Fire Safety Science Digital Archive

This note considers ways in which the spread of hot gases and smoke from a fire in an enclosed shopping centre may be limited. If the shop fronts are fire resisting the hot smoky gases may be confined to the shops of origin. Otherwise the size of the fire and hence the rate of 'production' of hot smoky gases must be limited (preferably by sprinklers) and it is then possible to confine the hot smoky gases to a stratified layer beneath the ceiling while the air beneath them is relatively cool and clear. The extent of the layer should be limited by dividing the space beneath the ceiling into smoke reservoirs by screens extending part of the way towards the floor. Screens by themselves are ineffective; hot gases must be extracted from a smoke reservoir at at least the same rate as they flow into it while fresh air must be introduced or allowed to flow into the building to replace the extracted hot gases. Theoretically the principle can be used to confine hot smoky gases to the space beneath the ceiling of the shop of origin but the rates of extract required can seldom be achieved on practice in the confines of a small shop and it is generally necessary to allow the smoky gases to flow into smoke reservoirs beneath the ceiling of the mall. The requirements of both natural and powered systems for extracting smoke from the smoke reservoirs are considered. It is essential that smoke control measures should be considered at any early stage in the design of the building as they may be difficult to incorporate as a later modification.