Emergency evacuation risk assessment and mitigation strategy for a toxic gas leak in an underground space: The case of a subway station in Guangzhou, China

Abstract

In emergency system design, evacuating people from dangerous buildings has always been a significant yet challenging undertaking. This paper combines evacuation demand analysis with a toxic gas dispersion process to create an underground space risk assessment model for toxic gas leaks. The emergency evacuation capacity of a subway transfer station in Guangzhou has been evaluated and optimized based on computational fluid dynamics (CFD) and agent-based simulation. A strategy is proposed in which the subway ventilation system in the underground space is utilized to mitigate evacuation risks during gas leaks. The influence of the ventilation system on the gas diffusion process under different working conditions during simulations of toxic gas diffusion is also analyzed. A comparative analysis is conducted to discuss whether to adopt the ventilation system. Then, the effectiveness of the risk methods when the ventilation system is utilized in different working conditions is also verified. An empirical model of the impacts of the number of evacuees and individual risk perception levels on the evacuation risk has been obtained. Results indicate that the new risk assessment and risk mitigation methods are effective and can help guide the emergency evacuation and ventilation system design for underground buildings.