Fire alarms are a problem, especially as now many fire and rescue services are not responding to unconfirmed alarms from automatic systems. But there are many ways that users can reduce the problem.
False alarms are a problem, because of the disruption to a business and the risk to fire safety. The annual cost in the UK is estimated at ?1 billion, but only 10% of systems cause 80% of false alarms.
The fire alarm industry has always been concerned with minimising false alarm signals because unwanted fire signals are a threat to fire safety. Recurring false alarms could cause people to become complacent and therefore they may not react as they should in the event of a real fire signal. Unwanted alarms may also cause costly disruption and loss of business to both the fire and rescue service, as well as the business concerned.
BS 5839-1 has a whole section devoted to limiting false alarms
A well designed fire alarm installation which uses the appropriate equipment and is managed in a way that matches the building’s use should not suffer from these problems. However, it is important to realise the need for ongoing false alarm management. BS 5839-1, Fire detection and fire detection systems for buildings. Code of practice for system design, installation, commissioning and maintenance, offers guidance and the whole of section 3 is dedicated to the limitation of false alarms.
Part of a false alarm management strategy should be to set target levels of false alarm events – this target should be constantly challenged with the objective of driving them down to zero. It’s advisable to keep a detailed record of each false alarm; taking note of the date, time, identity and location of the trigger device; the category of false alarm; the reason for the false alarm and any activity or events that contributed to the alarm.
To help with record keeping, several categories of false alarm event are defined:
Equipment false alarm: any type of genuine equipment fault
Unwanted alarm: environmental influences, fire-like phenomena, inappropriate action by people in the building and accidental damage
Malicious false alarms: deliberate malicious alarm
False alarms with good intent: alarm is raised by a person with genuine belief that there is a fire
Equipment failure tends to be the least common cause of false alarms as most are due to ‘unwanted alarms’ which, as mentioned above, are caused by fire-like phenomena or inappropriate action by people in the building. All ‘unwanted alarms’ should be investigated to identify the cause and changes implemented to prevent a recurrence of the problem. These can normally be avoided through careful management of the building which includes regular maintenance of the fire alarm system. Any changes in the building’s use, even temporarily, must be assessed to consider whether modifications are required – this includes supervision of any painting/decorating or hot work in the building.
There are many causes of ‘unwanted alarms’ but fire detection and alarm equipment is able to provide a wide range of techniques and measures that will help to manage the problem. The most basic requirement is selecting the correct type of detector and its appropriate positioning when considering the risk and the building’s use. Smoke detectors are, generally, sensitive to airborne particles and inappropriately used they may not discriminate between smoke and other particles such as dust, insects and steam. A wide range of different technologies are available but these need to be matched to the application. It is important that detectors are positioned to avoid steam, cooking fumes or cigarette smoke. Recent developments in multi sensor devices can be particularly effective in the battle against ‘unwanted alarms’.
Perhaps the most obvious method of preventing false alarms is to keep processes that may trigger them away from detectors, manage the process with a ‘permit to work’ system, or simply by improving ventilation. If there is no other option but to cover or disable detectors, such action must always take into account the risk assessment of the building and alternative measures or mitigation should be in place.
Another approach may be to introduce a delay of up to 10 minutes where an initial alert is given to fire marshals, allowing them to investigate and confirm the fire signal. Any delay would immediately be cancelled by operating a manual call point, allowing evacuation of the building and summoning the fire brigade. Of course, the delay system would only operate during the day when people are in the building. Another useful time dependant feature is to reduce detector sensitivity when the building is occupied and false alarms are more likely.
An effective technique suitable in certain applications is to use more than one alarm signal. In this case the fire panel does not go into alarm with the initial fire signal but waits for a second confirmatory signal. The confirmation signal could be from the same detector after a short period of time or a different detector in the same or different zone (but similar physical location). It may be suitable to confirm an initial alarm signal from one type of detector (i.e. a smoke detector) with a second signal from a different technology detector (i.e. a heat detector).
But reducing false alarms is not all about fire detection and alarm system technology. Staff training aimed at avoiding false alarms, while maintaining a culture of safety among the workforce, is also fundamental.
Extract taken from LG Fire Safety Services