A fire resistant door is specially constructed to slow or prevent the spread of fire and smoke. These doors are not designed to be completely fireproof, and are actually made of combustible materials. Though they will eventually burn in a fire, they will resistant high levels of heat and flames to slow the fire for a specified period of time. By keeping the fire contained, fire doors may allow more occupants to safely exit the building during an emergency. They may also help to protect property and assets while firefighters work to put out the flames.
To help ensure that these doors will function as intended, fire doors are closely regulated by independent governing bodies. In the United States, these doors must be constructed, tested, and installed according to standards created by the National Fire Protection Association (NFPA). Similar standards are set by the British Woodworking Federation in the UK, and by other governing bodies throughout the world. At the local level, a fire resistant door may also be subject to inspection and approval by the authority in that jurisdiction, often the fire marshal or building inspector.
These doors are installed in fire resistant walls. The wall must first be rated according to the amount of time it is designed to prevent the spread of a fire. For example, a two-hour wall will contain flames and smoke while resisting combustion for two full hours. A door must have a fire rating equal to three-fourths of the wall rating. For example, a fire resistant door installed in a two-hour wall will have a rating of 90 minutes.
Fire doors are typically only installed within interior openings in a building. They are used in exterior walls only when the building is located very close to another structure, or close to the property line or roadway. A fire resistant door is useless unless it is installed in a fire rated opening. If the wall is not designed to resist fire, the door will quickly fail.
Doors used in fire rated walls can be constructed from wood, aluminum or steel. They will usually have a fire resistant core made from gypsum or a similar mineral-based product. All fire resistant doors must be equipped with a label or marking system indicating the rating of the door. In the US, this label may be mechanically fastened or embossed on the door. While the UK and Europe also use labels, you are more likely to find colored pins embedded into the edge of the door to indicate the fire rating.
The frame and hardware used with a fire resistant door must also be tested and labeled for use in a fire. Most modern fire door codes also require the use of intumescent seals. These seals will automatically expand when exposed to high temperatures to help seal the space around the door. The doors must also be self-closing and self-latching, and can not be held open by any mechanical door stops or other devices.