Transverse distributions of CO, visibility and temperature during fire in the Xuefengshan Highway Tunnel

FDS4.0 (Fire Dynamic Simulator) was employed to study the transverse distribution of fire smoke in road tunnel, with several heat release rates (5 MW, 20 MW and 50 MW) and with longitudinal ventilation or no ventilation. The tunnel model grid was formed by using the multiple-mesh technique with small rectangular parallelepipeds. It is found that CO concentration along the centerline is smaller than in the vicinity of the side walls, and visibility is larger along the centerline than in the vicinity of the side walls, while there is no apparent difference in temperature between centerline and the side walls. The gradients of CO and visibility in the transverse direction are larger with ventilation than that under ventilation failure, and due to convection, there are relatively lower CO concentration and larger visibility near the fire. For unidirectional traffic tunnels, personnel should evacuate under guidance, and if no guidance available, people should evacuate along the centerline rather than the walkway.