Abstract: In toxic gas leakage accidents, the spread of harmful substances has a significant impact on the evacuees' route choice behavior. In view of this fact, a new model was built for planning evacuation routes. The minimum damage to evacuees was taken as the target of evacuation process planning. Discretization improvements were made on the formula of toxic load. The toxicity injury indexes for various evacuation route sections, such as the toxic load value, the probability of death, were calculated by using the Gauss gas diffusion model on the basis of the information on the position shown in the evacuation toad network graph, so as to select the optimal evacuation route. The model was applied to an assumed ammonia-leakage accident. The research results show that due to the difference in the toxic gas concentration distribution, an evacuation scheme resulting in a shorter walking distance, is likely to lead to a higher damage probability, and that in order to reduce evacuees' damage and casualty, the emergency-evacuation process needs an accurate guide based on the model.

Key words: emergency evacuation, toxic gas leaking, Gaussian diffusion model, toxic load, death probability