Peter.L.

Thanks again, Tom. You're absolutely right about attitudes and this particular area of risk will always be one that gets less scrutiny. I have long had concerns about the lack of a joined up approach in commercial fit-outs where fire protection measures are concerned. Fire barriers span the entire storey height and include partitions/doors between ceiling and raised access floor but also include the ceiling and floor void barriers, the ceilings and floors themselves and also the interfaces between those various elements. There seems to be very little interrogation of the finished construction as a whole barrier and a presumption that the respective 'specialist sub-contractors' have done what they should have done. For example, there are plenty of 60 minute fire screens out there fixed on a raised access floor. That's a very heavy concentrated load and it's highly doubtful that the floor system will have been through a fire test, adequately loaded and to the same intensity. I know of one floor system that is highly specified in commercial interiors and has been fire tested, BUT only for 30 minutes, to the reduced 500 degree C temperature curve, and with only a moderate, evenly distributed load. That seems very incompatible to me. Back to carpets, my friends at Warrington Fire certainly take the view that carpets should be either terminated either side of a fire door or at least have a non-combustible threshold placed over the carpet. That's the same risk-averse approach that I favour. after all, we can't be certain of where and to what intensity a fire might be present. But as you say, the decision rests with the enforcement officers, so I guess we'll just have to include some form of disclaimer. Thanks again for your thoughts. They've been very helpful. Peter

Thanks for the response, Tom. My interest is in the supply and installation of steel-framed glazed fire doors. We have no control on the floor finish specification and the fit-out industry is not presently very joined up in this context. A slab to slab fire barrier could comprise a ceiling void barrier; the false ceiling itself; a glazed door/screen; the floor finish (carpet); a raised access floor; a void barrier under the raised access floor. Whilst all the responsible parties in that list may well be very happy with their own test/certification paperwork, the joining up of all these elements to ensure the whole finished construction works is very poor. Fire doors are fire tested with a defined clearance gap to a non-combustible threshold. How the door behaves in that test is not representative of a door in the field, fitted with the same clearance gap but over a carpet. BS4790 is clear that it is "not intended to assess the contribution a textile floor covering will make to an established fire". So is that suggesting that if there is the risk that the carpet might be alight, it should not be allowed to pass beneath the door and that there should be some form of non-combustible threshold? That is alluded to in BS 9999 for floor coverings in fire-fighting shafts which suggests that floor finishes which cannot be assured to be non-combustible should "be interrupted at all doors to and within the fire-fighting shaft along the line of the threshold of the doorway with a metal or other non-combustible strip not less than 50mm wide". That suggests to me that there is a perceived risk of fire passing under a door, especially where it has no form of threshold seal (intumescent or otherwise) and if that is the case, surely it should apply wherever fire doors are specified. I'd be interested in your thoughts.

Hello all, I would be very interested in your thoughts on this matter. When we fire test steel framed glazed fire doors, the sample is installed with a simple base clearance gap to the supporting construction, usually a concrete beam or build-up of concrete blocks. The outcome rarely involves an integrity failure at the base, simply because there is nothing combustible there. In the field, the expectation will be that some form of floor finish will be laid over the floor and that the tested clearance gap will be set against the finished floor. Presumably there is no firm guarantee that the carpet will not ignite, nor how close to the door this might occur, so is there any guidance on whether this is an acceptable practice? PL