The LWF Blog

Fire Safety for Facilities Management Personnel – Voice Alarm Systems – Part 213

August 7, 2023 11:03 am

Lawrence Webster Forrest (LWF) is a specialist fire engineering and fire risk management consultancy whose aim is to give information on best practice in fire safety for facilities management personnel through this blog series. In part 212, LWF looked at the design code of practice for voice alarm systems. In part 213, we discuss what factors should be considered in the design of a voice alarm system.

Any fire alarm system requires the consideration of traditional engineering issues that must be taken into account, such as fault monitoring and fire-resistance of the wiring. Voice alarm systems also have additional considerations which require addressing at the beginning of the design and specification period.

The factors specific to voice alarm systems that should be considered, over and above the standard engineering factors, are as follows:

  • Who will take overall responsibility for the combined fire detection and voice alarm system?
  • The type and requirements for interconnections between the fire detection and voice alarm system
  • Will the system be required to broadcast other hazard/safety warnings, such as bomb warnings?
  • Is the system to be used additionally for paging and/or background music/general announcements?
  • How the applications should be prioritised
  • Are specialist consultants required to consider the acoustic design?
  • The acoustic environment of the building, e.g. reverberation time and background noise
  • Fault monitoring of the loudspeaker circuit, which may be more complex than conventional sounder circuit monitoring
  • The potential need for ambient noise sensing and compensation, to ensure that the output sound of the alarm system is always greater than the background noise level
  • The required level of intelligibility
  • The need for and number of emergency microphones
  • Does the system need to interface with other sound systems?

Information on all of the above points can be found in BS 5839-8

A voice alarm system may be used for other purposes than giving warnings of fire in the UK, but in North America, this is not usually permitted. Some of the purposes that the voice alarm system may be used for include giving warnings of other hazards, e.g. bomb threats, and use of the system as a conventional public address system for staff paging, background music etc.

It is vital when the system is used for other purposes that any non-essential uses are overridden and locked out when the system is needed for fire alarm warnings. The primary use must always have priority.

Fiscally, the installation of a voice alarm system can be more expensive than a standard system with alarm sounders, however, when it can be used as a public address system too, the perceived cost/benefit ratio is more acceptable.

In part 214 of this series, LWF will look at emergency microphones and message sources. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact LWF on freephone 0800 410 1130.


Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 35 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.


While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.

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