As Stuart Davies of Hochiki Europe explains, the cost of poor false and unwanted alarm management to the UK (which is estimated at around £1bn a year), can be significantly reduced with the correct specification, installation and maintenance of fire detection equipment
According to statistics published by the Department for Communities & Local Government, around half of the 727,000 attendances to premises by fire and rescue services in 2008 were due to false or unwanted alarms. Wind forward four years and fire crews are still finding themselves being called out as a consequence of alarms being triggered by burning toast, steam from showers or contractors operating without a permit to work.
This is clearly a major issue for fire services in terms of time and resources – indeed, there could soon be measures introduced that will see a reduced level of response for businesses that have a poor unwanted alarm history.
Fire and rescue services are now requesting that offices and factories check there is a genuine blaze before dialling 999 and although this is reducing the number of unnecessary call outs, it is not enough. Not surprisingly, there is mounting support for those that routinely raise false alarms to be served with an improvement notice that, if breached, will result in court action.
Reason being
There are several reasons for unwanted alarms such as poor product selection, misguided installation, the activities of people or processes within the building, or inadequate system maintenance. The first of these can be eliminated with a risk assessment to identify likely fire risks. The correct products can then be matched to the specific requirements of the premises.
The selection and siting of these products must then be carefully considered. For example, manual call points should not be positioned where malicious damage can occur and with automatic smoke detectors generating more unwanted alarms than any other type of device, they must be located in the most suitable area possible. Equally, when an area changes its use, the type of fire detector sited there must be reviewed.
Some products include built-in features to reduce unwanted alarms. For instance, optical chamber technology has been developed that minimises the differences in sensitivity experienced in flaming and smouldering fires, resulting in a chamber that is equally responsive to all smoke types.
Variable sensitivity products can be controlled via a time clock or an event such as a security alarm being set or unset – taking into account the different occupancy levels during a period of time i.e. reducing the sensitivity of the detector during the occupied period can have a significant impact on false alarms in some premises.
Drift compensation
Products are also available that have a compensation feature against dust or dirt build-up. They automatically adjust the alarm threshold to counteract any contamination within the sensor chamber, resulting in a consistent sensitivity threshold and increased longevity. However, even with these drift compensation algorithms employed, eventually the physical removal of dust will become necessary so a good maintenance regime will ensure this happens at the appropriate time.
Some detector designs make it easy to dismantle the detector, remove the chamber and clean or replace it on-site. However, this should only be done when the manufacturer can guarantee that once the detector has been reassembled it will automatically recalibrate itself. Calibration in this way ensures that the sensitivity of the sensor is the same from the day it was installed until the contamination is beyond compensation, at which point it should be serviced again.
The effectiveness of a fire detection system is dependant on maintenance from a competent person, and an unwanted alarm may not be the only consequence of poor maintenance as it may also lead to a genuine fire alarm being ignored or missed.
Guidance on maintaining a system, together with advice on reducing unwanted alarms, can be found in BS 5839 Part 1. This Code of Practice accepts that the complete elimination of unwanted alarms is not possible, however, it does recommend that at each service the number of false or unwanted alarms during the previous year be recorded. If the total goes above a certain threshold, measures should be taken to address the issue. Responsible fire detection system manufacturers are also able to offer a wide range of information and advice on this subject.
Hochiki Europe
T: 01634 266 569
