Fire doors may be made of a combination of materials, such as:
- gypsum (as an endothermic fill)
- glass sections
Door hardware includes, but is not limited to:
- Automatic closing devices.
- Ball bearing hinges.
- Positive latching mechanism.
Edges of a fire door usually need to have fire rated seals which can be composed of:
An intumescent strip, which expands when exposed to heat
- Neoprene weatherstripping
- Gaskets to prevent the passage of smoke
Some fire doors are equipped with internal windows which also have a rating, or have been incorporated at the time of the door test and be subject to the overall door's product certification. Fire-resistive windows must remain intact under fire conditions and hose stream impact resistance, and can include:
- Wire mesh glass
- Liquid sodium silicate fills between two window panes
- Ceramic glasses
- Borosilicate glass
Wired glass typically withstands the fire, whereas the sodium silicate liquid also acts to insulate heat transfer, due to the endothermic action of this chemical.
All components are required to adhere to product certification requirements that are acceptable to the local Authority Having Jurisdiction (AHJ) by meeting the requirements of the local building code and fire code. The regulatory requirement will change from country to country.
For example in the United Kingdom a fire resisting doorset should be subjected to either a British Standard Fire Test BS 476 Part 22 1987, or a BS/EN 1634-1 2000 test. The results are recorded by the test agency and provided in a report which detail such things as constructional details, distortion data and pressure readings. The numerical fire resistance rating that is required to be installed in a particular building is provided in the Building Regulations approved Document B, or British Standards such as the BS 5588 series (e.g., 30 minutes FD30, or FD30(S) if cold smoke resistance is also required).
Similar technical guidance documents and building regulations are in effect in other countries.
Fire doors are not necessarily noncombustible. It is acceptable for portions of the door to be destroyed by combustion during exposure to a fire as long as the door assembly meets the fire test criteria of limiting temperature limits on the non-fire side of the assembly. This is in accordance with the overall performance goal of a fire rated door to slow fire propagation from one fire rated compartment to another for only a limited amount of time, during which automatic or manual fire fighting may be employed to limit fire spread, or occupants can exit the building.
Fire doors are sometimes rendered unable to provide its listed fire resistance by ignorance of the intended use and associated restrictions and requirements, or by inappropriate use. For example, fire doors are sometimes blocked open, or carpets are run through them, which would allow the fire to travel past the fire barrier in which the door is placed. The door's certification markings are displayed both on the door leaves and the fire door frames, and should not be removed or painted over during the life of the building.
Sometimes fire doors have apparently very large gaps at the foot of them, an inch or two even, allowing air movement, such as in dormitory facilities. This can lead the occupants of a building to question their status as 'real' fire doors. Testing of fire doors include a maximum door undercut of 3/4 inch. Corridors have a fire rating of one hour or less, and the fire doors in them are required by code to have a fire rating of 1/2 or 1/3 hr, the intent of which is mainly to restrict smoke travel.
Most fire doors are designed to be kept closed at all times. Some doors are designed to stay open under normal circumstances, and close automatically in the event of a fire. Whichever method is used, the door's movement should never be impaired by a doorstop or other obstacle. The intumescent and smoke-seal bounding of fire doors should be routinely checked, as should the action of the door closer and latch.
Fire door held open by magnet
Some fire doors are held open with an electromagnet, which may be wired to a fire alarm system. If the power fails or the fire alarm is activated, the coil is de-energized and the door closes on its own.
Rated fire doors are tested to withstand a fire for a specified period. There are 20, 30, 45, 60 and 90-minute-rated fire doors that are certified by an approved laboratory (e.g. Underwriters Laboratories). The certification only applies if all parts of the installation are correctly specified and installed. For example, fitting the wrong kind of glazing may severely reduce the door's fire resistance period.
As well as ensuring the door is hung properly and squarely, it is also very important that where a fire door is installed, any gaps left in the opening between the wall and the door frame must be properly filled with fire resisting material. Fire doors are normally installed by a carpenter.