Toxic Gas Dispersion and Risk Assessment Considering Crowd Movement Conditions

ABSTRACT Massive releases of toxic gases usually lead to large‐scale evacuations, and the traffic force generated by crowd movements can affect the diffusion and spread of gases. Previous risk assessment methods focused mainly on the variation in gas concentration with time at different fixed locations and did not consider the coupled effect of obstacle motion and gas dispersion. This work combines gas dispersion modeling with crowd motion and introduces a respiratory frequency factor to improve personnel risk assessment methods in the presence of toxic gas dispersion by considering changes in the respiratory rate due to movement speed. The approach is applied to a hypothetical scenario where an accidental chlorine gas leak in a chemical factory has triggered the evacuation of people toward the exits. The temporal and spatial distribution characteristics of the toxic gas concentration during the movement of the crowd after the dispersion of the toxic gas were investigated to predict the hazardous consequences in each part of the crowd.