A smoke detector is a device which alerts people in the event of a fire. Smoke alarms work on two different detecting principles. The first being Ionisation and the second Photoelectric. It is good to have a combination of both alarms in different areas of your house. By law all new houses must have smoke detectors installed inside the premises. Also if you are renting a property you must have a working smoke detector installed in the premises. Smoke detectors can be interconnected and also hard wired with a battery backup incase of power failure. Smoke detectors need to be replaced every 5-10 years. All smoke detectors sold here are ActiveFire listed and Australian Standards Approved. All hard wired smoke detectors must be installed by a licensed electrician.