When does your smoke or CO alarm expire? Get the date.

Short answer

Smoke alarms need replacing 10 years from the manufacture date, not the install date. One made 15 March 2017 should be replaced by 15 March 2027. CO alarms vary by maker, so enter the life printed on yours. This is a reminder, not a safety inspection: use certified alarms and test them monthly.

How it works, with a worked example

The US Fire Administration says smoke alarms need to be replaced 10 years from the manufacture date, and that the date is what matters, so the tool starts from the manufacture date and not when you installed it. For 10-year lithium battery alarms it says to follow the manufacturer's instructions. For carbon monoxide alarms, Ontario and Health Canada both tell you to replace them as the manufacturer recommends, and Ontario notes a chirp can mean a low battery or that the alarm has reached its end-of-life, so check the manufacturer's instructions. No single number applies to every CO alarm, so you enter the life on your label. A combination alarm uses the shorter of 10 years and your CO life.

Worked example. A smoke alarm manufactured 15 March 2017 plus 10 years is 15 March 2027. On 8 October 2026 that leaves 158 days, so it is within its service life and flagged as due within 90 days once 15 December 2026 passes. A CO alarm made 1 June 2020 with a 7-year label life should be replaced by 1 June 2027.

Write the replace-by date on the alarm or on your calendar, as Health Canada suggests. Health Canada also says to check the expiry date of your alarms and replace them when necessary.