1. Provide fresh air to the front (to the inside).

2. Inverse (outer) and ventilation effects.

Generally, tunnel fans supply air inwards, but in special cases they must exhaust air outwards. Generally speaking, the horizontal air valve is opened in normal times, the vertical air valve is opened in a fire, and there is a special emergency fan for emergency situations.

Therefore, the tunnel fan should have the function of positive and negative reversal, so that the tunnel fan can run normally and send fresh and fresh air into the tunnel. Once a dangerous accident occurs, it will immediately reverse the state of the risky situation, and the danger can be effectively eliminated. and closing tunnel personnel. low risk.