The Optical Beam Smoke Detector works on the principle of light obscuration. The photosensitive element of the Optical Beam Smoke Detector sees light produced by the Transmitter in a normal condition. The Receiver is calibrated to a preset sensitivity level based on a percentage of total obscuration. There are two general types of Optical Beam Smoke Detector – Projected and Reflective. The type used will be dictated by the installation and environment conditions and constraints