Lawrence Webster Forrest (LWF), Fire Engineering and Fire Risk Management Consultants
Lawrence Webster Forrest (LWF), Fire Engineering and Fire Risk Management Consultants


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Lawrence Webster Forrest
Legion House
Lower Road

Tel: +44 (0)20 8668 8663 Fax: +44 (0)20 8668 8583

Unwanted Fire Signals

Unwanted Fire Signals is the formal term given to what has been universally referred to as 'false alarms'.  Unwanted fire signals is considered to encompass the issue and this will become apparent as we expand on this issue.

The majority of building users do not appreciate the local impact of unwanted fire signals or the wider impact.  It is considered that there are two fundamental problems arising from unwanted signals, namely:

·        Desensitisation of fire alarms within buildings

·        Diverting essential resources away from emergency services

It is important that we expand on these issues.  With regards to desensitising fire alarms, this is very apparent in some buildings whereby common faults on the fire alarm mean the evacuation signal is frequently given, consequently occupants, on hearing the fire alarm immediately assume the alarm to be false.  Whilst on the majority of occasions, this may well be the case, the behaviour of occupants, in terms of escape time is likely to have a negative effect, with extreme cases leading to occupants opting not to evacuate at all.  It is clear that this behaviour is unacceptable in terms of fire safety, but it is also understood that this is a learned response which needs addressing.

With regards to diverting emergency services, this is fairly self explanatory if the local Fire Service attend fire alarm activations within the building, which in itself will be dependant on a number of factors, including your geographic location (which Fire Authority you fall under), the building occupancy as well as the type of fire alarm you have and whether it is monitored, building operators should always strive to ensure that emergency services are called in emergencies only, in the current climate, where increasing pressure is placed on resources, this is paramount.

There are a number of secondary (non fire safety issues) that will be of significance to building occupiers also and these will often be the key drivers for change, particularly where there is a commercial impact.  The main issue is business disruption.  This often increases with the size of the building, due to the number of occupants that require evacuating, although other factors, such as the building occupancy / use will have a significant impact, for example, evacuation of a theatre or cinema would be extremely disruptive and would be likely to have commercial implications.

On the basis of the above, it is clear to see the importance of ensuring a fire alarm activates in a 'real' condition only.  We must now consider how to ensure that is the case.

Ideally, the fire alarm system has been appropriately designed and installed with appropriate maintenance in place.  This must be the first objective.  In existing buildings, it is likely that building management will be able to have an influence over the maintenance aspect only, this is however an important function, lack on system maintenance is a common reported fault.

Reporting.  This is a simple identification technique to identify problem areas.  For example, if false alarms frequently occur on the 3rd floor between 9am and 9:30am, this will give a strong indication of what activity is causing the unwanted signal.  Once this has been identified, action can be taken, this could range from prohibiting the activity to changing the local detector heads (following specialist advice).

Delayed evacuation signal - in some instances, this will be appropriate.  This method is commonly used within numerous buildings and when adopted appropriately is advantageous.  Effectively, the fire alarm system can be reconfigured so that multiple sensors are required to activate prior to the fire alarm sounding.  It must however be noted that this effectively reduces the sensitivity of the fire alarm and requires careful and specialist consideration, an enhanced level of fire detection and building management may also be required.  It must also be noted that activation of manual call points would normally initiate an immediate evacuation signal.  Also, this system allows a pre-determined delay period, allowing building management time to investigate the initial activation, if no further information is provided, i.e. 'the all clear' is not given within the time, the alarm will sound.

A very simple but effective tool is a fire risk assessment.  The assessment should take account of the fire risks presents set against the fire detection present.  The risk assessment should also review any unwanted fire signals and be able to ascertain the reason for false activation.  It is likely that the risk assessment will recommend simple, but effective measures, such as replacement of faulty sensor heads / alteration of detector type, for example, changing a smoke detector to a heat detector.

It is clear from the discussion above that the reduction of false alarms is fundamental.  It is also noted that there are some very simple but effective measures that can be implemented to ensure that life safety is achieved, with no unnecessary disruption to building users and without placing a burden on the emergency services.

If you would like to know more – or would like to arrange an appointment with one of our senior fire safety advisers – simply call Peter Gyere on 020 8668 8663.


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