False
Fire Alarms: Five Lessons to Learn
Successful fire
detection has helped to reduce the number of fire deaths. But
fire detection and alarm systems (FDAS) are also responsible for a large
number of false alarms – 293,100 were recorded in 2011/12 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.
1. Smoke detectors and
age of components
Optical smoke
detectors were responsible for 74% of the live false alarms observed during study.
The majority of
these were due to cooking, dust, aerosol and steam. 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.
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.
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 signaling 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.
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. 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.