Causes of UwFS and How to Reduce Them

There are a number of common causes of unwanted fire signals. The table below offers advice and solutions on how to reduce them.



Cooking fumes

Ensure that cooking is only permitted in designated locations which have appropriate detection (usually heat). Correct use of extractor fans and the closing of doors between designated cooking areas and detector heads can further prevent false alarms.

Burnt toast

Do not leave toast unattended and, if required, close doors and open windows to prevent actuation of a detector.  The use of toasters could be restricted to designated areas.

Steam (i.e. from shower rooms)

Ensure there is adequate ventilation in the shower room and keep doors to outer rooms closed. Sometimes signage can help guests/staff understand the need to close doors and take action to avoid build-up of excessive steam.


Smoking should only be allowed in designated locations protected by appropriate detectors, i.e. which are designed to be suitable for the risk whilst not being susceptible to actuation from cigarette smoke.

Aerosol sprays

Where possible, you should prevent the use of aerosols in the vicinity of fire alarm detector heads. If this cannot be avoided, use of alternative products should be considered.

Contractors working onsite

Contractors should be fully briefed on your fire safety arrangements, the location of fire detection systems, and the emergency plan applicable to their working location. Ensure that proper procedures are in place to control the nature of any work (e.g. hot-work permits) and ensure that you and your contractors clearly identify the areas in which the work can take place.  Temporary covers could be fitted to detectors in the area, or the zone isolated from the fire alarm system during the work period and control measures introduced.  These measures should be removed immediately after the activity has ended. Whilst detectors are covered in this way, staff working in the area (including contractors) should be briefed to activate a 'break glass' call point if they see a fire.

Accidental or malicious actuation of a 'break glass' call point

Consider protecting susceptible break glass call points with approved covers or guards and additional signage.  If required, consider the use of CCTV.

Testing or maintenance

Prior to commencing any testing or maintenance you must instruct your alarm centre to take your system 'off watch' for the duration of the activity.

Changes to the use, or practices within the building

Ensure the fire-detection system is appropriate for how the building is used.  Your risk assessment will need to be updated to reflect the changes.

If these actuations continue to occur despite suitable management procedures being put in place, then it may be beneficial to contact your fire alarm engineer.  They will be able to consider alternatives, such as:

  • The location and type of detectors could be assessed and altered (including sensitivity settings) where necessary to reduce the number of UwFS but still provide suitable and appropriate protection.
  • The use of an investigation period being afforded by the alarm system before the alarm signal is sent to the alarm receiving centre (ARC) will allow for a suitable investigation and, if it is found to be a false alarm, the system can be reset before the signal is sent to the ARC.
  • The implementation of a coincidence detection system. This is where two detecting devices need to be activated before an alarm signal is sent to an ARC (this can be overridden by the operation of a manual call point or a heat-activated device, such as a heat detector or a sprinkler system).
  • In certain premises the alarm system could be taken ‘off line’ during the day when the sleeping risk is reduced and there are enough staff to manage a fire alarm actuation (including a robust system for summoning the fire service when required).

In all cases a risk assessment will need to be undertaken to ensure the safety of relevant persons. It is important to note that only competent or qualified persons should operate your fire alarm system, in accordance with BS 5839.