A tunnel ventilation system located in an upper section of a tunnel has a ventilation section divided into two or three ventilation ducts. One or more of the ducts are connected to reversible fan units so the ducts can serve as either an air infeed or an air exhaust system. The ducts contain a series of remotely controlled flaps which can be opened to ventilate different tunnel zones or closed to isolate other parts of the tunnel. Air blowers at tunnel entrances create an air screen that prevents unintended air circulation into the tunnel. Heat, smoke and other sensors and a software control system enable the system to detect smoke and fire, then to isolate and control ventilation in the fire zone. A fire suppression system using low oxygen air or other fire suppression fluids to blanket and smother the fire operates in conjunction with the ventilation system.