The LWF Blog

Facilities Management – Fire Alarm Systems – Part 21

October 25, 2016 1:55 pm

In this blog series for Facilities Managers and those with an interest in and responsibility for fire safety, we have been looking at fire alarm systems and how they interface with other systems. In our last blog we noted how a fire alarm system can be linked to other systems to enable procedures to be carried out if the fire alarm sounds. This might be returning lifts to ground level or closing ventilation and air-conditioning ducts to avoid the spread of smoke and fire, amongst other things.


While BS 5839-1 gives guidance on the primary function of fire alarm systems, it does not explicitly cover such interfaces and although the other systems involved may be covered by other codes of practice or regulation, the combination of a fire alarm and another functions has historically simply been down to good engineering judgement. However, in the last 30 years, changes to British Standards means that guidance in codes of practice has begun to come into play through parts of BS 7273.


BS 7273-1, for instance, which was last revised in 2006, looks at a fire alarm interface with a total flooding gaseous fire extinguishing system. This means that if you were to interface a fire alarm with a total flooding gaseous fire extinguishing system, you would need to refer to three appropriate guidance documents – BS 5839-1 (for the fire alarm system itself), BS ISO 14520 (for the extinguishing system) and BS 7273-1 for the interface.


BS 7273-2 relates specifically to the interface with a mechanically operated local operation or total flooding gaseous extinguishing system, but such systems are quite rare.


BS 7273-3 looks at the interface with a pre-action sprinkler system.


BS 7273-4 is a much more commonly referenced piece of guidance as it deals with the interface between a fire alarm system and door release units, which is, of course, one of the most common interfaces in use. Door release units is a term which encompasses those fire doors which are held open under normal operation but closed upon operation of the fire alarm system to avoid the spread of fire between compartments. They are operated during a fire situation and will self-close behind the person using it.


These systems are increasingly common as they allow unencumbered access within the building’s corridors to people who may be carrying things or who may have mobility issues, but that when a means of escape situation is established, they are closed correctly to protect the escape route.


This area of the British Standard also covers automatically locking doors interfacing with the fire alarm system. These systems are in increasing use across the board, but most especially in buildings with security issues (banks, hospitals etc. to keep intruders out and in prisons and secure mental health units to keep residents in). It is important that these doors remain secure under normal operation, but that they release immediately upon a fire signal received from the fire alarm system, to allow the escape of the people inside.


It is important therefore, that this operation is covered by a British Standard to avoid situations where the electronic locks do not release at the appropriate time, causing increased danger to those occupants of the building.


Finally, BS 7273-4 covers the use of electronic sliding doors. The doors which usually open when a sensor indicates a person approaches the doors must open fully and remain open in a fire situation.


BS 7273-5 covers recommendations for fire alarm interfacing with water mist suppression systems.


In our next blog we will look at how often fire alarm systems should be checked as part of routine maintenance. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact Peter Gyere in the first instance on 0208 668 8663.


Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 25 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.


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