Fire detection systems

Recently I learned about an early warning fire-detection system that is
called an "air sampling system," and wonder if anyone else has looked
into this.  It apparently detects molecules generated during the
pre-combustion stage of a smoldering fire.  The system I looked at was
called VESDA, and I believe there is another brand called Hartnell.

According to the sales representative, the technology was developed in
Australia and has been available in the U.S. only about five years. When
the air sampling system is in operation, air is drawn into an air
sampling pipe network, made of PVC pipe with holes in it.  There is a
filter that screens out large airborn dust particles, and the particles
remaining in the air are examined in a central detector chamber.  The
detector uses a zenon or laser light source and a series of optical
components to examine the way the light is scattered by particles in the
air stream.  A receiver then converts the light to an analog electrical
signal.

I am told that this type of system can detect the presence of smoke
particles up to two hours ahead of a standard smoke detector. Although
the unit is somewhat expensive (a couple thousand dollars) and there is
a cost to installing the piping, it seems more efficient than multiple
smoke detectors.  You only need one in a relatively large space.  I am
curious to know the opinions of those who have installed or looked into
installing such a system, and comments.  With the demise of Halon, it
seems to me that such a system might provide desirable way of creating a
highly-protective environment.

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                  Conservation DistList Instance 8:64
                Distributed: Thursday, February 16, 1995
                        Message Id: cdl-8-64-008
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