excess (oxygen-rich), at this time it is easy to occur the risk of explosion; while the oxygen content is less than 19.5 per cent of the oxygen for the oxygen shortage (oxygen deficiency), at this time it is easy to occur the risk of workers asphyxiation, coma and even death. Normal oxygen content should be about 20.9%. Oxygen detector is also a kind of electrochemical sensor.
Current problems in selecting harmful gas detectors:
In our country, due to historical and cognitive reasons, we still have more problems in the selection of various types of detectors, specifically reflected in:
1)The detection of combustible gases is heavier than the detection of toxic gases.
2) the detection of gases that may cause acute poisoning is heavier than the detection of gases that may cause chronic poisoning.
Due to the many combustible gas leakage caused by the explosion of the blood lessons, so that people for the combustible gas detection attaches great importance to any petrochemical, chemical plants, the vast majority of dangerous gas detector are LEL detector. But only equipped with LEL detectors for the real protection of workers' safety and health is still far from enough.
It is undeniable that most volatile hazardous gases are flammable gases, but the catalytic combustion type of flammable gas detector (LEL) is not the best choice for all flammable gas detection. It is specifically designed to detect methane and has poorer detection performance for other substances. 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 dangerous toxic gases such as benzene and ammonia, simply using a combustible gas detector is a very dangerous practice. For example, benzene has a lower explosive limit of 1.2% and its correction factor on a LEL detector is 2.51, i.e. benzene's concentration on a LEL detector calibrated with methane is only 40% of its actual concentration!!!! Thus, the *lowest* alarm concentration of benzene that can be detected by LEL is 10% LEL = 10% * 1.2% * 2.51 = 3.0*10-3, which is nearly 600 times higher than the permissible benzene concentration of 5*10-6!!!! Similarly, ammonia gives an alarm concentration of 1.5*10-2 on the LEL detector, which is about 600 times higher than its permissible 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 choosing a LEL detector alone.
