Ampac Orbis, Product Manual, Page: 6 / 22

4
MAN1509-4
ORBIS AUSTRALIAN PRODUCT GUIDE
Question:
So what is the best way to choose a heat detector?
Answer:
To make things easier we have produced a flow chart (see Figure 3).
Question:
Should I use optical detectors to detect smoke in all applications?
Answer:
As stated, optical detectors have long been recommended as good general purpose smoke
detectors. Laboratory tests have been carried out to compare the performance of optical detectors in
the standard test fires described in the Australian Standard AS7240.
The results of these tests are given in Figure 1. The graph shows the acceptable response in terms
of smoke density which is given as, ‘m’ on the y axis. Detectors must respond before the end of test
which is an ‘m’ = value of 2. The performance of Orbis detectors is given as a solid line which shows
how evenly the optical detectors respond to the test fires.
If detectors respond too quickly (the lower shaded portion of the graph) they may be too sensitive
and hence likely to generate false alarms.
If detectors respond too slowly (the upper shaded portion) they are in danger of not changing to the
alarm state before the end of test.
An even response in the centre is the ideal response.
2.00
1.50
1.00
0.50
0.00
TF2 TF3 TF4 TF5
Too Sensitive
Acceptable
Values
Poor
Optical
Density
Values
( m value )
Test Fires
Figure 1: Orbis Optical Detector Response to Test Fires
2.00
1.50
1.00
0.50
0.00
Too Sensitive
Acceptable
Values
Poor
Optical
Density
Values
( m value )
Test Fires
Orbis Optical
Orbis Multisensor
Figure 2: Comparisons to Response Between Orbis Optical & Multisensor