This paper describes the development and performance of a multisensor two-stage fire detection and water discharge algorithm. The objective was to detect fire at an early stage, sound an alarm and, if nece:Β’sary, trigger the automatic extinguishing system before conditions woui'd become untenable for the occupants of the room of fire origin. The .fire detection system incorporated commercially available analogue addressable sensors linked to a personal computer which controlled the communications with the fire sensors, processed the detection algorithm and also triggered the discharge of water from two open head sprinklers. The sensors were installed in a 4.0 m long by 3.6 m wide by 2.4 m high room and subjected to a range of smouldering and flaming fire scenarios. The performance of the system was assessed at different detection algorithm sensitivities. The multi-sensor detection algorithm was compared with a threshold detection algorithm to examine their respective effectiveness of providing an early warning to the occupants. The false alarm rejection capabilities of the detection algorithm were also examined. A range of representative false alarm tests were conducted and the results used, in conjunction with those from the fire tests, to select the most appropriate sensitivity for the algorithm. Crown