In our final article on Fire Doors, Modern Doors are investigating the components of a Fire Door set.

Components

The BWF (British Woodworking Federation) Certifire Fire Door and Doorset Scheme have put great efforts into raising the awareness and understanding of the importance of compatibility of components within Fire Doors. Fitting an incorrect size component or material that has not been specifically designed to be used on a fire door could significantly affect the performance of a fire door set.

The quality of the door hardware/ironmongery is essential in keeping the fire door in place in the event of a fire. Door closers, hinges, locks and latches are all considered essential ironmongery and must therefore carry fire test evidence to show their suitability. Cutting an aperture in a fire door creates a weak point that is most likely to fail if not filled with certified products. Along with glazing, the use of letter plates, air vents and spy holes are also common and these products will generally be required to be installed in conjunction with intumescent seals, pads or paste in order to maintain the certification.

Contemporary Walnut Glazed Fire Door

Glazed apertures are often required in both internal doors and external doors to fulfil the requirements of Part M (the minimum standard by which buildings should be made accessible to, and usable by everyone, including people with disabilities) of the Building Regulations but are regularly used to improve the vision around a building, as well as for maximum light transmission and safety. Ordinary glass cracks when exposed to heat while fire resistant glass can withstand exposure to the heat condition in a fire test of at least 60 minutes before it reaches a high enough temperature to soften it. Two main types of fire resistant glass are Pilkington Pyrodur and Georgian wired glass. Even the size of the glass and the method of its retention are important factors that 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. For this reason when putting glazing into a fire door using the correct bead is as vital as using the approved intumescent glazing system and glass. Even when pinning or screwing the beads it is important to do so at the correct angle to ensure that if the bead burns away, the pins/screws will still hold the glass and seal in place. These operations therefore can only be carried out by the door manufacturer or Certified Licensed Converter or the door certification will be invalid. Fitting glazing should therefore never be done on site.

Fire Door Construction

It is important to note that no longer are fire doors only available in solid timber construction. Manufacturers of fire doors now produce the doors using safer, more cost effective materials from sustainable sources. While solid timber fire doors are still available, flaxboard and wood composite door cores form the basis of the majority of constructed fire doors manufactured by scheme members. With the advantage of reducing the weight and cost of a fire door while still allowing the door to burn at a slow consistent rate. The door core is then covered by a moulded skin, veneer or laminate to suit the choice of the buyer and building’s interior.

Can existing doors be upgraded to fire resistant standard?

The most cost effective option for a fire door is always advisable to fit from new, however an upgrade to FD30 status is sometimes possible depending on the construction of the existing door. The door should have a solid timber or chipboard core, be at least 44mm thick and come with a sound frame that is capable of bearing the additional weight of the upgraded door. An unpainted door can be painted with intumescent varnish or paint to manufacture specifications and a painted door can be covered with an intumescent membrane with fireproof wood veneer facing. If glazed the glass panel (s) must be replaced with fire rated glass. The upgraded door must be re-hung with at least three fire protected hinges in order to prevent warping which would severely compromise the integrity of a fire door. Finally other modification such as the addition of intumescent seals will also be necessary.

In our third article of four, Modern Doors are going to discuss fire door certification in more depth.

Certification

Just like fire doors, all passive fire protection products are potentially life-saving, and with this in mind third party certification involving independent testing and auditing should be the minimum standard demanded for every building. The performance of timber doors is assessed by subjecting them to a standard test procedure specified in BS 476: part 22:1987 or BS EN 1634-1: 2000. Tests are made on complete door assemblies including door and door frame and all the requisite hardware (e.g. locks, latches, hinges etc.) We will refer to this as a ‘door set’, which is fixed in a wall to represent its use in practice with the door face then exposed to heat conditions that would be anticipated in a fire while observing the door for both stability and integrity. To conform to British Standards tests are required to be carried out with the upper part of the door under a small positive pressure which simulates closely 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 unexposed side of the door to see when it ignites. Of course fire doors are tested from each side to establish their level of performance with either face exposed to fire conditions.

A weak point surrounding fire doors is on its edges and for this reason 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 seals are about 4mm thick by 10mm 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 deg C, usually about 10-15 minutes from the start of a fire, the seal swells and seals the gap around the door.

Manufacturers can certify fire door sets, both for identification purposes and to guarantee their performance in a fire situation. This door set will then be tested by an approved fire testing centre and once approved each similarly constructed door set will be identified by a label or colour coded plug usually affixed to the top edge of the door.

Timber Fire Door Plugs

The woodworking association, BM Trada, uses a system known as Q-Mark, in which a series of coloured plugs is inserted into the door to indicate the fire door type, the member details, the scope of certification during specification and installation and service history. As well as BM Trada the British Woodworking Federation (BWF) is another major organisation that provides fir door ratings. Their fire ratings for fire door assemblies are stated in minutes and prefixed by the letters FD e.g. FD30 refers to 30 minute fire doors or fire door sets. The most commonly specified integrity levels are:

FD30 – 30 minutes

FD60 – 60 minutes

FD90 – 90 minutes

FD120 – 120 minutes

In this, our second article in this series, Modern Doors will be providing information surrounding fire safety with an accurate description of fire doors.

Fire Safety & Protection

It is the aim of all products used in fire safety to restrict the spread of fire by containing it to one area or compartment. For this reason there are both passive and active fire protection products, however it is important to note that in order to have an effective fire protection system both these systems need to be designed and installed in combination working effectively together to restrict the spread of fire.

Active fire protection products such as alarm systems, fire extinguishers and sprinklers are an important aspect to a fire safety plan with an important role of warning occupants and assisting in controlling a fire until the fire services arrive. This can often lead to the assumption that an active system on its own is the most effective means of increasing fire safety in a building. In the majority of cases however active systems are designed and incorporated into a building with the assumption that passive fire protection products will also be in place and will achieve their performance rating.

Fire Escape Internal Door Sign

Fire Escape Door Sign

As we stated previously passive and active systems need to be designed and installed in combination to form an effective fire protection system, as only installing active systems would allow a fire to run unchecked through a building leading to potentially disastrous consequences. For this reason a fire door has a critical role to play in any passive fire protection plan. Buildings are compartmentalised to delay the spread of fire from one area to another and these compartments are usually linked by fire doors to allow the flow of traffic around the building. Fire doors have two important functions in case of a fire; when closed they form a barrier to stop the spread of fire and when opened they provide a means of escape. Thus by using an early warning system, containing a fire within a small compartment and providing methods of controlling or extinguishing a fire, you then have the most effective method of protecting property but more importantly lives.

What is a Fire Door?

A fire door as defined by the ASDMA (Architectural and Specialist Door Manufacturers Association) is “A complete installed door assembly comprising doorframe, door leaves, other panels, hardware, seals and any glazing that when closed is intended to resist the passage of a fire and smoke in accordance with specified performance criteria. A fire door = a complete installed assembly.”

Brown Fire and Smoke Internal Door Seal

Brown Fire and Smoke Door Seal

A well designed timber fire door will delay the spread of fire and smoke without causing too much hindrance to the movement of people or goods. Every fire door is therefore required to act as a barrier to the passage of smoke and/or fire to varying degrees depending upon its location in a building. In order for this to happen it must be fitted with intumescent seals which remain dormant under normal conditions but expand greatly in the heat of a fire to close the gap between door and frame. As smoke spread is an even greater threat to life and property than flames, fire doors should also be fitted with a ‘cold smoke’ seal to prevent the ingress of smoke around the door edges. It is important to mention that some fire doors only require intumescent seals whereas other fire doors may have to resist the passage of smoke as well as the spread of fire.