Ampac Orbis, Product Manual, Page: 7 / 22

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MAN1509-4
ORBIS AUSTRALIAN PRODUCT GUIDE
5 Where to use optical smoke detectors
Optical smoke detectors have always been recognised as good detectors for general use. They are
regarded as particularly suitable for smouldering fires and escape routes.
The performance of Orbis optical detectors is good in black as well as in white smoke. In this respect
Orbis is different from traditional optical smoke detectors which perform far better in white smoke
than in black.
Orbis optical detectors are

Also designed to significantly reduce the incidence of false alarms from transient
phenomena

Are recommended for use as general purpose smoke detectors for early warning of fire in
most areas
5.1 Orbis optical smoke detector
The sensing technology in the Orbis optical smoke detector is significantly different in design from
previous optical detectors. A full description is given in the section ‘How does Orbis optical smoke
detectors work?’ but the advantages of this system and its associated algorithms are:
Improved sensitivity to black smoke
Compensation for slow changes in sensitivity
Extra confirmation of smoke before alarm signal given
The algorithms are used to verify signals from the sensing chamber, to filter out transients and to
decide when the detector should change to the alarm state.
All this combines to increase detection reliability and reduce false alarms.
5.2 How does the orbis optical detector work?
Orbis operates on the well established light scatter principle. The remarkable optical design of the
Orbis optical smoke detector allows it to respond to a wide spectrum of fires.
The sensing chamber of the Orbis optical smoke detector contains an optical sensor which
measures back-scattered light as well as the more usual forward scattered light. As a result
sensitivity to black smoke is greatly improved.
The detector is calibrated so that Orbis is highly reliable in detecting fires but is much less likely to
generate false alarms than ionisation smoke detectors.
The stability of the detectors high reliability and low false alarm rate is further increased by the use of
algorithms to decide when the detector should change to the alarm state. This removes the
likelihood of a detector producing an alarm as a result of smoke from smoking materials or from
another non-fire source.
The sensing chamber has been designed to keep out dust and other airborne contaminants.
5.3 Environmental performance
Orbis optical detectors operate over a broad range of voltages at extremes of temperature. This
operating voltage is 8.5V to 33V at
–40° to +70°C which is a unique achievement for a conventional
smoke detector.