A heat detector warns you of fire hazard situations in the home, garage, or office. This is especially useful in areas where a standard smoke detector doesn't work properly. The sensor in a smoke detector also reacts to steam or dust, which isn't always useful in a kitchen, for example. Heat detectors react when the temperature in a room exceeds 55 degrees. This way, you won't receive unjustified reports of steam development, but reports of the start of a fire.