This high proportion of false alarms has a significant impact on UK local authority fire brigades. False alarms reduce their availability for real fires and are a financial liability. They cost industry in lost production time and affect the safety of building occupants by increasing evacuation time in real fire situations (crying wolf).
The code gives a great deal of attention to minimizing false alarms.
When a false alarm occurs it now has to be recorded, and categorized as one the following:
- Unwanted alarms
- Alarms in which the system has operated as designed
- Has responded as expected to its environment
- Accidental damage
- Action by people.
- Equipment false alarms
- Alarms generated from a fault within the system equipment.
- Malicious false alarms
- Alarms in which someone intentionally triggers a fire alarm knowing that there is no fire.
- False alarms with good intent
- These are alarms in which someone intentionally triggers a fire alarm believing that there is a fire.
- If it is not possible to establish the cause of the false alarm it should be recorded as
Whilst all false alarms are undesirable the code accepts that the complete elimination of false alarms is not possible.
- It recommends that at each annual service the number of false alarms during the previous year be recorded and expressed as the number per 100 detectors.
- Well managed clean environments a rate of 1 false alarm per 100 detectors should be achievable
- Industrial applications a rate of 1 per 75 detectors is more realistic.
An in-depth investigation should take place, followed by appropriate remedial action where the annual rate exceeds:
- 1 per 20 detectors
- More than two false alarms initiated by a single manual call point or automatic fire detection device
In systems with 40 or fewer automatic detectors
- An in-depth investigation should take place if more than 3 false alarms occur in any rolling 12 month period.
In many cases equipment faults are blamed for the false alarms, but the cause is usually:
- Incorrect selection of type of detector
- Siting of detectors.
Common causes of false alarms are:
- Fumes from cooking processes
- Steam from bathrooms and showers
- Tobacco smoke
- Aerosol sprays.
- Building work, The code recommends the following:
‘Tender documents for contract work to be carried out in a protected area should contain a clause making the contractors responsible for informing their staff of the presence of any automatic fire detectors, and of the precautions to be adopted when working’.
Specifications should also require contractors to submit statements identifying methods of working to avoid false alarms.
Temporary measures to prevent false alarms, such as replacing smoke sensors with heat sensors or covering detector heads, should be agreed with the fire authority beforehand.
The code outlines a selection of design measures that can be used to limit false alarms:
- Manual call points should not be positioned where malicious damage can occur. For example, in leisure centres – with the agreement of all interested parties – manual call points could be installed in staff locations but not within public spaces.
- Automatic smoke detectors generate more false alarms than any other type of detector – careful consideration should be given to their selection and siting. The code recommends that smoke detectors should not be installed in kitchens, toilets or where steam occurs during normal operation.
With the advances in electronic technology the fire alarm industry can now provide systems which are more resilient and produce fewer false alarms, their success depends upon designers knowing enough about the building detail and its eventual use to make informed choices. Sophisticated single and multi-sensor detectors are available which use algorithms to filter out temporary abnormal readings which, in the past, would have generated false alarms.
For more information or help to reduce your number of False Alarms contact us on:
01769 575 040