The LWF Blog
Facilities Management – Voice Alarm Systems – Part 7
December 22, 2016 12:44 pmIn this blog series for those who work in Facilities Management and who have a responsibility for fire safety, we have been looking at the differences between standard fire alarm systems and voice fire alarm systems. A voice fire alarm system is one which does not have traditional alarm sounders, but instead delivers a specific message or instruction about evacuating the building when a fire occurs.
While such systems have been proven to be more effective at reducing the time taken for people to begin evacuating, the inclusion of voice alarm sounders does involve certain complications which must be taken into account prior to installation.
In today’s blog we are continuing to look at how voice sound can be distorted by an increase in background noise, through hard surfaces causing reverberation, or when it must pass through an obstacle such as a wall.
It might seem a difficult proposition to design a system which takes into account these sound anomalies in a space, but it is possible to quantify intelligibility with the use of specialist test equipment, except these tests can only be run after installation. It is wise, therefore to specify the required intelligibility level at design stage so that if a dispute arises after installation, it can be proven if it does or doesn’t meet the requirements.
Significant variations in background noise should certainly be a consideration prior to installation of a voice alarm system. A building which is exposed to high levels of noise at some points of the day must have a system which can operate effectively at those times, as well as when it is quiet. Background noise sensors can be installed as a part of a system to vary the output as required.
One such example would be an airport or train station, or indeed, the building in question being situated close to such a place. The trains or planes arriving and leaving can cause a significant increase in background noise above which a voice alarm must be audible in case of fire danger.
Such voice fire alarm systems require regular maintenance as would a standard fire alarm system and so are subject to the statutory requirements for testing and maintenance of a standard system, but in addition, the effective operation of the microphones should be checked weekly and quarterly, all loudspeaker zones must be checked for correct operation.
It is certainly worth mentioning that as the microphones and speakers can be used for other purposes than a fire alarm, that weekly testing of the fire alarm message, which is pre-recorded, is also a must. It is not sufficient to simply use the system to give standard announcements and assume that its continued operation means it will work in a fire situation. Of course, message intelligibility must also be checked in all areas of the building.
In next week’s blog, we will begin looking at fire extinguishing equipment – what there is a need for and how and when it should be used. 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