The trouble with insulated fire curtains
It wouldn’t be an exaggeration to say that five times a week, a phone call or a fire strategy report and a fire curtain or fire curtains and smoke curtain specification lands on my desk with the requirement for insulated fire curtains or fire curtains tested with an insulation zone. From Building Control in Southampton, to an architectural practice in Singapore, the same question comes up time and time again.
“Do you manufacture fire curtains with 60 minutes, 90 minutes or 120 minutes integrity AND insulation? Or what are the EIs of your Flameshield fire curtain range?
Within overall fire resistance criteria, where E = Integrity and I = Insulation, the requirement is for EI 30, EI 60, EI 90 or EI 120. Now I know what is trying to be achieved - namely a fire curtain that will provide 30-120 minute integrity and protection from spread of flames and hot gases (E 120), coupled with defined measurements to prevent fire spread by spontaneous non-piloted combustion and radiation (total heat flux) and to protect people and property against exposure to high temperatures and associated risks.
The answer is that none of the leading Fire Curtain UK manufacturers produce an insulated fire curtain or a fire curtain with insulation properties to EI 30.60.90 and 120 minutes. They certainly should NOT be advertising such performance characteristics. Insulation properties (i.e. EI) are simply not available with fire curtains in the UK. If you think otherwise, please feel free to touch a millimetre thin fire curtain on it’s surface after 60 or 120 minutes. (And apologies to our European friends who still use this term although predominantly for insulating zone, or EI1 (tested at 25mm) and EI2 (tested at 100mm) this is a UK-centric article.) The only UK exception to this would be in conjunction with a sprinkler system but nobody is further than a desk top appraisal on this.
The misnomer associated with an insulated fire curtain was worsened with the misconceived introduction of an insulating zone for fire curtains in PAS 121 which mercifully was confined to the annals of fire curtain history and totally scrapped in July 2013 so the confusion is understandable. Updated and precise guidance is now available in BS 8524-2.
The reasons why are common sense, but do not worry about your project, there is good news and a documented alternative and clear guidance as to the use of radiation and radiation tenability data (instead of insulation) in the UK’s preeminent fire curtain standard BS 8524-2, Active fire curtain barrier assemblies – Part 2:Code of Practice for Application, Installation and Maintenance.
Page 13, 5.3.1 states that “Barrier assemblies replace static partitions and therefore have to descend within a clear space. Therefore the problems of surface temperatures DO NOT APPLY, but integrity, radiation and occupant tenability is still relevant.” A further note states that “Where it is impracticable to fix or hang thermocouples to the surface of the test specimen, as it would prevent the intumescent process working, the insulation performance of the specimen cannot be determined and the barrier assembly can only be tested for integrity and radiation.”
5.3.2.1 of BS 8524-2 continues, where radiated heat flux as opposed to insulation, is to be used to assess whether conditions are tenable, three distinct approaches should be used :
simplified approach for horizontal routes in dwellings (which can be explained based on the guidance in BS 8524)
fully fire engineered approach for horizontal escape routes (which I am not qualified to explain) but the guidance is on page 25 of BS 8524-2 with the important data and matrices on subsequent pages.
fully fire engineered approach for all other applications
I should definitely draw your attention to two pages of data B1 and B2 which provides permitted radiation performance, R maxA and accounts for minimum separation between escaping occupants and barrier assembly, d separation and speed of escaping occupants, v occupants. These indicate the performance criteria required from a fire curtain to achieve the requisite tenability. The definitive conclusion is that if your project requires active barrier fire curtains to form an exit route, they will definitively require testing to E for integrity and W for radiation so EW 30/60/90/120 not EI.
BS EN 13501-2 2016 also provisions for products to be classified as E or EW without insulation.
5.22.1 General states that, “Classification for integrity (E) shall be according to whether or not the element is also classified for insulation (I, I1 or I2). Where an element is classified both for integrity and insulation, the value of integrity is that determined by whichever of the three aspects fails first. Where an element is classified without an insulation classification (i.e. for the classifications E, EW, RE and REW), the value of integrity is that determined by the time to failure of only the cracks/openings or sustained flaming aspects, whichever fails first.
All A1S Group fire curtains are actually witness sampled, cyclic tested and furnace tested by Warrington Exova and within the test documentation is key radiation data, particularly kw/m2 at fifteen minutes and time elapsed before radiation reaches 15 kw/m2.
AS A NOTE THE A1S GROUP HAVE NOW SUCCESSFULLY TESTED THE UK’S FIRST EW120 CURTAIN, TO C1 CLASS WITH WARRINGTON FIRE WHICH ACHIEVED A UK INDUSTRY LOW 2.62 KW/M2 AT 15 MINUTES. 6.30 KW/M2 AT 1 HOUR AND 10.71 KW/M2 AT 120 MINUTES.
Hopefully, this article will complement the information you as a fire engineer or architectural specifier require for using the correct radiation data instead of the now defunct and highly confusing insulation data. Extended data sets including radiation minute readings between 0-120 are available on request to help establish which Flameshield fire curtain or indeed whether our product is even suitable for your application.
For details of A1S Group industry leading fire curtain radiation readings, must have test data and any general enquiries, please contact info@a1sgroup.com
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