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Fire doors
from:Fire doors look deceptively like any other door, but their job is to save lives. To do this, however, they must be correctly specified, installed and used, as Peter Freestone of Kidde Fire Protection Services explains for FMJ Magazine, October 2005.
The basic job of a fire door is to hold back a fire, typically for 30 minutes, and, in some cases, to delay the spread of smoke. For those people unfortunate enough to be involved in a fire, those 30 minutes can accurately be described as the best of their lives, as they increase enormously their chances of survival.
For that vital 30-minute period, the fire doors protect escape routes, giving the occupants of a building an opportunity to exit safely, whilst also providing time for fire fighters to rescue occupants who cannot escape.
Essentially, fire doors work by burning at a slow, controlled rate. Designing a door with the appropriate combustion characteristics is not trivial, and strict standards apply to ensure that doors meet their claimed level of performance. For doors used in the UK, these standards are BS476 Parts 22, 23 and 31 or European Standard BSEN 1634-1.
Ensuring that doors have been tested in line with these standards is a vital step toward an effective fire door installation. It is essential to understand, however, that the tests prescribed by the standards are never carried out on a door left in isolation. They are always performed on complete door sets, which include the frame, hinges and other essential ironmongery.
This is important, as the performance of a fire door installation is only as good as its weakest component. It is not satisfactory, for example, to use doorframes fabricated from materials which happen to be available on site when the door is being fitted. If this is done, there is a very real probability that, in the event of a fire, the frame will fail long before the door, and allow the flames to spread.
Similar considerations apply to hinges and other door fixtures. Cheap general-purpose components may look satisfactory, but could fail to keep the door in position and closed, when subjected to the intense heat of a fire. The preferred solution is to buy complete door sets from a single supplier or, at the very least, to buy only products which have been designed specifically for use with fire doors.
Door seals also need to be carefully considered, since the gap between the frame and the leaf is the most likely area of failure in a fire door installation. In addition, BS5588, which covers fire precautions in the design, construction and use of buildings, requires that doors protecting stairways and escape passages must not only delay the progress of a fire, but also provide a smoke seal.
Protection against gap-related failures and effective smoke sealing is best achieved with intumescent seals. These look similar to ordinary draught seals but, when they are subjected to high temperatures, they swell and completely fill the gap between the door leaf and the frame. The best of the modern intumescent seals swell very rapidly, providing effective protection. They are unaffected by environmental conditions, and are resistant to both general wear and tear, and vandalism.
Of course, no fire door is of value if it is open during the fire. For this reason, all fire doors are required to be fitted with automatic closing mechanisms. Note that simply fitting a spring is not satisfactory – a correctly designed closer must always be used. There is, however, a slight complication. Fire door control products are covered by BSEN 1154 which specifies a minimum closing force of 18N. However, to ensure that persons with mobility disabilities are able to open self-closing doors, the Building Regulations specify that the opening force at the leading edge of the door must not exceed 20N.
It is unlikely that any mechanical door closer will satisfy both of these requirements simultaneously. The solution is to use electromagnetic door controls, such as the hold-open-and-swing-free devices.
Having specified the appropriate doors, frames and hardware, the next hurdle is to ensure that they are correctly installed. For example, it may seem obvious that cutting an aperture in the door and adding a window is likely to adversely affect its fire protection properties, unless the work is carried out by an expert and is approved by the door supplier. Unfortunately, it is by no means unknown for ordinary contractors, who do not have the relevant expertise and experience, to make modifications of this type.
The solution, once again, is straightforward. Use only approved contractors to carry out fire door installations, and ensure that any significant modifications to the basic design are cleared with the supplier of the doors.
Finally, let's cover what is, perhaps, one of the most contentious issues in relation to fire doors: if they're wedged open, they’re never going to provide any protection. Ensuring that the doors are used properly is, to some extent, a matter of discipline and training. However, fitting convenient door controls is an important aid to ensuring correct usage, as is ensuring that signage identifying the door's function is prominent and clear.