Used where a smoke detector cannot be used because of false alarm problems such as smoke, condensation or dust. This would be in areas like kitchens or boiler rooms which have fluctuations in temperatures.
Heat detectors - rate of rise
These detectors work by sensing a sharp rising change in temperature and are not to be used in a kitchen or boiler room where the temperature can rise and fall quite rapidly. The ideal place would be a garage where fumes restrict use of smoke detectors, or a dusty environment.