Tunnel Fire Ventilation

Ventilation is the most common measure to mitigate the effect of fire and smoke in a tunnel. Various normal ventilation systems for removal of heat and contaminants from the tunnels are introduced at first. In case of a tunnel fire, fire ventilation systems are required to control smoke flows and create paths for evacuation and fire-fighting. The fire ventilation systems used in tunnels mainly include longitudinal ventilation systems and smoke extraction ventilation systems, which are discussed in great detail in this chapter. Two key parameters for tunnels with longitudinal ventilation, i.e. critical velocity and backlayering length, are investigated in full detail. For smoke extraction systems, sufficient fresh air flows are required to be supplied from both sides to prevent further smoke spread. Further, fire ventilation systems in tunnel cross-passages and rescue stations are discussed. A simple model of longitudinal flows is introduced for calculation of longitudinal ventilation velocity in a tunnel fire.