Under Northern Territory law, approved smoke alarms must be installed in all residential premises or movable dwellings. This includes caravans. Home owners must test each smoke alarm at least once every 12 months.
An approved smoke alarm is a photoelectric type smoke alarm that is either hardwired to your home's power supply or has a sealed lithium battery unit with a 10-year life. Hardwired smoke alarms must be installed by a licensed electrician. Battery-powered smoke alarms can be manually installed according to the manufacturer’s instructions.
To read more, visit Northern Territory Government