June 22, 2016

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False Fire Alarms: Five Lessons to Learn from BRE Study

Successful fire detection has helped to reduce the number of fire deaths in the UK dramatically since the 1980s.

But fire detection and alarm systems (FDAS) are also responsible for a large number of false alarms – 293,100 were recorded in 2013/14 alone.

Estimated losses of around £1bn a year have been attributed to false alarms, due largely to the disruption and loss of productivity in businesses.

False alarms also reduce the confidence of the general public in FDAS. At FIREX 2016, fire alarm expert Raman Chagger shared key findings of BRE’s live study into false alarms conducted in 2014/15 in Glasgow.

1. Smoke detectors and age of components

Optical smoke detectors were responsible for 74% of the live false alarms observed during Chagger’s study.

“The majority of these were due to cooking, dust, aerosol and steam,” Chagger says. “Although 74% may seem high, this type of detector is probably the most common type installed in the field.

“Stringent false alarm tests may be necessary to force manufacturers to develop more sophisticated smoke detectors with greater immunity to false alarms.”

2. Manual call points (MCPs)

False alarms generated from the misuse or accidental operation of manual call points have been observed during a previous BRE study. It was found then that the use of protective covers could reduce false alarms by up to 17%.

False alarms resulted from physical impacts to the sides of the MCP, and other accidental activations as well as malicious (or even ‘good faith’) intent.

Here, false alarms could be reduced by installing covers that require a dual action: lifting the protective cover has to be followed by activating the MCP mechanism; devices with this design have already produced results for the Buckinghamshire and Milton Keynes Fire Authority.

3. Sprinkler flow activation switches

“A drop in water pressure from an activated sprinkler system can cause a signal to be sent to the fire alarm system,” Chagger says.

“These signals can be sent erroneously from sprinkler systems during servicing or when local changes occur, such as a drop in pressure in the water mains.”

Due to the complexity of fire sprinkler systems, more research has to be done before detailed recommendations for reducing false alarms in this area can be made. However, the use of a suitable signalling time delay may in some cases be effective.

4. Procedures dealing with false alarms

Where there were procedures for dealing with fire alarm activations, in 88% of cases they did not address false alarms, and in 93% of cases fire alarm contractors had given no false alarm advice.

“Clearly, this demonstrates a need for more training for the people responsible for writing procedures, and for a greater exchange of false alarm information,” Chagger remarks.

Further research work could be used to provide valuable guidance on how to reduce false alarms to a much wider audience. Frequent meetings between stakeholders are recommended to support this.

5. Multi-sensor detectors

“None of the false alarm observed came from multi-sensors,” Chagger says. “Backed by anecdotal accounts, this finding is encouraging and suggests that multi-sensors do not cause many false alarms.”

However, the BRE alarm specialist cautions, that there are many different types of devices, each with their own false alarm rejection criteria, which could produce a broad range of alarm responses.

Some multi-sensor detectors may be set up to respond to one fire phenomenon only (e.g. steam). This would mean that, though less prone to producing false alarms, they may also be less sensitive to detecting certain types of smoke.

Further research is required to support the use of multi-sensor detectors. The findings should then be used to inform codes of practice and building regulations.

Raman Chagger is a Principal Consultant, Fire Detection for BRE. His full study into false alarms can be found here.

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