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Buildings are compartmented 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. Doorsets 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 fire to varying degrees dependent upon its location in a building and the fire hazard associated with the building. Consequently the functions of a fire doors is, to provide adequate resistance to the passage of smoke and other combustion products during the early stages of a fire. Secondly to provide a barrier to a well-developed fire without permitting fire and excessive quantities of smoke to pass. Some doors may be required to fulfil only the first function as they may not be subjected to the full severity of a fire because of their location; others may have the main aim of resisting fire penetration as indicated by the second function. Some may have to meet both requirements. At present, fire doors are specified as smoke-stop doors when required to fulfil the first function and fire-check and fire-resisting 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 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 door by the use of a combustible fibrous pad on the un exposed side of the door and see when it ignites. A 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 strip 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 strip, about 4 mm thick by 10 mm wide, cut into a groove in the door or the frame edge. As soon as the temperature in the vicinity of the strips exceeds 200 degrees C, usually about 10-15 minutes after the start of a fire, the strip swells and seals the gaps. One strip is adequate for a half hour fire door and for the increased protection needed with one-hour doors, two of these strips will be necessary. The intumescent material is soft and cellular in structure and will not prevent deformation of the door.

There are fire resisting 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.

[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

Identifying fire doors is very difficult, however responsible door manufacturers label their doors. 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, or in addition to, the label. Identification labels are usually fitted on the top or hanging edge of the door and plugs in the long edges. 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 are sometimes removed during installation, or adjustment of the assembly and may have been painted over.

All dedicated fire doors providing a half hour or greater performance will be 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. Intumescent seals expand under heating to seal the gaps between the door leaf and the frame and at the meeting stiles of pairs of doors.

Doorsets using 44mm thick doors fitted with 10-15mm wide intumescent seals are likely to be FD3O doorsets. When used with 54mm thick doors using at least 20mm width of intumescent seal, fitted as one or two strips, the design performance for this doorset is likely to be FD6O. Doorsets 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.

You may have documentation that is supplied with the fire door giving you all the necessary information. Unfortunately there is no standard method of identifying fire doors other than insisting on written proof that a fire door meets all the necessary standards, for example a test certificate.

The woodworking association 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.

This information is summarised on a laminated plastic card, available free of charge from BM TRADA, contact Simon Beer (01494 569821 or sbeer@bmtrada.com).

British Woodworking Federation is another organisation that provides fire door ratings and the following is their system. Fire ratings for fire door assemblies are given in minutes and prefixed by the letters 'FD' i.e. FD 30 equates to a 30 minute fire door or doorset. The most commonly specified integrity levels are:

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 and/or plastic plug. For more information go to their web site.

The former system used by BWF is no longer used but they may be found on older installations.

Intumescent Fire Seals and Cold Smoke Seals

Intumescent fire seals and 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 strip 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 seals activate at temperatures that are above human survival levels.

Type of fire door	Without cold smoke seals	With cold smoke seals
30/30 Single action door 30/30 Double action door	10mm x 4mm (Both sides & top)	10mm x 4mm (Both sides & top)
30/30 Double pairs of doors	10mm x 4mm on one centre stile 10mm x 4mm on other stile, heads and back edges
60/60 Single action door 60/60 Double action door	20mm x 4mm (Both sides & top)	20mm x 4mm (Both sides & top)
60/60 Double pair of doors	20mm x 4mm on one centre stile 20mm x 4mm on other stile, heads and back edges

In most circumstances, retention or control of smoke is required, where this is so, fire door sets can 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 Certified approved smoke seals to TS21.

All hinges, locks and door closer's should be fitted with Intumescent material. Grooves should be made slightly wider than the seals to allow of pre painting and shrinkage of timber. Please refer to fixing and installation instructions.

Fire Resisting Glazing

Glazing may range from a small vision panel in a door to a glazed screen for maximum light transmission. Ordinary glass cracks when exposed to heat and is liable to fall out fairly early in a fire. Wired glass 6 mm thick 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 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.

For longer periods of fire protection, an improved retention system for the glazing is needed, so far only non-combustible glazing sub-frames have been shown to be satisfactory. 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.

30/30 using hardwood beading – 10mm X 4mm each side of wired glass
60/60 using hardwood beading – 20mm X 4mm each side of wired glass plus a lining

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 each side with a non combustible board.

It may be necessary to replace existing damaged door leaves or doorsets and in some cases, to install additional fire rated doorsets. It is now the accepted practice to fit new fire resisting doorsets preferably to upgrading them.

There are ASDMA members specialise in the manufacture of bespoke performance doors and doorsets to suit customer defined requirements. Associate members can supply many of the doorset related materials and components. For further information please refer to the ASDMA website.

There is no advice on improving the performance of existing doors to a one-hour standard.

However there are occasions when it is acceptable to upgrade doors to a half hour standard and advice is available.

Suitability of doors for upgrading.

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:

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).

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 labour intensive than other approaches but does enable the original finish to be maintained, which can be important for heritage projects.

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 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 these paints and varnishes.

Maintenance of Fire Doors

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.

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 listed above 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.

Redundant hardware should be carefully removed. 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.

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 in accordance with clause 21. If glazing beads have been painted with intumescent paint, it is essential that they should be repainted with a similar paint.

British Standards

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 8214:1990 Code of practice for fire door assemblies with non-metallic leaves

Costs

There was a time when cost of a fire safety solutions was never considered and the fire safety schemes were simple based on the current codes. It was up to the employer to consider this aspect and obtain the best cost effective solution. Since the introduction of risk assessment and the numerous solutions available to the fire safety profession it is now incumbent on the person conducting a fire risk assessment to consider costs. This can be achieved by comparing prices on the net and arriving at an average price and you must also consider the cost of installation. In this case a starting point could be the fire door configurator at SafeLincs .

Additional Information

Building Research Establishment They produce research documents called BRE Digests and one on fire doors has been produced. BRE Digests are published for the Building Research Establishment by Her Majesty’s Stationery Office. They are obtainable from Government Book shops, or through book-sellers. Digests are NOT sold by the Building Research Establishment.

Note for Guidance

The Fire Safety Advice Centre

Fire Check and Fire Resisting Doors

Introduction