In order to provide a safe working environment in tunnel constructions, protection against fire and explosion, prevention of accidents, prevention of health problems and occupational diseases caused by dangerous substances for workers are an inevitable necessity. Also important for tunnel constructions is that necessary precautions are taken before some risks are realized.
In tunnel constructions, gas leaks that occur suddenly or life-threatening gases accumulating over time are among the biggest risks. In order to obtain accurate results from continuous measurements, it will be necessary to know which toxic or flammable gases may emerge. In tunnel constructions, some gases are usually encountered between soil layers. These gas mixtures generally contain methane at about 90-95 by volume, carbon dioxide or hydrogen sulfide at around 2-4 by volume.
As in the construction of tunnels, harmful chemicals such as carbon monoxide, carbon dioxide, sulfur dioxide, formaldehyde and nitrogen oxide are released during use. In the main tunnels, the oxygen concentration should also be continuously controlled. Oxygen deficiency causes drowning and the risk of fire increases. Especially, the most encountered and most risky gas in the construction of tunnels is methane (CH4): Methane is odorless, colorless and lighter than air. Moreover, it is highly flammable and causes explosion when mixed with air.
Carbon monoxide (CO) is a toxic, odorless, colorless and flammable gas. If carbon monoxide is inhaled, it replaces the oxygen in the blood. This causes the cells to die. Carbon dioxide (CO2) gas is odorless, colorless and heavier than air. If inhaled for long periods of time, this gas may cause deaths. Hydrogen sulfide (H2S) is a toxic, foul-smelling, colorless, heavier than air and flammable gas. Exposure to high concentrations can suppress employees' sense of smell and may cause sudden death.
