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.
Every fire door is therefore required to act as a barrier to the passage of smoke and/or fire to varying degrees depending upon its location in a building and the fire hazards associated with that building.
- A fire door required to provide resistance to the passage of a well-developed fire must be fitted with in-tumescent seals. These seals remain dormant under normal conditions but expand greatly in the heat of a fire to close the gap between the door and its frame.
As smoke spread is an even greater threat to life and property than flames, particularly in the early stages of a fire, fire doors should also be fitted with a ‘cold smoke’ seal to prevent the ingress of smoke around the door edges. Combined smoke and in-tumescent seals protect from all aspects of fire in a single unit
Some fire doors only require in-tumescent seals (specified as FD fire doors). Others may have to resist the passage of smoke as well as the spread of fire (specified as FDs fire doors).