The LWF Blog

Fire Engineering Design and Risk Assessment – Fire Alarm Control Equipment – Part 20

October 12, 2016 11:26 am

In our recent fire safety blog series for Architects and those people who work in designing and building properties, we have been looking at the importance of understanding different types of fire alarm system and the composite parts.  Today, we look at the control equipment – the brains of a fire alarm system.


The Control and Indicating Equipment (referred to as CIE) is the part of a fire alarm system from which the user can identify the location of a fire, look at indicated faults and control the operation of the alarm sounders, detectors etc. The CIE must comply with BS 5839:4 in the UK or appropriate equivalent in other countries.


The siting of the equipment is important, both in terms of appropriate accessibility and security. The CIE should be accessible by and visible to appropriate staff on duty, as well as being near the entrance to the property (on the ground floor where possible) so as to enable Fire Service representatives use upon arrival.


Close to the CIE, a chart or diagram which shows zone designation should be displayed, so that a zone code given by the control equipment can be translated easily into an actual location within the building.


Another significant part of the fire alarm system is the sounders, which are used when an alarm signal is received by the CIE. The sounder normally takes the form of a ringing bell or an electronic siren which is audible throughout the whole building. A building that has been subject to a fire engineered fire prevention solution may have a voice sounder instead of a general alarm bell. The voice alarm may give a simple instruction to those occupants of the building hearing it.


BS5839:1 provides guidance in the UK on the correct purposing and use of alarm sounders. It states that an alarm sounder must produce a sound level of 65dBA, or 5dBA above the level of any background noise which is likely to persist for longer than 30 seconds – whichever is greater.


Doors and walls both reduce the sound level significantly as sound passes through them, this can be as much as 20dBA for a normal door and 30dBA for a fire door. At the time of installation of the system, sound levels must be checked in all areas and in those which drop below the minimum sound level of 65dBA, additional sounders should be installed to increase the sound level. Slight variations of around 2/3dBA in a small area could be acceptable.


In next week’s blog, we’ll continue to look at the guidance of BS5839:1 in relation to alarm sounders. In the meantime, if you have any questions about this blog, or wish to discuss your own project with one of our fire engineers, please contact us.


Lawrence Webster Forrest has been working with their clients for over 25 years to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact Peter Gyere on 020 8668 8663.


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