Chapter 2: Installation and assembly
LaserSense HSSD-2 Aspirating Smoke Detector Installers Handbook 17
System design
Aspirating system design is inherently simple. It is often possible to achieve good
system performance with very simple installations. There are however a few
rules which must be adhered to, and these rules are equally applicable to all
aspirating systems which operate on similar principles to this detector. The
information contained in this handbook is intended as an overview only.
Do not expect one detector to achieve good performance if sampling from areas
of different air pressure (typically: under floor air plenums and room spaces or
different rooms in air-conditioned areas). This is because the air pressure
differences may cause reverse or poor airflow along the sampling pipes. If it is
not possible to locate the detector within the protected area it may be necessary
to lead an exhaust pipe from the detector exhaust port returning air to the
protected area. See Figure 11 on page 18.
Always locate the sampling points in a position to which smoke may reasonably
be expected to travel. This may sound obvious, but, for example, do not expect
ceiling mounted sampling points to operate satisfactorily if air flow prevents the
cool smoke from an incipient fire from reaching ceiling level. In this instance it is
usually better to locate the sampling pipes directly in the airflow (for example in
an air conditioning unit air intake). There is no substitute for carrying out smoke
tests prior to installation of pipes to indicate suitable sampling point location.
Note: PipeCAD pipe modeling software must be used when designing a pipe
network and verifying its performance. Refer to the PipeCAD System Design and
Installation User Manual or complete instructions on how to design and install an
air sampling pipe network.
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