A Heat Detector is a device that responds to changes in ambient temperature. Typically, if the ambient temperature rises above a predetermined threshold an alarm signal is triggered. Heat detectors can also be further broken down into two main classifications of activation, "rate-of-rise" and "fixed". Rate of rise detectors look for  dramatic changes in the ambient temperature of an area. Fixed detectors will alarm when a certain temperature is reached.

Common locations for Heat detectors are kitchens, attics, laundry rooms, garages, lower boathouses, crawl spaces and utility rooms.