Application of Gas Detector in Tunnel
The toxic and harmful gases in the tunnel are very dangerous, and if the construction is not done properly, major safety accidents will easily occur. Harmful gases in the tunnel mainly include methane, carbon monoxide, carbon dioxide, hydrogen sulfide, nitrogen and varying amounts of heavy hydrocarbons and trace amounts of rare gases.
The main components of the flammable gas in the tunnel are methane (CH4, gas) and some volatile organic compounds (VOC). The main hazard is the explosion caused by gas combustion. However, certain conditions must be met for the explosion of combustible gas, such as a certain amount of combustible gas, enough oxygen and an ignition source. The above three conditions are indispensable. The gas concentration at which a flammable gas explodes is usually called the lowest explosion limit, generally expressed in LEL. Different combustible gases have different LELs. Therefore, for the detection of combustible gases, its LEL is generally detected.
The toxic gases in the tunnel are divided into three categories according to their different mechanisms of action on the human body: irritating gases, asphyxiating gases and acute poisoning organic gases (VOC).
The first category: irritating gases include [chlorine, phosgene, diphosgene, sulfur dioxide, nitrogen oxides, formaldehyde, ammonia, ozone] and other gases. The characteristic of the action of irritating gas on the body is that it has a strong stimulating effect on the skin and mucous membranes, and some of them have a strong corrosive effect at the same time.
The second category: Asphyxiating gases include [carbon monoxide, hydrogen sulfide, hydrogen cyanide, carbon dioxide, nitrogen, methane, ethane, ethylene, vapor of nitrobenzene, hydrogen cyanide] and other gases. These compounds lead to hypoxia of tissue cells after entering the body. It is worth mentioning that methane (CH4) can also be an asphyxiating gas. It itself has no obvious toxicity to the body. The hypoxia of tissue cells caused by it is actually hypoxic asphyxia caused by the decrease in the oxygen concentration in the inhaled air. Acute poisoning organic solvents include n-hexane, dichloromethane, etc.
The third category: three categories of acute poisoning organic gases (VOC). The above-mentioned organic volatile compounds, like the above-mentioned inorganic toxic gases, will also cause harm to the human respiratory system and nervous system, and some are carcinogenic, such as benzene. Since organic compounds are mostly flammable substances, most of the detection of organic compounds used to detect its explosiveness, but the lowest explosion limit of organic compounds is far greater than its MAC (Maximum Allowable Concentration in Space) value. In other words, it is necessary and necessary to detect the toxicity of organic compounds. Such as n-hexane, dichloromethane, etc. However, it is usually the value when the lower explosive limit (LEL) concentration of the gas is not reached. Its toxicity has already caused harm to the human body, so for the detection of organic compounds (VOC), we must first test the toxicity, and then test the explosion.
For the safety of tunnel construction, we need to monitor the concentration of toxic gases in the tunnel in real time. Portable four-in-one gas detectors are often used in tunnels to detect flammable gases, carbon monoxide, hydrogen sulfide and oxygen at the same time, real-time detection, sound, light and vibration alarm, so as to ensure the safety of staff.
