The LWF Blog

Facilities Management – Voice Alarm Systems – Part 4

December 1, 2016 10:06 am

In this blog series for those who work in Facilities Management, we have been looking recently at fire alarm systems and in the last few editions, voice alarm systems in particular. Voice alarm provision can be a most useful addition to a fire alarm system and we have discussed in previous blogs how a voice announcement can have more of an immediate effect on the building occupants than a traditional siren.


Design codes of practice have developed over the years to cover the use of such systems and in this blog, we will look at the factors which must be taken into consideration in the design of a voice alarm system.


While traditional fire alarm design requirements must be taken into account in the design of any fire alarm system, including a voice alarm system, there are some areas which are unique to a voice alarm system and must be considered at the beginning of the design process.


– It should be decided where the responsibility for the overall combined voice and fire detection system will lie. The potential for important considerations or actions to ‘fall through the cracks’ must be minimised.


– The type of interconnections between the fire detection system and voice element must be decided upon based upon requirements.


– The nature of the voice alarm system and a full understanding of how it will be used within the premises is necessary. Will it be used for other emergency situations, such as bomb threats? Might it be used as a public address system, for paging staff, for playing music?


– The applications to which the voice system is to be put must be prioritised, for example, a fire evacuation warning must override all other uses and cancel them out for the duration.


– The acoustic design must be considered and it may be that specialist consultants are required. Additionally, the acoustics of the building must also be taken into account. Reverberation and background noise can substantially reduce the clarity of a PA system. Ambient noise compensation may be required, so as to ensure that the speaker output is always higher than the level of background noise.


– A carefully considered loudspeaker circuit fault method should be designed and implemented. This may be more complex than conventional sounder circuit monitoring.


– The requirement for emergency microphones including how many and the placement of such.


– Interfacing with other sound systems as required must be taken into account and the design adapted to ensure workability.


BS 5839:8 covers all aspects of voice alarm design and the requirements should be followed when designing such a system.


There are many more considerations which must be taken into account in the design of a voice alarm system, over and above those which should be reviewed for a more standard fire alarm system, but it is important that the requirements of both aspects are examined in detail before a final design is put into place.


In next week’s blog, we will look in some detail at the use of voice alarms for other purposes, as well as the practical implications of voice alarm systems in day to day use. 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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