Fire Safety Science Digital Archive

A study has been made of the action of sprinkler sprays on hot buoyant smoke layers, with particular reference to covered shopping complexes, to quantify the possible danger of bringing smoke down to a low level and thus impeding or preventing the escape of occupants. A theory has been developed for the interaction of the spray and buoyant gases. Graphs derived from the theory are presented which enable the conditions under which smoke-logging by the spray is likely to occur to be obtained. The experimental data available at present support this theory. Where the smoke layer is deep (~1 m) it can be shown that a layer which is hot enough to set off sprinkler heads will have sufficient buoyancy to withstand the downward drag of the sprinkler spray. Downflow may only occur later in the course of the fire when the layer is cooler, by which time the occupants should have escaped. The effect of sprinklers on thin smoke layers is discussed.