Fireclass 601PH Conventional High Performance Optical Smoke Detector forms part of the series 600 range of plug in detectors for ceiling mounting. 601PH detectors react to the complete range of fire products, from slow smouldering fires, producing visible particles to open flaming fires producing large numbers of very hot smaller sized aerosols. The combination of optical and heat technology allows detection of clear burning fire products which until now could only be detected by ion-chamber detectors. For normal ambient conditions 601PH will behave as a normal optical smoke detector, only when a rapid rise in temperature is detected does the sensitivity of the detector increase and the presence of smoke will confirm a fire condition which will be transmitted as an alarm level.