Problems Existing in the Selection of Toxic and Hazardous Gas Detectors at Present
① More emphasis is placed on the detection of flammable gases than toxic gases.
② Greater attention is paid to gases that may cause acute poisoning than those leading to chronic poisoning.
Bloody lessons from explosion accidents caused by numerous flammable gas leaks have made people attach great importance to flammable gas detection. Practically in every petrochemical and chemical plant, the vast majority of hazardous gas detectors are LEL detectors. However, being equipped only with LEL detectors is far from sufficient to fully safeguard workers' safety and health. Admittedly, most volatile hazardous gases are flammable, yet catalytic combustion flammable gas (LEL) detectors are not the optimal solution for all flammable gas measurements. They are specially calibrated for methane and deliver poor detection performance for other substances. Consequently, the minimum detectable concentrations of flammable gases other than methane on these devices are far higher than their permissible exposure limits.
For example, it is extremely dangerous to rely solely on flammable gas detectors for toxic hazardous gases such as benzene and ammonia. The lower explosive limit (LEL) of benzene is 1.2%, with a correction factor of 2.51 on LEL instruments. This means an LEL detector calibrated with methane only displays 40% of benzene's actual concentration. The lowest alarm threshold for benzene on an LEL detector is 10% LEL = 10% × 1.2% × 2.51 = 3.0×10⁻³, which is nearly 600 times higher than benzene's permissible exposure limit of 5×10⁻⁶. Similarly, the alarm concentration of ammonia measured by an LEL detector is 1.5×10⁻², roughly 600 times its allowable limit of 2.5×10⁻⁵. Therefore, selecting dedicated toxic gas detectors according to the target measured gases is far safer and more reliable than simply deploying LEL detectors.
Furthermore, current practices focus heavily on gases that trigger acute poisoning, such as hydrogen sulfide and hydrocyanic acid, while insufficient attention is given to substances causing chronic poisoning, including aromatic hydrocarbons and alcohols. In fact, the latter pose no less threat to workers' safety and health than acute-toxic gases. They may induce cancer and other latent illnesses, impairing employees' long-term health and lifespan. Apart from insufficient awareness, a key contributing factor was the previous lack of suitable instruments on the market capable of detecting low-concentration organic vapors. With advances in technology and rising public awareness of occupational health, people no longer merely aim for safe commuting to and from work, but pursue superior overall quality of life. They care not only about their current working conditions but also about their long-term well-being after retirement.
