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INTRDUCTION

Smoke detectors are widely used in commercial premises to detect the smoke from a fire in its initial stages. By providing reliable early warning, they offer property protection as well as alerting building occupants and allowing them time to escape. In high ceiling spaces the smoke movement is influenced by many factors such as air movement, stratification and the smoke concentration, which depends on the fire size and the volume of the room. With so many variables, it is complicated to specify the type and location of the smoke detector and to be confident of its detection capabilities.

The performance of aspirating and optical beam smoke detectors has not previously been characterised for use in high ceiling spaces such as atria, warehouses and entertainment venues within buildings, where there is a demand for their application. The code of practice BS 5839-1:2002[1] permits the use of aspirating smoke detectors (aspirators or ASDs) up to a height of 21 m in areas where rapid fire and rescue service attendance is possible, and permits optical beam smoke detectors (beams) up to a height of 40 m. However, in general applications aspirators are limited to heights of 15 m and beams to heights of 25 m. The origins and scientific basis for these limits in the code of practice are not known.

In order to assess the capabilities and limitations of aspirating and optical beam smoke detectors installed in high ceiling spaces, BRE Trust and the FIA jointly funded a programme of work that incorporated computer modelling as well as a series of fire tests. The project reported here investigated the performance of both aspirators and beams in high ceiling spaces when exposed to different types of smoke. This Information Paper provides useful data and recommendations for manufacturers and installers of smoke detectors, as well as building designers and regulators, and shows that both types of detector adequately demonstrated their capability to detect smoke when installed in ceilings 43.5 m high.