Heat Detectors

In the UK, it is required that heat detectors must detect a pre-determined fixed temperature, and may also respond to a pre-determined rate of rise of temperature. Heat detectors that operate only when the rate of rise of temperature is abnormal do not comply with BS EN 54-5 and ought not to be used. Why? So that fires which smolder and build up slowly can be detected (the detector responds to the temperature of the fire, however quickly it builds up). British Standard (BS) 5445 (Part 5) identifies three different grades of detector according to how quickly it operates over a range of rates of temperature rises (to a maximum of 78°).

In some environments, such as furnace rooms or transformer rooms, high temperature heat detectors are necessary, with temperatures between 90° and 160° (see BS 5445 (Part 8)).

A grade and range system is used to categorise heat detectors: grade 1 heat detectors are more sensitive and may therefore be installed on higher ceilings than grades 2 and 3.