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. Orbis I.S. Optical Smoke Detectors are also designed to reduce significantly the incidence of false alarms through over-sensitivity to transient phenomena. Orbis I.S. Optical Smoke Detectors are recommended for use as general purpose smoke detectors for early warning of fires in most areas.