A fire door is a type of door, or barrier used as a passive fire protection item within buildings to prevent the spread of fire or smoke which may consist of dangerous chemicals. It is usually the only means of allowing people to pass through a fire-resistance rated wall assembly.
Fire doors are made of a combination of materials, such as:
* gypsum (as an endothermic fill)
Apart from the door leaf (the swinging panel of the door) there is the door frame which also has to meet fire rated regulations, intumescent strips, smoke seals, door hardware and the structure that holds the fire door assembly in place. Together, these components form an assembly, typically called a “doorset” which holds an hourly rating.
All of the components of the fire door assembly must bear a listing agencies label to ensure the components have been tested to meet the fire rating requirements.
Door hardware includes, but is not limited to:
manual or automatic closing devices
* door sweeps
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
* Smoke gasketing to prevent the passage of smoke
Intumescent seals are crucial in the fire performance of a fire resisting door set and as such the correct seal should always be used as these products differ in chemical composition, expansion rate, expansion volume and charring characteristics.
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.
Fire doors are not necessarily all noncombustible. A fire door is but one of many passive fire protection components used to compartmentalise fire and thus keep it in the compartment of origin, so either it runs out of fuel or it is extinguished, or, at the very least, enough time has been bought to enable evacuation of the building.
Fire door failure
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. Such neglect is the responsibility of the building owner, who should educate occupants on the safe use of all safety related items, to ensure fire safety and compliance with the fire code.
Sometimes fire doors have apparently very large gaps at the foot of them, an inch or two even, allowing air movement, especially 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 should be kept closed at all times, however some are designed to stay open under normal circumstances, only to shut automatically or manually in the event of a fire. Whichever method is used, the door’s movement should never be impaired by a doorstop or other obstacle. Proper intumescent and smoke-seal bounding of fire doors should be routinely checked and ensured, as should the action of the door closer and latch.
Some fire doors are held open with an electromagnetic coil, which may be wired to a fire alarm system via relays. If the power fails or the fire alarm is activated, the power to the coil is cut 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.
Construction and Installation issues
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.
In building design drawings with poor identification of which walls do in fact have a fire-resistance rating, it is often necessary to check the door schedule in the specifications to be able to trace what walls are rated and how long they are rated for. This is an indicative sign about the architect and the degree of care taken particularly with items relating to passive fire protection. To avoid confusion about any fire protection measures including fire doors, it is best for the architect to provide a separate set of drawings that clearly outlines which walls and floor have a fire-resistance rating and exactly what that rating is. It is also important to point out especially which walls are firewalls and which walls and/or floors are designated as occupancy separations, as the nature of passive fire protection devices that must be used in those special cases can be substantially different from such devices that are used in ordinary fire separations.