Fire Safety Science Digital Archive

Among all the tenability criteria, reduction in visibility due to smoke obscuration has been regarded as the most critical factor in fire life safety. This is especially important for smoke management in underground spaces such as rail stations. This paper presents an approach to predict visibility from CFD and quantifies smoke visibility as a line integral using a simplified ray-tracing model. The application of this model is demonstrated for a mid-platform train fire scenario in an underground rail station. Both natural ventilation and a concept of mechanical ventilation are studied, and the visibility conditions are compared at three selected locations along the egress paths. Quantitatively, the smoke layer height on the platform and the change of visibility on the mezzanine are evaluated, from which a better understanding is obtained on the effectiveness of the emergency ventilation. The egress accessibility during emergency evacuation and further developments of the smoke visibility model are discussed.