6
At installation, the maximum deviation in any direction from the central
optical axis should not exceed 5 degrees for transmitters and 15 degrees for
receivers as shown in Figure 1.
Figure 1
After fixing of a transmitter and receiver durable angular deviation from the
originally installed position should not exceed 2 degrees. This should be considered
when installing the detector components on structures that can deform with time.
2.4 The line of sight between the transmitter and the receiver always has to
be clear and may not be interfered by moving objects (e. g. overhead crane).
Heat accumulation under the roof may prevent smoke from rising up to the
ceiling. Thus, the detector must be mounted below the expected heat accumulation.
Since the smoke from a fire does not simply rise straight up, but rather
spreads like a mushroom cloud (depending on air current and accumulation), the
monitoring range is much greater than the diameter of the IR beam.
The maximum distance between two detectors with parallel IR beams is
determined by national standards. The minimum distance between the two
detectors is not regulated.
The centre line of the monitoring beam may not be closer than 0.25 m to
walls, ceilings, furniture or stored goods.
