Fire Safety Science Digital Archive

With the object of estimating the hazard from the smoke logging of a pedestrian mall measurements of the rate of travel of smoke and the depth of the smoke layer have been made in a disused railway tunnel 600 m (2000 ft) long. The ends were open or closed and three sizes of fire were used. The smoke layer, at first dense and well stratified, travelled at a speed in the order of 1 m/s (3 ft/s). Both the speed of travel of the smoke and the thickness of the layer (which both increase with the size of the fire) agree with a theory recently developed. Thinner smoke was formed under the dense layer, sometimes causing smokelogging to the floor, particularly at the ends of the tunnel, the closed end situation being particularly bad.