Firealarm is an official term used to describe a device which detects and raises the alarm when fire and smoke is detected. It is designed to detect even minute amounts of smoke as soon as it appears in an area – usually set off by a heat or smoke sensor that picks up any changes in temperature and/or the presence of smoke particles. Firealarms come in all shapes and sizes, from complex hardwired systems for commercial use to simple battery-operated models suitable for home use. They are seen as one of the key steps in preventing the spread of fires and can save lives if used correctly.