The piston style can be used in one -way transportation. The cost of the project is low, the implementation of it is easy, and the operating costs are low.

2 Half -horizontal ventilation

When a fire occurs in the tunnel, the gauge can reverse and prevent the fire from spreading. The concentration of harmful gases in the lane is even uniform, only one air duct, low engineering investment. In theory, there is a neutral face at the location of the center line of the tunnel, and the traffic status in the actual situation is constantly changing. A neutral belt is formed in the middle of the tunnel. The ventilation effect of this area is worse than other places, and it is difficult to implement in installments.

3 Full horizontal ventilation

The ventilation flow flows horizontally in the tunnel, with good ventilation effect and strong safety. It can be discharged in time when fire occurs in the tunnel. However, two air ducts must be set up in the tunnel to occupy the tunnel area, high engineering cost, and high operating costs.