The LWF Blog

Fire Safety for Facilities Management Personnel – Fire Detection & Fire Alarms – Part 204

June 5, 2023 10:48 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 203, LWF discussed false alarms, in terms of how many false alarms can be considered ‘acceptable’. In part 204, we talk about the proper maintenance and servicing of fire alarm systems, in the light of limiting false alarms.

The regular and adequate servicing of a fire alarm system can help to improve the rate of false alarms. BS 5839-1 recommends that an investigation is carried out during servicing if any of the following statements are relevant:

  • That the rate of false alarms in the 12 months prior to service (or any 12 month period) has exceeded one false alarm per 25 detectors
  • If 11 or more false alarms have occurred since the last service visit
  • Where two or more false alarms have arisen from a single manual call point or detector
  • In situations where any persistent cause of false alarms is identified

It is possible that in certain circumstances, even if the above conditions are not met, false fire alarm signals can prove to be more than a nuisance. In a large building with a correspondingly large fire alarm system, one false alarm per 100 detectors might mean a rate of one false alarm signal per week in a system with 5000 detectors.

Such issues are often remedied by the implementation of a staff alarm system, where when a signal is received from a single detector at the fire alarm control and indicating equipment (CIE), pagers held by staff members or other devices are triggered to alert nominated staff members so that they may investigate more fully. In these cases, a full alarm signal is not issued in any area of the building until confirmation has been received, either by the investigating staff member or a second detector signal received at the CIE. The Fire Service are not typically summoned until confirmation is received.

Such systems are set with a time delay function to enable investigation. They work to allow a small period of time for investigation and feedback, after which, if no cancellation is received, a general alarm for evacuation is commenced.

Usually, a full alarm is given if a manual call point is activated, or where two detectors are operated during the investigation period.

In part 205 of this series, LWF will discuss the summoning of the Fire Service by the fire alarm system for property protection. 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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