Fire Barriers : When a fire starts in a building it spreads quickly by:
a) Radiation - Intense heat radiates to neighbouring surfaces which are rapidly heated to ignition point. Materials themselves then ignite or when heated give off flammable gases and vapours.
b) Convection - Flames and hot gases rise by convection increasing the effects of radiation and burning the surfaces they touch. Thus ceilings quickly ignite and staircases and lift shafts often become quickest ways of spreading a fire.
The spread of fire can be limited by compartmentalization the interior of a building with fire barriers such as
1. fire doors
2. fire retardant walls
3. fire resistant floors
Fire doors are fitted with self -closing hinges and are always hung so as to open outwards towards the fire exit. They act in two additional ways in fire prevention
i) they restrict oxygen supply to the fire.
ii) they act as smoke barriers.
Fire doors should always be kept closed and should never be obstructed.