Information-related Issues in Selecting Hazardous Gas Detectors
English Translation
Great attention must be paid to oxygen levels in industrial environments, especially confined spaces. Oxygen concentration above 23.5% is defined as oxygen enrichment, which poses a high risk of explosion; oxygen concentration below 19.5% indicates oxygen deficiency, likely causing suffocation, coma and even fatal accidents among staff. The normal oxygen content is around 20.9%. Oxygen detectors adopt electrochemical sensors as their core components.
Current Problems in Selecting Hazardous Gas Detectors
Due to historical factors and insufficient professional awareness, many common problems still exist in the selection of gas detection equipment in China, mainly reflected in the following aspects:
More emphasis is placed on flammable gas detection rather than toxic gas detection.
Priority is given to detecting gases causing acute poisoning over those leading to chronic poisoning.
Painful lessons from frequent explosion accidents caused by flammable gas leaks have made flammable gas detection highly valued. In petrochemical and chemical plants, most deployed gas detectors are LEL detectors. Nevertheless, relying solely on LEL detectors is far from sufficient to fully guarantee workers' personal safety and health.
It is true that most volatile hazardous gases are flammable, yet catalytic combustion-type LEL detectors are not the optimal solution for all flammable gas detection. They are primarily designed for methane detection and deliver poor detection performance for other substances. Hence, their detectable lower limit concentrations for flammable gases other than methane are far higher than the permissible exposure limits.
For instance, taking benzene and ammonia as typical toxic hazardous gases, using only LEL detectors for monitoring is extremely dangerous. The lower explosive limit of benzene is 1.2%, with a correction factor of 2.51 for LEL detectors calibrated by methane. This means the reading shown on such an LEL detector is merely 40% of the actual benzene concentration.
The minimum alarm concentration of benzene detected by LEL detectors is far higher than its occupational permissible limit, nearly 600 times in difference. Similarly, the alarm concentration of ammonia detected by LEL detectors is also about 600 times higher than its safe exposure standard. Therefore, selecting dedicated toxic gas detectors according to actual monitored gases is far more accurate and reliable than simply adopting general LEL detectors.
