Fire Doors

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.

Specifications of timber fire doors

The performance of timber doors is judged by subjecting them to the standard test procedure specified in BS 476 : Part 22: 1987 or BS EN 1634-1: 2000. Tests are made on complete door assemblies, the fire door and frame with all the necessary hardware. It is then fixed in a wall representing its use in practice. By testing a door in one type of frame and using it in another, no guarantee can be given of its behaviour under fire conditions. The test procedure is fully described in the Standard and consists of exposing one face of the door to heat condition expected in a fire whilst observing the door for stability and integrity. The Standard requires the tests to be carried out with the upper part of the door under a small positive pressure, to simulate the conditions likely to occur in a fire. It also provides an objective method of establishing the loss of integrity of a fire door by the use of a combustible fibrous pad on the un-exposed side of the door and see when it ignites. A fire door should be tested from each side to establish its performance with either face exposed to fire conditions, consequently requires two specimens.It is reasonable assumed all fire doors and frames manufactured to the same specification as the two specimen doors and frames will achieve the same fire resisting properties. A technique has been developed for minimising the susceptibility of door edges to early penetration by fire. It consists of applying intumescent seals to the edges so that a rise in temperature will cause the material to swell and close the gaps. Intumescent paints have been used but the most successful and reliable technique is the intumescent seal, about 4mm thick by 10 mm wide, cut into a groove in the door or the frame edge or in some cases surface mounted. As soon as the temperature in the vicinity of the strips exceeds 200°C, usually about 10-15 minutes after the start of a fire, the seal swells and seals the gaps. One fire door seal is adequate for a half hour fire door and for the increased protection needed with one-hour doors, two of these seals will be necessary. The intumescent material is soft and cellular in structure and will not prevent deformation of the door. There are fire doors that are able to resist the passage of fire for more than 30/60 minutes but these are more likely to be used for the protection of property than for means of escape from fire.

Fire resisting doors – Door type for means of escape purposes	Integrity Minutes	Stability [2] Minutes
Half-hour fire-resisting	30	30
One-hour fire-resisting	60	60

[1] Integrity Failure is deemed to occur when

cracks or other openings exist through which flames or hot gases can pass

or when flaming occurs on the unexposed face.

[2] Stability Failure is deemed to occur when

collapse of the specimen takes place.

Identifying Fire Doors

Certified Fire Doors

Manufacturers can certify fire door sets so they are easily identified and with a guarantee to behave in a fire as they should. The first step for the manufacturer is to construct a fire door set designed to a specification that in the opinion of the manufacturer will resist a fire for a specified time. This door set is then tested by an approved fire testing centre and if it passes the test any door sets constructed to that specification can be considered for certification.

Once the certification is approved all similar constructed door sets are identified by labels. This will identify the manufacturer, the date of manufacture and the design fire rating of the door type. They may fit a colour coded plug instead of or in addition to the label. Identification labels are usually fitted on the top edge of the door and plugs inserted in the jamb of the door. For Hospitals, fire doors display a disc at the top of each face of the door showing the design fire performance see HTM58.

Identification marks can sometimes be removed during installation or adjustment of the assembly or may have been painted over but if the door set has been installed by a competent joiner this should not happen. There are two associations that have certifiable fire door systems. they are:-

TRADA Q-Mark fire door scheme

The woodworking association BM TRADA use a system called Q-Mark it uses coloured plugs inserted in the jamb of the door which indicates the the type of fire door.

Q-Mark fire doors are clearly marked as such by small plastic plugs in the door leaf and/or frame, these include member details and scope of certification for verification purposes during specification, installation or at a later stage in their service life. They are only available to full members of the BM TRADA Q-Mark schemes.

The plugs follow a simple colour coding system and for more details go to their website BMTRADA This information is summarised on a laminated plastic card, available free of charge from BM TRADA, contact enquiries@bmtrada.com).

British Woodworking Federation Certifire fire door scheme

British Woodworking Federation (BWF) is another major organisation that provides fire door ratings. Their fire ratings for fire door assemblies are stated in minutes and prefixed by the letters ‘FD’ i.e. FD 30 equates to a 30 minute fire door or fire doorset.

The most commonly specified integrity levels are:

• FD30 – 30 minutes (Half Hour)
• FD60 – 60 minutes (One Hour)
• FD90 – 90 minutes (Ninety Minutes)
• FD120 – 120 minutes (Hundred and Twenty Minutes)

As part of the steps being taken by the BWF to simplify fire door identification and eliminate confusion in specification, the existing FD20 rating is no longer available.

Every BWF-Certifire Fire Door Assembly carries a permanent and tamper evident label. For more information go to their website The British Woodworking Federation or go to FDS_Directory_2009.

The former system used by BWF utilising plastic plugs is no longer used but may be found in older buildings. The obsolete fire door identifications can be seen on the BWF obsolete card.

Nominal Fire Doors

Nominal fire doors are doors that are not certified but in the opinion of an assessor will hold back a fire for a specified period of time. Identifying nominal fire doors is very difficult but there are a number of clues that may indicate the door is a nominal fire door.

All dedicated fire doors providing a half hour or greater performance are usually fitted with intumescent seals. These may be encased in a PVC sheath, of any colour, which may also hold a blade or brush seal for smoke sealing purposes. These seals are fitted in the door leaf edges or the frame to seal the head and long edges of the assembly. A door may be fitted with a concealed intumescent system where the long edge sealing is housed under lippings. Intumescent seals will be visible at the head of the door. Doors 44mm thick fitted with 10-15mm wide intumescent seals are likely to be FD3O and doors 54mm thick using at least 20mm width of intumescent seal, fitted as one or two strips are likely to be FD6O.

Fire doors with a rating in excess of FD6O are rarely used on escape routes or to protect people but may be found where property protection is important e.g. data storage areas where documents cannot be removed in the event of fire. Some of these doors have the appearance of timber, but may be constructed with a mineral core. Expert assistance may be required to identify such doorsets.

Fire door jambs need to be over 25mm wide.

Older panel doors, especially if less then 44mm thick, are unlikely to be FD30 however they could have been upgraded or modified to achieve a fire resisting standard. These days you might find certified panelled fire doors with wood surfaces to fit into traditional homes.

Hollow flush doors using egg box or similar construction will not be FD30. This can be detected by the weight of the door because fire doors are much heavier than a hollow door. To check the weight of a door, instead of removing it, you can detach the self closer and swing the door between you thumb and index finger this gives a good indication of the weight of the door. Hollow doors are reasonable easy to detect using this method.

Fire doors will have door closers fitted. Spring-loaded self-closing hinges and concealed Perko door closers with chains might have been utilised.

Because of the weight of a fire door and to prevent it warping, fire doors are usually fitted with three fire door hinges. However the current BS EN standard does allow two hinges in certain circumstances. There may be documentation that was supplied with a fire door giving you all the necessary information. Unfortunately, there is no standard method of identifying fire doors other than the Q-Mark or the Certifire fire door schemes therefore insisting on written proof that a door meets all the necessary standards, for example a test certificate, might still be necessary.

Fire Door Seals or Fire and Smoke Seals

Intumescent fire door seals with or without cold smoke seals should be fitted to the back edge, stile and head of the fire resisting door sets. The following is information on the type or size of intumescent fire door seal that should be used.

Not all intumescent materials act in the same way. Low pressure seals expand in all directions but provide little help to the door in resisting distortion under fire. Some high pressure seals exert pressure mainly in one direction and provide some resistance to distortion of the door leaf under fire. A further type of intumescent material, available in different grades, acts in all directions and generates some pressure. Fire door seals activate at temperatures that are above human survival levels.

In most circumstances, retention or control of smoke is required, where this is so, fire door sets must be fitted with appropriate smoke seals. These prevent the leakage of air and therefore smoke through the most vulnerable places i.e. gaps between door and frame, glazed openings and where appropriate, letter plates. Installations fitted with such seals are designated by the suffix ‘s’ after the Integrity rating i.e. FD 30s.

To achieve this, such classifications are given tests on the seals in accordance with BS 476 Part 31.1 or Certifire approved smoke seals to TS21.

Note: – It is always best to ask fire door manufacturers what type of seal to use.

Fore more detailed information go to Intumescent Fire Seals Association

Fire Resisting Glazing

Glazing may range from a small vision panel in a door to a glazed screen for maximum light transmission and safety. Ordinary glass cracks when exposed to heat and is liable to fall out fairly early in a fire. Fire resisting glass can withstand exposure to the heating condition in a fire test for at least 60 minutes before it reaches a temperature high enough to soften it. The main reason for this is that in clear FR glazing nearly 50 per cent of the incident heat is transmitted through the glass by radiation.

The size of the glass and the method of its retention are important factors which influence its integrity. As the temperature approaches the softening point a large sheet will tend to collapse earlier than a smaller one. On the unexposed face, beading retaining the glass is subjected to radiant and conducted heat through the glass and to convection currents at the top of the pane.

This can raise the temperature sufficiently to ignite timber beading after about 20 minutes. To delay the ignition of beading to 30 minutes it is necessary to provide protection by impregnation of a surface coating or a surface covering of non-combustible material or fit a fire resistant glass secured using a fire resistant glazing systems which hold the glass firmly in place during normal use, but in the event of fire the intumescent material expands securing and insulating the glass and protecting the surrounding timber.

For longer periods of fire protection, an improved retention system for the glazing is needed, The glass panel should be small and the method of fixing it should ensure that no direct path can be created for the transference of hot gases.

Fore more detailed information go to Glass and Glazing Federation and download Fire Resistant Guide.

Existing doors

Years ago it was accepted practice to improve the performance of an existing door to a half-hour fire-check or fire-resisting standard, although in some cases it was more economical to replace the door rather than alter it. The doors were usually panel type or a light core flush type about 44mm thick: they require a facing on the risk side with a non combustible board.

It is now the accepted practice to fit new fire doors and fire doorsets preferably to upgrading them.

These days you can configure and order entire fire doors with 30 minutes protection (FD30) online. These fire doors can be configured with or without frame.

Suitability of doors for upgrading.

Door type	Suitable?	Comments
Unframed, hollow core, flush	No	Too light and insubstantial
Framed, hollow core, flush
Framed, solid core, flush	Yes	If core of flaxboard, timber or solid chipboard
Ledged and braced	No	Insufficient thickness at the edges to accommodate an intumescent seal
Framed, ledged and braced	Yes (20 min only)	Extremely dependent on joints and fixings
Framed, solid with solid panels	Yes	Depends on thickness, minimum 44 mm, and panel construction
Framed, solid with glazed panels	Yes	Depends on thickness, minimum 44 mm and type/installation of glazing

Methods of upgrading

There is no ‘one size fits all’ method of upgrading existing doors and the solution chosen will depend on the door construction, condition, situation and customer requirements. Techniques that have been successfully used in the past include:

Facing the door leaf with a non-combustible board

This is one of the easiest methods of upgrading, although it does create a visually unattractive result. It is, however, favoured by some heritage authorities as it a reversible process; removing the facing returns the leaf to its original condition. If used, facings should be applied symmetrically to each face (note that the increased thickness and weight may affect the door frame and ironmongery specification).

Sandwiching panels

For paneled doors, the weakest area is generally the panel itself. In many cases the timber will be less than 10 mm thick at the thinnest point. One method of upgrading is to remove the panels, split them through their thickness and insert a sandwich material, either an appropriate intumescent sheet or a non-combustible board. This is more difficult than other approaches but does enable the original finish to be maintained, which can be important for heritage projects.

Intumescent paper

Intumescent paper and card can be used to selectively protect vulnerable areas such as the fielded area of paneled doors. The application thickness is controlled by the thickness of the paper but can be veneered to restore a timber finish.

Intumescent paints and varnishes

Intumescent paints and varnishes are available for use on timber-based fire resisting doorsets where a maximum performance of 30 minutes integrity is required. These products require extremely specific application techniques and are reliant on the underlying condition of the doorset construction. Great care should be taken to ensure that full-scale test data for the product is both available and appropriate for the application in question.

It is likely that other upgrading measures will be required in conjunction with any of these measures.

For more information download the following documents.

Upgrading’s doors English Heritage Upgrading doors Inter nation Fire Consultants Ltd

Fire Door Furniture and Ironmongery

An important aspect of ensuring fire doors meet the required standard, is the fitting of certified door furniture, which is overlooked on many occasions. If you go to Fire Door Fittings and Ironmongery there is a detailed description of all the door furniture suitable for fire doors and the appropriate standards.

Maintenance of Fire Doors

Fire doors are engineered products that provide life and property saving functions in the event of fire. It is important that they are regularly inspected and maintained to permit them to perform at their best on the one and only occasion when they are called upon so to do.

Doorsets fitted with hold open devices or swing free type closer should be closed daily, particularly overnight when there is likely to be low building occupancy. For busy 24/7 buildings (e.g. hospitals) fire doors should be closed at least weekly. All fire doors should close effectively from any angle of opening using only the door closer.

There are a number of reasons why doors may fail to close:-

• Check that there are no foreign bodies or other objects obstructing the door.
• Check that any smoke seals are correctly fitted and are undamaged.
• Check the latch, if fitted to ensure correct operation and that it is suitably lubricated.
• Only as a last resort should the closing device be adjusted, but this must be carried out carefully to ensure that the doors can be opened without undue force.

Intumescent seals should be checked regularly, at intervals not greater than 6 months, and damaged or missing seals replaced. To maintain the design performance potential, replacement seals should be of the same brand, size and type as the original. However, any intumescent seal of the same size as the original is better than none.

Mechanical items such as hinges, locks, latches, closer, floor springs etc are likely to wear over time. Maintenance provisions should comply with the hardware suppliers recommendations where these are known. Otherwise, locks and latches may require occasional light lubrication.

Some hinges use self lubricating bearings that will not need additional lubrication.

Where it is necessary to replace worn hardware on a fire door, the essential items should be replaced with products to the same specification as the original where possible. Otherwise hinges, latches, locks, flush bolts, closer and other items of load bearing or securing hardware should be of the same type and size as the original items and should have been proven for use in timber fire rated doorsets of the required performance. Hardware that has been successfully tested in metal doorsets may not be suitable for use with timber doorsets. Intumescent gaskets may have been used under hinge blades, lock/latch for end plates, strike plates, with some closer fittings and in flush bolt recesses. These gaskets should be replaced if possible with gaskets of the same material.

Otherwise they should be retained and reused with the new fittings if they are undamaged. Intumescent gaskets or mastics used for these applications are usually the low pressure type.

Redundant hardware should be carefully removed.

Decoration

Unglazed areas of any fire door leaves are generally not required to provide a specific surface spread of flame requirement and may therefore be decorated as desired. There is no evidence to suggest that over painting of heat activated seals has any detrimental effect on the ability of the seals to perform efficiently. There are some benefits in over painting the seals as they are less likely to absorb atmospheric moisture. However, there are limits on how much paint can be applied without there being a risk of the seal being rendered inoperative. It is recommended that over painting be limited to a maximum of five coats of conventional oil bound paint or varnish. When preparing a frame for redecoration, the use of heat or chemical strippers should be avoided if intumescent seals are incorporated. If seals are damaged by either of these processes, they should be replaced. If glazing beads have been painted with intumescent paint, it is essential that they should be repainted with a similar paint.

British Standards

The following is a list of documents relevant to timber fire doors BS 476: – 20: 1987 Fire tests on building materials and structures. Methods for determination of the fire resistance of elements of construction (general principles)

BS 476 – 22: 1987 Fire tests on building materials and structures. Methods for determination of the fire resistance of non-loadbearing  elements of construction

BS 476: – 23: 1987 Fire tests on building materials and structures. Methods for the determination of the contribution of components to the fire resistance of a structure

BS 476: – 31.1: 1983 Fire tests on building materials and structures. Method of measuring smoke penetration through doorset and shutter assemblies – method of measurement under ambient temperature conditions.

BS 8214:2008 Code of practice for fire door assemblies

BS EN 1634-1:2008 Fire resistance and smoke control tests for door, shutter and, openable window assemblies and elements of building hardware. Fire resistance tests for doors, shutters and openable windows which is an alternative for BS 476 – 22: 1987

Additional Information

Building Research Establishment (BRE) produce research documents called BRE Digests and one on fire doors has been produced. BRE Digests are obtainable from BREbookshop use the website search engine.

If you require a more in depth information check out Architectural and Specialists Door Manufacturers Association and download the Best Practice Guide to Timber Fire Doors.