Apollo ORB-OP-12001 Optical Smoke Detector with Flashing LEDOrbis Optical Smoke Detectors work on the well established light scatter principle. The remarkable optical design of the Orbis Optical Smoke Detector enables it to respond to a wide spectrum of fires. The sensing chamber contains an optical sensor which measures back scattered light as well as the more usual forward scattered light. Sensitivity to black smoke is greatly improved.