MaintainlyHow often should you replace your smoke detector unit (10-year)?
Replace smoke detector unit (10-year) every 10 years. The commonly recommended range is replace at 10 years. Sensors degrade; a 10-year-old alarm may not detect smoke reliably. This is a safety-critical task, so do not let it slip.
Smoke alarms expire. The US Fire Administration says they need to be replaced 10 years from the manufacture date, and that date is printed on the back of the unit. It applies whether the alarm has ever seen smoke or not.
Why does replacing your smoke detector unit (10-year) matter?
Sensors degrade; a 10-year-old alarm may not detect smoke reliably.
What happens if you skip replacing your smoke detector unit (10-year)?
An expired alarm can still chirp and still pass a button test. The button shows that the alarm has power and can sound. It tells you nothing about how old the sensor is, which is why the printed date matters.
How do you do it?
- Read the manufacture date on every unit. Twist the alarm off its base and look at the back. Replace at ten years from that date, not from when you moved in.
- Choose the sensor type. The two basic types are ionization and photoelectric. The US Fire Administration recommends having both, or dual-sensor alarms. Queensland requires photoelectric alarms, so check your local rule before buying.
- Leave mains wiring to an electrician. Battery and wireless alarms are a homeowner job. If the existing alarms are hard-wired, the replacement is electrical work: Queensland Fire Department says hardwired alarms must be installed by a qualified electrician.
- Replace all of them together. They were almost certainly installed on the same day, so they expire on the same day.
- Test the interlink. Trigger one alarm and confirm every other alarm in the house responds.
- Write the install date on the new units. Marker on the side. Ten years is long enough that you will not remember.
What does it take?
How do you know replacing your smoke detector unit (10-year) is overdue?
- A manufacture date more than ten years old
- Repeated false alarms, which can mean a dusty or ageing sensor
- No date at all on the unit, which means it is old enough to replace on principle
What do people get wrong?
- Dating replacement from purchase rather than from the printed manufacture date
- Replacing only the alarm that failed, leaving its identically aged siblings in place
- Keeping an alarm that nuisance-trips near the kitchen until someone disables it. Ontario’s Fire Marshal suggests moving it or replacing it with a photoelectric type
- Mixing brands on an interlinked system without checking they are compatible
What changes how often you need to do it?
- Combination smoke and CO units carry their own replace-by date, which can be earlier than a smoke-only alarm’s. Follow the date on the unit
- London Fire Brigade advises a heat alarm in the kitchen, and fitting smoke alarms away from kitchens and bathrooms, where steam can damage them or set them off
- Wireless interlinked alarms simplify retrofit where running cable is impractical
When should you stop and call someone?
Hard-wired alarms are a job for an electrician. Battery and wireless interlinked units are a homeowner job.
Does this differ in the US, UK, Australia or Canada?
United States
The US Fire Administration says to replace alarms 10 years from the manufacture date, and to replace sealed 10-year battery alarms according to the manufacturer’s instructions. In New York, new or replacement alarms sold since April 2019 must have a sealed 10-year battery or be hard-wired, which makes the battery life and the expiry date the same date.
United Kingdom
The government’s guidance for landlords in England points to alarms that comply with BS 5839-6 and prefers sealed for life batteries over replaceable ones. London Fire Brigade recommends alarms with a 10 year sealed battery. Scotland’s interlinked alarm requirement means replacements need to work as part of an interlinked set rather than as standalone units.
Australia
In New South Wales, alarms must meet Australian Standard AS 3786, and landlords must replace them within 10 years of manufacture, or earlier if the manufacturer says so. Queensland requires photoelectric alarms marked AS 3786-2014, interconnected so they all sound together, and tells owners to replace any alarm more than 10 years old. If your current alarms are hardwired there, the replacements must be hardwired too.
Canada
Ontario’s Fire Marshal says all smoke alarms wear out and should be replaced every 10 years according to the manufacturer’s instructions. Homeowners are responsible for installing and maintaining alarms, and landlords for making sure rental properties comply. Look for the logo of a recognized testing agency such as CSA or ULC.
Frequently asked questions
Why does replacing your smoke detector unit (10-year) matter?
Sensors degrade; a 10-year-old alarm may not detect smoke reliably.
What happens if you skip replacing your smoke detector unit (10-year)?
An expired alarm can still chirp and still pass a button test. The button shows that the alarm has power and can sound. It tells you nothing about how old the sensor is, which is why the printed date matters.
Does replacing your smoke detector unit (10-year) differ by country?
Universal. The US Fire Administration and Ontario advise replacing alarms 10 years from the manufacture date. AU: alarms must comply with AS 3786 and QLD requires interconnected photoelectric alarms in every bedroom, so the set is usually replaced together.
How we put this together
The figures, intervals and legal points on this page were checked against the sources listed below. The default interval and accepted range are the ones Maintainly uses in its task library. Costs and times are typical ranges and vary by region and by home. Your own manufacturer's instructions come first, and gas, electrical and structural work belongs with a qualified professional. How we research and write.
Sources
- Smoke alarms, US Fire Administration. Checked 11 October 2026.
- New residential smoke alarm sales requirements go into effect April 1, New York Department of State. Checked 11 October 2026.
- Smoke and Carbon Monoxide Alarm (England) Regulations: guidance for landlords and tenants, GOV.UK. Checked 11 October 2026.
- Smoke alarms and heat alarms, London Fire Brigade. Checked 11 October 2026.
- Fire and smoke alarms: the law, Scottish Government. Checked 11 October 2026.
- Smoke alarm laws are changing in Queensland (fact sheet), Queensland Fire Department. Checked 11 October 2026.
- Smoke alarms: what is the law?, Fire and Rescue NSW. Checked 11 October 2026.
- Fire safety at home, Government of Ontario. Checked 11 October 2026.
- Smoke detector installation cost, HomeGuide. Checked 11 October 2026.
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