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MAN3038-2
DISCOVERY PRODUCT GUIDE
16
Maintenance of Detectors
Detectors should be maintained according to BS5839 or other locally applicable code. Test equipment can
be ordered from Ampac for testing smoke and heat detectors. Detectors should not be cleaned in the field
except for careful removal of exterior dirt with a damp cloth. For cleaning and recalibration detectors should
be returned to the manufacturer or to the local distributor.
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Application of Discovery Detectors
The process of designing a fire detection system using Discovery detectors is the same as that used for any
other detector range, except that Discovery offers more choices to the system designer. The principles set
out in relevant codes of practice such as BS5839: Part 1 should be followed in any system design. The notes
below are intended to supplement the codes of practice and to give some specific guidance on the choices
available with the Discovery range.
Choice of Detector Type
The choice of detector from the Discovery range follows the well established principles of system design.
That is, the optimum detector type will depend on the type of fire risk and fire load, and the type of
environment in which the detector is sited.
For general use, smoke detectors are recommended since these give the highest level of protection. Smoke
detectors from the Discovery range may be ionisation, optical or multisensory types. The most widely used
single sensor detector is the optical smoke detector. For the greatest versatility in designing fire detection
systems the optical/heat multisensor is the detector of choice.
Ionisation smoke detectors are excellent at detecting small particle smoke and providing early warning of a
fire but they must be used in an environmentally friendly way.
The optical/heat multisensor is basically an optical smoke detector and will therefore respond well to the
smoke from smouldering fires. In response modes 1, 3 and 4, however, (ie, in the multisensor modes) the
detector also senses air temperature. This temperature sensitivity allows the multisensor to give a response
to fast burning (flaming) fires which is similar to that of an ionisation detector. The multisensor can therefore
be used as an alternative to an ionisation detector while still retaining the benefits of an optical smoke
detector.
Where the environment is smoky or dirty under normal conditions, a heat detector may be more appropriate.
It must be recognised, however, that any heat detector will respond only when the fire is well established and
generating a high heat output. The Discovery heat detector can be used in a wide range of conditions by
selecting the correct mode (see Table 9).
The relative performance of the six detector types for different fire types is given in Table 8.
Choice of Response Mode
A major objective in designing a detection system is to achieve the best detection performance while keeping
the number of unwanted alarms at a low level. Unwanted alarms are normally caused by environmental
influences. For any given environment, unwanted alarms will, as a rule, be more frequent for detectors of
higher sensitivity.
It has already been pointed out that the response modes for Discovery detectors correspond to different
sensitivity to fire, with response mode 1 being more sensitive than mode 5. It follows, then, that Discovery
detectors set to mode 1 will be most suitable for environments in which sources of unwanted alarms are rare.
Such environments include clean rooms and computer suites.
