The XP95 IS Heat Detector is distinguishable from XP95 IS smoke detectors by its low air-flow resistance case which allows good contact between the sensing thermistor and the surrounding air. The device monitors temperature by using a single thermistor network which provides a voltage output proportional to the external air temperature.
 
The voltage signal is processed and transmitted to the control equipment in the same way as in the case of the ionisation smoke detector. Full details of the principles of operation and the electrical description are published in the XP95 Engineering Product Guide. XP95 IS detectors have the same operating characteristics as the standard versions.