The occupants of a building must be provided with clearly defined and safe escape routes in the event of a fire. These routes must be kept clear of obstruction, be easy to manoeuvre and, very importantly, should be free of the effects of flames, heat and smoke . For this reason escape routes need special consideration regarding safety from fire; access points must be shielded by lobbies and fire-resisting (and smoke-resisting) doors; walls and floors should have sufficient fire resistance to allow escape and subsequent access for fire-fighters to tackle the fire. Sometimes it may be necessary to provide positive air pressure in the escape route to ensure smoke is forced back into the body of the building, making exit easier, or an extractor ventilation unit can be provided to remove smoke. Internal surface finishes must not contribute to the fire or provide hazard to people escaping, and escape areas must be adequately lit, sometimes by emergency lights powered from a separate generator.
Tragedies can occur unless means of escape from a building are correctly designed and sited. In the event of a fire it should be possible to evacuate a building in reasonable time (21/2 minutes is considered normal for everyone to reach a place of safety, except for special premises such
as hospitals). Specific fire safety requirements for hospitals are contained in Health Technical Memorandum (HTM) No. 81: Fire precautions in new hospitals (Firecode). This document satisfies the objectives set out in the Building Regulations, Approved Document B. The width, the size of treads and risers, and heights of handrails for staircases used for escape purposes must also conform to similar safety requirements. Escape-route planning should therefore be related to the use of the building, the number of occupants, the risks involved, and to the heights of floors above ground and the shapes and dimensions of floors. The risk of persons being trapped or overcome by the
effects of a fire is greatest in multi-storey buildings, and access routes and standing positions for fire-brigade appliances are critical factors in the design of escape routes.
For an appreciation of the minimum dimensions and location of escape routes in a variety of building types, refer to BS 5588: Fire precautions in design, construction and use of buildings.