Buildings are compartmentalised to delay the spread of fire from one area to another. The compartments are usually linked by doors to allow for passage of traffic around the building. Door sets have two important functions in a fire, when closed they form a barrier to fire spread and when open they provide a means of escape.
A well designed timber fire door will delay the spread of fire and smoke without causing too much hindrance to the movement of people and goods. Different parts of a building may be separated from each other, into compartments of a fire-resisting construction. Any openings leading from them will have fire doors to maintain an effective fire barrier and should prevent excessive transmission of products of combustion which can interfere with the safe use of escape routes.
Every fire door is therefore required to act as a barrier to the passage of smoke and/or fire to varying degrees dependent upon its location in a building and the fire hazard associated with the building.
- A fire door is to provide resistance to the passage of a well developed fire and consequently requires intumescent strips to be installed.
- Secondly to prevent excessive quantities of cold smoke to pass in the early stages of a fire and then to provide a barrier to a well-developed fire. They need to be fitted with intumescent strips and cold smoke seals to achieve this aim.
Some fire doors may be required to fulfil only the first function as they may not be required to prevent the passage of smoke because of their location. Others as indicated by the second function may have to resist the the passage of smoke and the spread of fire. Fire doors are specified as FD when required to fulfil the first function and FDs doors to fulfil the second.