The main object of tunnel ventilation is to remove harmful and unwanted contaminants from the air so that people and equipment can use the tunnel safely. A tunnel is a long, enclosed space where air does not renew itself. Without a planned ventilation system, exhaust gases from vehicles and trains, dust from brakes or mining operations, and heat from equipment would accumulate quickly. Tunnel ventilation, driven by axial and centrifugal fans, is designed specifically to remove these pollutants and replace them with cleaner air.
First, tunnel ventilation aims to remove exhaust gases. Road tunnels carry vehicles that emit carbon monoxide, nitrogen oxides and unburned hydrocarbons, while rail and metro tunnels may have diesel locomotives or rolling stock that generate similar pollutants. In mining or industrial tunnels, diesel equipment, blasting and process machinery add further gases and vapors. Ventilation systems extract these exhaust gases and dilute them with fresh air so that concentrations stay within legal and health limits.
Another key object is to remove smoke and toxic products during a fire. A fire in a tunnel can generate thick smoke, carbon monoxide and other toxic gases in a very short time. The tunnel ventilation system must be able to switch to emergency modes in which exhaust fans, jet fans and dampers work together to extract smoke in a controlled direction. The objective is to clear escape routes, protect refuge areas and create acceptable conditions for fire and rescue teams.
Tunnel ventilation is also used to remove dust and fine particulates. Brake dust, tire particles, ballast dust, and in mining tunnels rock dust and blasting fumes can all reduce visibility and cause long-term health issues. Continuous airflow carries these particles toward exhaust shafts or filtration units, reducing their concentration in the breathing zone and helping to keep tunnel surfaces cleaner.
Finally, an important object of tunnel ventilation is to remove excess heat and humidity. Engines, braking systems, transformers, cables and lighting all produce heat. In long or deep tunnels the surrounding rock may be warm and groundwater may add moisture. Ventilation removes hot, humid air and brings in cooler, drier air, preventing overheating of equipment, fogging and condensation on walls, lights and signs.
In summary, the object of tunnel ventilation is to remove exhaust gases, smoke, dust, heat and unwanted fumes so that the tunnel remains safe, breathable and operational under both normal traffic and emergency conditions.
