Product guide

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14
DISCOVERY CARBON MONOXIDE DETECTOR
Discovery Carbon Monoxide Detector ▲ Part Number 58000-300
OPERATING
PRINCIPLES
Discovery CO fire detectors
contain a long-life electro-
chemical carbon monoxide
sensor which is tolerant of
low levels of common
vapours and household
products. The sensing
technology is fast, accurate
and needs only very low
power. These factors make
the CO sensor suitable for
fire detection applications.
The detection capabilities
are enhanced by a rate-
sensitive response. Fast rises
in the carbon monoxide
level are often associated
with hot fires and the
detector will respond earlier
under these conditions. The
analogue reply from the
detector is rate limited to
remove nuisance alarms
resulting from short-term
high levels caused by
sources such as pipe
smokers or gas flame
ignition.
APPLICATION
CO detectors do not detect
smoke particles or heat and
are not universal
replacements for smoke
detectors.
Apollo does not endorse the
use of CO detectors as the
main method of fire
detection if:
■ the protected area is an
escape route
■ there is a requirement to
detect overheating of
electrical equipment or
cables
■ the protected area is
exposed to sources of CO
such as vehicle exhausts,
or to hydrogen or to high
levels of alcohol vapour
as emitted by some
cleaning agents
■ there is a requirement to
detect fires involving
flammable liquids
CO fire detectors are
particularly suitable for
supplementing smoke
detection when there is:
■ a deep seated
smouldering fire risk
■ a risk of fire starting in an
enclosed space
■ a likelihood of
stratification taking place
Carbon monoxide detectors
may be used as the primary
fire detector in areas where
the following conditions
exist:
■ the main risk is
smouldering fires
■ optical smoke detectors
are deemed unsuitable
(see ‘FALSE ALARMS’
below)
■ the fire compartment is
not greater than 50m
2
Typical applications include
hotel bedrooms, halls of
residence, sheltered
accommodation and
hospital wards.
DETECTOR SITING
CO fire detectors should
be sited using the
recommendations for smoke
detectors from BS5839: Part
1 (or other applicable code).
In the development of a fire,
smoke and CO in the
smoke plume is spread by
convection to a fire detector.
As CO is a gas, it further
spreads—like smells—by
diffusion. For this reason
CO may reach a detector
faster than smoke would.
This potential advantage
can be exploited when
designing a fire protection
system and CO detectors
may be used for
supplementary detection.
Equally, the opposite effect
might occur, with CO
moving away from a
detector.
The behaviour of CO is
therefore unpredictable and
diffusion should not be
relied on when designing a
fire protection system.
FALSE ALARMS
Carbon monoxide detectors
are less susceptible than
smoke detectors to false
alarms from sources such as
toast, steam, cooking,
plumbing work and hair
spray. They may therefore
be used in some
applications in which
smoke detectors would be
susceptible to unwanted
alarms.
Conversely, they may be
more susceptible than
smoke detectors to false
alarms from fumes
containing CO, such as
vehicle exhausts, open fires
and gas appliances.