The Fyreye MkII optical smoke detectors use a pulsing IR LED & photodiode to detect IR scatter caused by smoke entering the chamber. The detector is particularly suitable for detecting optically dense smoke, involving materials such as soft furnishings, PVC, plastic, foam and all similar materials which produce small visible particles (0.5 to 10μm). The Fyreye Rate of Rise heat detectors (MKII-HR) use a thermistor arrangement to sense a quick rise in temperature and also a final threshold temperature of 57°C. The Fyreye fixed heat detector (MKII-HF) has a single thermistor arrangement that gives an alarm at a temperature of 57°C. There are 4 types of mounting base available; standard or deep and with or without diode.