US Patent 7817049 Combined scattered-light and extinction-based fire detector

A fire detector has at least two sensor units for monitoring a confined space for the occurrence of a fire. A first fire parameter is monitored according to the scattered light method, using a first sensor unit located at or in the vicinity of the ceiling. At least one second sensor unit of the fire detector, which emits at least two highly focused light beams towards the floor of the confined space, monitors a second fire parameter according to the extinction method.