15
MAN3038-2
DISCOVERY PRODUCT GUIDE
9
Carbon Monoxide Detector
9.1
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. 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 50m²
Typical applications include hotel bedrooms, halls of residence, sheltered accommodation and hospital
wards.
Detector Sitting
CO fire detectors should be sited using the recommendations 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.
