World Patents Pending ©AirSense Technology Ltd. 1999
ISSUE 2.4
Page 10
T E C H N I C A L
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M A N U A L
placed, for example in an air extraction system or within smoke strata which may be
anticipated.
.
A high sensitivity aspirating detector can cover the same volume as many point
detectors, but with added advantages. Economically speaking this allows more money
for the cost of the detector, which, in turn allows it to be designed to be considerably
more sensitive, but with the added advantages of being considerably more stable. The
removal of stringent economic factors also allow a higher degree of repeatability in
performance with a similar reliability to a great quantity of point detectors.
The added advantages of an aspirating system make it the natural choice where very
reliable performance is required. The ability to use a very sensitive system is an
advantage for protecting very clean environments such as computer rooms or micro-
electronics or pharmaceutical manufacturing clean rooms. The air sampling inlets can
be very nearly invisible which makes them ideal for use in historic buildings, where point
smoke detectors would detract from the appeal of the building. Other important
applications are found where their specific properties include; museums, art galleries,
warehouses, telephone exchanges, penal establishments, dusty or dirty areas, unusually
hot or cold areas, areas with high levels of radio energy, atrium buildings, etc.,
The detectors used in successful aspirating systems in recent times, have nearly all been
designed to work on the optical, light scattering principle. There is still one produced
in the UK that uses an Ionisation chamber and another is available from USA that uses
a variant of the Optical principle called a Wilson Cloud Chamber.
The improvements in sensitivity make the optical detector capable of detecting invisible
quantities of smoke. One of the advantages of their very high sensitivity is that indication
occurs so early that it is of a
potential
rather than an
actual
fire. This allows corrective
action to be taken long before an extinguishing action is needed, or indeed, could be
effective. This fact alone translates into savings in the cost of extinguishing agents and
the possible damage its discharge could incur. Also, some of the most common
extinguishing agents are Halons (halogenated hydrocarbons). The manufacture of
these materials is being curtailed because of its damaging effect on the Earth’s ozone
layer.
