Page 16 of 97
Title FireVu Detector Standalone Installation Manual
NetVu Ltd.
No 1 Thellow Heath Park, Northwich Road, Northwich, Cheshire. CW9 6JB
●
Highly polished shiny floors, especially if combined with large openings where shadows and
bright sunlight will cause reflections and large contrast changes.
●
If using flame detection, the presence of flashing beacons or lights on fast moving vehicles
will require a higher threshold setting to avoid false alarms. Consequently, there will be an
increase in the minimum flame size that will be detected.
Environmental Considerations
Adequate lighting is required for the presence of smoke to be defined sufficiently for accurate VSD
operation. Typically, a minimum of 20 lux of visible light is required. This is only required for the
visual smoke detection. Both the visual flame detection and heat detection will work at any
illumination.
Detector Lens Selection
The detection footprints defined further on within this section are based upon the assumption that
for effective smoke detection 10% of the screen height would be occupied by the minimum
amount of smoke that is required to be detected. This applies to the furthest point in the field of
view where the user is intending that the detector in question will monitor and respond as
required.
For practical purposes, a human target occupying 10% screen height at the furthest point is
assumed to be a suitable size to produce good results, meaning that a smoke cloud will need to be
approximately 2m (6 feet) high and 600mm (2 feet) wide at the furthest point within the monitored
area before effective detection will take place. Consequently, a smaller smoke cloud will result in
an alarm if closer to the detector.
Response distance for flame is based upon a need to respond in less than 30 seconds to a 330mm
x 33
0mm x 50mm (13” x13” x 2”) pan fire with 500ml (1.06 US pints) of N Heptane.
Detector Positioning
Detectors should be mounted on as firm a structure as possible. If large amounts of detector
vibration are present, then the video image will have continuing large differences within it and the
detection algorithms will be less effective. FireVu analyses changes within the video images it
receives on a pixel by pixel basis. Consequently, if all pixels and constantly changing as a result of
“camera shake” it
s sensitivity to changes as a result of smoke presence will be reduced.
Covering the “Risk Area”
Note:
Before deciding upon a position for Video Smoke Detection detectors the potential fire
hazards must first be identified. The client or consultant will need to perform the risk assessment
and identify the nature and area of risk within the detector field of view.
