The short answer
In NSW, every home and other building where people sleep must have at least one working smoke alarm on each level (storey), and the alarms must comply with Australian Standard AS 3786. That applies to owner-occupied homes, rentals, caravans and moveable dwellings. In an existing home, battery-powered alarms are allowed. New homes, and some building work, must have smoke alarms connected to mains power and interconnected under the National Construction Code. Fire and Rescue NSW recommends going well beyond the legal minimum, with interconnected photoelectric alarms in every bedroom, living area, hallway, stairway and the garage.
Where the rules come from
Smoke alarms aren't a Wiring Rules (AS/NZS 3000) requirement. In NSW they are required by planning and building law and, for rentals, tenancy law:
- The NSW smoke alarm law started on 1 May 2006 under the Building Legislation Amendment (Smoke Alarms) Act 2005. The requirement now sits in Part 13, Division 2 of the Environmental Planning and Assessment (Development Certification and Fire Safety) Regulation 2021.
- The National Construction Code (NCC) sets the rules for new homes. NSW currently uses NCC 2022. NSW will adopt NCC 2025 on 1 May 2027, so it doesn't apply here yet.
- The Residential Tenancies Act 2010 and Residential Tenancies Regulation 2019 add maintenance duties for landlords. See smoke alarms in rental properties.
Fire and Rescue NSW has a plain-English summary on its smoke alarms page.
Existing homes: the legal minimum
For an existing home in NSW, the law requires:
- at least one working smoke alarm on each storey;
- alarms that comply with AS 3786.
That's it. The law for existing homes doesn't require an alarm in every bedroom, doesn't require hardwired alarms, and doesn't require them to be interconnected. You may have seen those rules quoted online, but the bedroom and interconnection requirements for all homes are Queensland law, not NSW.
A battery-only smoke alarm that complies with AS 3786 meets the minimum for an existing NSW home. Replacing the battery in a battery-only alarm is something you can safely do yourself.
New homes and building work
For new Class 1 dwellings (houses, townhouses and the like) under NCC 2022 Housing Provisions Part 9.5, smoke alarms must:
- comply with AS 3786;
- be connected to consumer mains power where mains power is supplied;
- be interconnected where there is more than one alarm, so when one goes off they all go off.
AS 3786 alarms designed for mains connection have a battery backup, so a hardwired alarm keeps working in a power cut. If you're building or doing building work that brings these rules in, your builder and certifier will set out what's required. Installing hardwired alarms is electrical wiring work, so it needs a licensed electrician and a Certificate of Compliance for Electrical Work (CCEW). See new builds.
What Fire and Rescue NSW recommends
The legal minimum is a floor, not a target. Fire and Rescue NSW (FRNSW) recommends:
- Interconnected alarms in every bedroom, living area, hallway and stairway, and the garage. In a single-storey brick home that might mean six or more alarms instead of one.
- Photoelectric alarms. FRNSW recommends the photoelectric type.
- Replacing alarms at least every 10 years. Alarms wear out. Check the date on the back of each one.
Hardwired vs battery
| Battery-only alarm | Hardwired (240 V) alarm | |
|---|---|---|
| Meets the NSW minimum in an existing home | Yes, if AS 3786 compliant | Yes |
| Required for new homes under NCC 2022 | No (mains connection required where mains power is supplied) | Yes |
| Who installs | Owner can fit it and change the battery | Licensed electrician only |
| Battery backup | Is the battery | Yes, built in under AS 3786 |
If you're upgrading an older home towards the FRNSW recommendation, Nelson can talk you through hardwired options. Hardwired alarms must be installed, repaired and replaced by a licensed electrician, and the work is certified with a CCEW lodged through the Building Commission NSW eCert portal. See smoke alarm installation.
Looking after your alarms
- Press the test button regularly so you know it works.
- Replace removable batteries as the manufacturer says (landlords must do it every year).
- Replace the whole alarm at least every 10 years, or sooner if the manufacturer says so.
- Never remove or disable an alarm, even if it goes off when you cook. If it keeps false alarming, it may be in the wrong place or near the end of its life.
Common questions
How many smoke alarms do I need in NSW?
By law, at least one working AS 3786 smoke alarm on each storey of your home. Fire and Rescue NSW recommends more: interconnected alarms in every bedroom, living area, hallway and stairway, and the garage.
Do smoke alarms have to be hardwired in NSW?
Not in existing homes, where AS 3786 battery alarms meet the legal minimum. New homes under NCC 2022 must have alarms connected to mains power where it is supplied, and interconnected if there is more than one.
Do smoke alarms need to be in every bedroom in NSW?
Not by law for existing homes. It is a Fire and Rescue NSW recommendation, and a legal requirement in Queensland, not NSW.
How often should smoke alarms be replaced?
Fire and Rescue NSW advises replacing smoke alarms at least every 10 years. For rentals, the law says within 10 years of manufacture, or sooner if the manufacturer says so.
Can I install a hardwired smoke alarm myself?
No. Hardwired alarms are connected to your electrical installation, and DIY electrical work is illegal in NSW. You can fit a battery-only alarm and change its battery yourself.