ABSTRACT Tunnel fires are one of the most dangerous risks in contemporary transportation infrastructure, where the geometry of the tunnel is limited by the existing natural ventilation, and smoke and toxic fumes accumulate. Although temperature and visibility have been the main concerns of numerous safety researchers, little has been done on the toxicology of the threat of combustion byproducts. Specifically, carbon monoxide (CO) and hydrogen cyanide (HCN) are major toxicants contributing to occupant harm in vehicle fires, and their combined impact on occupant survival in tunnels has received limited systematic attention. This study employs Computational Fluid Dynamics (CFD) to evaluate the distribution of CO and HCN at different rates of fire and ventilation plans. The CFD model was validated against carbon monoxide data from the benchmark Memorial Tunnel Fire Ventilation Test Program, with a maximum pointwise deviation below 12% for the selected validation case. Fire scenarios were studied on 3 fire types of passenger cars (5 MW), bus (20 MW), and heavy goods vehicle (50 MW) fires, and with ventilation of longitudinal, transverse, hybrid, and no ventilation. Results indicate that in the absence of ventilation, CO and HCN concentrations reached levels as high as 1800 and 240 ppm, respectively, leading to occupant incapacitation within 5 min. Longitudinal ventilation reduced CO and HCN concentrations by 33% and 29%, respectively, and increased SET to approximately 7 min, whereas transverse and hybrid ventilation extended SET to approximately 10.5 and 14.5 min.
Zhang et al. (Thu,) studied this question.
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