Optical beam smoke detectors are particularly appropriate for preserving buildings with substantial open spaces which include warehouses, atriums and so on. OSI-R-SS is actually a 4-wire conventional reflector-form linear optical beam smoke detector for use in fireplace alarm programs. The beam operates primarily on the basic principle of light obscuration https://www.firesense.co.uk/type/conventional-fire-system/conventional-beam-detectors/