Page 18 of 97
Title FireVu Detector Standalone Installation Manual
NetVu Ltd.
No 1 Thellow Heath Park, Northwich Road, Northwich, Cheshire. CW9 6JB
Therefore, in the diagram above, if we assumed a 3.5mm lens, a fire could be 20 metres away (x)
and still result in an alarm as long as “z” were 1% or greater of the detectors vertical field of view
for flame, or 10% or greater of the detectors vertical field of view for smoke.
Height
The ideal scenario with VSD is to have the detector positioned such that if the view were split
horizontally into two equal parts, all “traffic” would pass through only the lower half and the upper
half would be sterile. Traffic refers to anything which may move through the field of view and is
not always present, e.g. people, vehicles or machinery.
In an office space where the only traffic will be people the detector should be positioned between
2 and 3 metres from floor level, although this may be affected by the ceiling height. In larger, taller
spaces the detectors can be positioned higher. The actual mounting height will depend on the
expected traffic height and that of the building itself.
Care must be taken not to mount the detector too high, resulting in a need to point it downwards.
“Not angling the detector down” is more important than “avoiding all movement”. The FireVu
algorithms “see” smoke rising and moving through the image. Consequently, the system will b
e
less effective if looking down upon smoke rising towards the detector, as the movement appears
differently.
Angle of Detector
In order to achieve the criteria required to effectively split the detector view into a lower and upper
half horizontally and any traffic moving through the scene be confined to the lower half, the
detector must be looking out horizontally, otherwise traffic at a distance from the detector will
cross the split and enter the upper half of the view.
The VSD system works by “seeing” smoke rise through the view, it does not detect smoke if it is
rising up towards the detector or if the detector is looking down on the smoke. Consequently, if
the detector is positioned at an angle of greater than 20 degrees it cannot be guaranteed to
“see”
smoke.
Ensuring maximum useable view
Example: In the view to the left, the detector
has been positioned beside a pillar which
effectively makes that area of the view
useless.
