Version: 20210708
11
Camera positioning
SITE ASSESSMENT
For maximum protection, it is recommended to perform a site survey before installing cameras with Araani Fire
Guard. This allows you to identify risk areas and take those into account when positioning new cameras.
•
Define the hot spots:
What is the type of risk? Can the fire start at any location in the field of view or is there specific risk related
to a machinery or a critical part of a scene?
•
For smoke detection, estimate the smoke flow:
Estimate where smoke may flow in case of an incident. Dependent on this estimation, preferably select a
camera position that will visualize the smoke in the fastest and largest way. Focus on where the smoke
will flow, rather than the risk area.
Will smoke ascend to the ceiling or will there be stratification?
Will smoke be dispersed over the whole area by ventilation or forced air flow?
•
System redundancy:
To guarantee full coverage on very large areas, multiple cameras will be needed. To avoid blind spots,
make sure the field of views of the cameras overlap with a minimum of 20%.
CAMERA POSITION / FIELD OF VIEW
Based on the site assessment, preferably select a camera position that maximizes the visualization of potential
smoke or flames.
•
At default sensitivity level, Araani Fire Guard algorithm will trigger alarm when smoke covers
approximately 3% of the field of view during 5 seconds at the same location in the field of view.
•
Araani Fire Guard algorithm will trigger alarm when the flame size exceeds 0,2% of the field of view and
the flame was detected for at least 20 seconds at the same location in the field of view.
For a camera with 1920 x 1080 resolution, 3% is a zone of 249 x 249 pixels and 0,2% is a zone of 64 x 64 pixels.
As an indirect result: the smaller the field of view, the higher the sensitivity, and the further away from the camera,
the lower the sensitivity.
The minimum required coverage for smoke and flames to be recognized depend on the sensitivity setting as per
table below.
Sensitivity setting
Minimal smoke size
(% of field of view)
Minimal flame size
(% field of view)
1
4%
0,5%
2
3%
0,3%
3
3%
0,2%
4
2%
0,15%
5
1%
0,1%
Below is a graphical representation of smoke and flame detection threshold for different sensitivity settings on a
1920 x 1080 image, assuming a 1:2 aspect ratio of smoke clouds.
