Abstract: In order to optimize public evacuation process under conditions of toxic gas leakage, based on Gauss plume model of gas dispersion, a function for optimal evacuation route was established with smallest dose of inhaled toxic gas for public as the objective. Then, the function was solved by variational method with moving boundaries so as to obtain optimal evacuation route. Then analysis on inhaled dose of toxic gas by the public and range analysis under different influencing factors were conducted, and death zone due to public evacuation without protection was calculated. The results show under conditions of toxic gas leakage, directions of optimal evacuation routes are consistent with side wind of ambient wind, rather than along headwind direction. It is recommended that the public evacuate towards the direction that is perpendicular to wind direction. Those near to and at a distance from the leak source face the greatest danger during evacuation. The biggest factor that causes gas poisoning during evacuation is leakage rate, followed by atmospheric stability, and impact of average evacuation speed can be negligible, so it is not recommended to evacuate blindly without protection. The suggestion is that in areas with a high probability of death, the public should be sheltered in place, while those outside areas with a low probability of death could be evacuated.

Key words: optimal evacuation route, toxic gas leakage, leakage rate, public evacuation, death probability