Optical beam smoke detectors are specifically appropriate for preserving structures with big open up spaces like warehouses, atriums etcetera. Optical beam smoke detectors are uniquely suited to preserving buildings with big open places with large ceilings such as a warehouse or atrium. The OSI-R-SS detector is really a mixed transmitter/receiver https://www.firesense.co.uk/type/conventional-fire-system/conventional-beam-detectors/