Feature Fire Safety Addressing the problem of false alarms


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


Left: the Chief Fire Officers’


Association is pressing for measures that could mean a reduced level of response for businesses that have a poor unwanted alarm history


A


ccording 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 with- out 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 surpris- ingly, 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


28


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 con- sidered. 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 fea- tures 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 differ- ent 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 counter- act any contamination within the


Below: a fire detection system will only be effective when maintained by a competent person. Poor maintenance will not only lead to unwanted alarms, it may also result in a genuine fire alarm being ignored or missed


sensor chamber, resulting in a consis- tent sensitivity threshold and increased longevity. However, even with these drift compensation algo- rithms employed, eventually the phys- ical 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 guar- antee 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 www.hochikieurope.com T: 01634 266 569


Enter 219 SEPTEMBER 2012 Electrical Engineering


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56