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Sampling Pipe Design
Above ceiling sampling with exposed detector
Simple designs with short sampling pipes produce the best results. Complex sampling pipe runs should be
avoided with the FastSense 25 detector. The use of ‘T’ branch
-pipes is not recommended. Always locate the
sampling points in positions to which smoke may reasonably be expected to travel. Do not expect ceiling
mounted sampling points to operate satisfactorily if air flow from air-conditioning systems keeps the cool
smoke from an incipient fire reaching from reaching ceiling level. In this instance it is usually better to locate the
sampling pipe directly in the airflow (for example across the return air register of an air conditioning unit).
There is no substitute for carrying out smoke tests prior to installation of pipe work to indicate suitable
sampling point location.
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. The information contained
in this Handbook is intended as an overview only. For further information please see the complete System
Design Guide.
Do not expect one detector to achieve good performance if sampling from areas of different air pressure
(typically: underfloor 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 pipe. 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.
The piped exhaust docking station needs to be used in this case.
FastSense 25
Exhaust Pipe
False Ceiling
Sampling Pipe
Sampling Hole
