More and more urban traffic tunnels are built to mitigate the traffic problems in many large cities in China at present time.Fire safety problems are more important due to the large daily traffic flow

special locations and building structures in these kinds of tunnels.To understand the fire environment is a key point for the fire prevention system design.Numerical studies on the fire environment in tunnels with or without slope were carried out by software FDS in this paper.Longitudinal temperature distributions were obtained.Different fire behaviors were found for the fires occurring in the tunnels with and without slope. The results show that due to the stack effect

the temperature fields in a slope tunnel are not symmetry

hot smoke spreads towards the top exit

and the spread speed is much faster than that in the normal tunnel. This might be dangerous for the passenger’s evacuation.Special measures should be taken for these kinds of fire conditions.