The fire door is a highly engineered construction product that when assembled and installed correctly plays a vital and integral part of the fire strategy within any building. Whilst providing and maintaining fire performance, exterior pedestrian fire doors have to provide other essential roles including security, thermal performance and weatherability to comply with Building Regulations.
The installation of the fire door is critical to ensure that the door maintains equal fire performance to that of the tested or assessed system. The distance between the door leaf and supporting construction should be as tested or assessed, any fire-sealing mediums used and detailed in the test report or assessment should be used to reinstate the fire performance of the door assembly.
The perimeter gap between the door leaf and the supporting construction is typically oversized to allow for ease of installation of the door set within the construction. Perimeter gaps can be exploited by fire if not adequately protected or fire-stopped.
In the UK, approximately 95% of all fire foams currently marketed as Fire Door Installation Foams have not been tested for the sealing of linear joints in accordance with BS476: Part 20/22 (ad-hoc principles) or EN1366-4 +A1:2010 (Fire resistance tests for service installations).
Polyurethane foams (PU) are normally expelled from pressurised cans through nozzles as a viscous liquid, which expands rapidly to typically 40 times its original volume to form a rigid foam. PU foams require moisture to be present in the environment for the foam to set, after which it can be cut and finished, depending upon the application. Polyurethane foams are often coloured pink or grey to distinguish themselves as a fire-sealing medium.
As explained earlier, it is critical to ensure that the product is fit for purpose and has the required level of supporting test evidence to achieve the required period of fire resistance. Therefore, a foam tested for linear joints, tested in a concrete-to-concrete application, is not suitable for use around a gypsum wall partition or a timber fire-door frame.
Are all coloured foams the same?
No, B1 or B2 foams are typically coloured to differentiate between fire and non-fire rated. B1 or B2 products are often supplied in pink and are inherently fire resistant, whereas straw or neutral coloured foams are non-fire rated and used principally for general gap filling.
There is a common misrepresentation regarding the colour of such foams, Fire-rated foams can be easily pigmented during the manufacturing process, with no significant costs. The pigmentation has no direct correlation with higher performance in terms of fire resistance or behaviour under fire conditions.
How to select the most appropriate fire rated foam
Given the variety of sealing mediums available, it is critical to ensure that the sealing system is used in accordance with the test evidence or field-of-application report. Elements used within the system, such as the packers are critical and play a vital role. Reactive components such as intumescent packers need to be used and not changed or substituted without further test evidence being proposed.
Ancillary components used for installation
Polymeric packers, which are typically produced from polypropylene (PP) or polyethylene (PE) are reported to be a concern when exposed to fire conditions, but this is simply not the case and sufficient test evidence is available to contradict this misconception. Whilst PP or PE do support combustion, tested door-set assemblies have proven that such components can be successfully used with or without combustible architraves. Again, PE and PP polymers do not migrate oils and are considered chemically inert.
Intumescent packers are often produced from a polyvinyl chloride (PVC) plasticised polymer, which is impregnated with expandable graphite and exhibits a flexible characteristic. The flexibility of such polymers is achieved by plasticisation oils used in the compounding process. Such processing oils used in this process can migrate from the base polymer and as such may result in softening of the foam when exposed to prolonged exposure and a loss in mass may be experienced. Plasticiser migration can also affect the fire performance of the product. When tested on a hotplate such material can easily ignite and support combustion when exposed to direct flame impingement.
It is critical again to ensure that the right packing material is used and remains as tested.
Do I need to cover the foam?
PU foams are extremely sensitive to ultraviolet radiation and when exposed to certain conditions can deteriorate rapidly. The first sign of such deterioration is exhibited by the colour and pigmentation contrast. Secondly, cellular degradation can also be apparent, and if the cell formation becomes friable and easily damaged, the long-term durability needs to be seriously considered.
Which suppliers provide test evidence to back up their claims?
Marketing statements can be extremely compelling. Without robust evidence, however, they are pointless. Ask your shortlisted suppliers to back up their claims. Do they have independent test evidence or a reputable engineering report? Does third-party certification exist to provide assurance?
In addition to these assurances of performance, consider suppliers that will offer you expert guidance. And if they understand the regulatory requirements in your geographic region, this can be a huge added benefit to keep your building project on track.
Expert help and advice are available
I started by highlighting the technical complexity of passive fire protection. There are many specialist associations in existence that provide independent advice and guidance to any relevant industry parties. They exist to help you deliver an effective outcome where fire safety is concerned. Many competent manufacturers and suppliers will be members of these associations, proactively contributing to the wealth of knowledge and expertise available. By drawing on such invaluable resources, your project will meet the approval of the authorities first time and avoid frustrating delays in progression. Most importantly, it will be equipped to slow the spread of fire, should it ever break out.
Fire and Acoustic Seals Limited are specialists within the passive fire-protection industry and are approved suppliers to the British Woodworking Federation (BWF), along with being members of the Architectural and Specialist Door Manufacturers’ Association (ASDMA). Innovation is at the heart of their business and they are constantly striving to further the solutions available to the industry.
For more information, go to www.fireandacousticseals.co.uk