The LWF Blog

Fire Safety for Facilities Management Personnel – Fire Detection & Fire Alarms – Part 202

May 22, 2023 11:40 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 201, LWF discussed analogue addressable fire alarm systems. In part 202, we begin to look at the reasons for and impact of false fire alarms.

False alarms are a significant problem, often associated with having an ill-performing or badly calibrated fire alarm system. A fire alarm system which often gives false alarms has a detrimental effect on the building occupants’ response time to an alarm. Repeated exposure to false fire alarm signals mean that the hearer will assume it is a false alarm upon hearing it, rather than assuming the alarm is sounded due to a fire.

Additionally, false alarms are an issue for the Fire Service. A significant number of calls to the Fire Service are as the result of a false alarm.

Many false alarms can be classed as ‘unwanted alarms’, meaning that the system worked as intended but responded to the smoke from an outside bonfire entering the building, or to steam from an industrial process or bathroom, or similar.

Newer fire alarm systems, particularly analogue types, should help in providing fewer false alarms.

Some common causes of smoke alarms are:

  • Cooking process fumes, including making toast, flambéing etc.
  • Steam from industrial processes, shower rooms and bathrooms
  • Cigarettes and other smoking materials
  • Dust – may be accumulated or from an industrial process
  • Insects
  • Aerosols – e.g. deodorants and cleaning fluids
  • High air velocities
  • Smoke from other sources (such as the aforementioned bonfire outside)
  • Hot work, e.g. welding and cutting etc.
  • Cosmetic and effects smoke – from theatres or night clubs
  • Incense or candles
  • Electromagnetic interference
  • Humidity (high) or water ingress
  • Temperature fluctuation
  • Accidental damage to manual call points
  • Incorrectly carried out testing and maintenance
  • Pressure surges in the water mains supplying automatic sprinkler systems

While the list is not exhaustive, it can be seen that false fire alarms can be caused by a wide variety of situations and issues, many of which cannot be foreseen or avoided by the building owner.

In part 203 of this series, LWF will continue to discuss false alarms in terms of how many false alarms can be considered ‘acceptable’. 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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