Ventilation of tunnels as a method for providing fresh air and exhausting gases from combustion in cars is very common. Even in metro tunnels where there are no combustion gases, the ventilation system is necessary in order to provide fresh air and also smoke evacuation in emergency conditions. There are different regulations for tunnel ventilation in different regions of the world. Different types of ventilation systems are also used regularly, but in the end, they all use two main types of fans, namely axial fans and jet fans. The basis of all the designs is the supply of fresh air from one part of the tunnel and its discharge from another part.
Jet fans in longitudinal systems by moving air from the air supply side to the discharge point cause the movement and discharge of pollution or smoke from the tunnel. In order to increase efficiency in the tunnel ventilation design, the amount of pollutants produced by cars or metro inside the tunnel should be calculated first. Then, having information such as the length of the tunnel and its conditions, he proceeded to choose the appropriate ventilation method.
These methods are: