For flats with floors over 4.5m, fire doors close off risk areas such as kitchens and living rooms from exit routes such as entrance halls. Individual flat entrances may also need fire doors to protect communal corridors that could, in themselves, require subdivision by fire doors to reduce travel distances to safety. For non-dwellings, there are various requirements for fire doors to protect and sub-divide escape routes. The ease of operation, swing direction and need for vision panels in fire doors are also stipulated.

Section B3 deals with the protection of structure (to allow escape to occur), the separation of different buildings and the compartmentation or sub-division of space within a single building to limit the rapid spread of fire. Openings in any of these fire separating elements must be protected and fire doors used within them to match the element’s fire rating.

Section B5 deals with access and facilities for the fire service, in particular fire-fighting shafts, comprising of lifts, stairs and lobbies - all protected by fire doors.

Section B2, which deals with the surface spread of flame characteristics of internal walls and ceilings, specifically excludes doors from its requirements.