How long do smoke and CO detectors last

Smoke and CO detectors are the one household clock with the end date printed on the device. A smoke detector lasts 10 years, a CO detector 7 to 10, a fire extinguisher 5 to 10. There is no repairing them past the date: the sensor has a fixed working life, and the clock runs from the date of manufacture stamped on the back, not the day you fitted it. This is the rare component where the honest advice is to replace on schedule and not think harder than that.

What each device lasts

Device	Typical lifespan	What ends it
Smoke detector	10 years (fixed)	sensor drift, battery failure
CO detector	7–10 years	sensor end-of-life, battery failure
Fire extinguisher	5–10 years	pressure loss, agent degradation

These figures come from the product standards and manufacturer replace-by dates behind the planning model. For smoke alarms the standard is EN 14604, which sets a replace-by date, typically ten years from the date of manufacture, after which the sensor can no longer be trusted to detect. That single detail is the one most people get wrong: the ten years is counted from when the unit was made, so an alarm that sat in a warehouse or a drawer for two years before fitting is already two years into its life on the day it goes up.

There is no repair, only replace

Every other component in a house invites a repair-or-replace question; these do not. A smoke or CO detector has a sealed sensor with a fixed working life, and once it is spent the device is at the end of its use, not in need of a part. That is why this page carries no repair calculator: there is no repair path to price. A chirping alarm is either a flat battery, a two-minute fix, or a unit at its replace-by date, a whole-unit change. The fire extinguisher is the near-exception: it can be serviced and refilled where a professional check says the body is sound, but a unit that has lost pressure or whose agent has degraded is replaced.

The clock you watch

Two dates matter, and only one is on your calendar. The battery is a short sub-cycle: a replaceable battery is a yearly change, a sealed ten-year battery runs the life of the unit. Setting the device’s end date is the replace-by date, and because it runs from manufacture you cannot read it off the day you moved in. What removes the guesswork is to read the printed date on each unit once, note the replace-by year, and test the alarm monthly in between. A monthly test confirms the battery and sounder; it does not extend the sensor, which ages on its own regardless of how often it passes a test.

When to plan

Astrid’s flat in Gothenburg has smoke alarms fitted when she moved in five years ago, which felt recent until she read the manufacture date on the back: they were made three years before that, putting them eight years into a ten-year life, not five. Knowing that turns a vague future job into a dated one. She notes the replace-by year for each alarm and for the CO detector by the boiler, and buys the replacements the year before they expire rather than the week one starts chirping in the night. The version that goes wrong is discovering a dead alarm during a real one.

What this means before you call anyone

These are the cheapest components in the house and the one clock worth never missing, which is reason enough to write the dates down somewhere they will resurface on time. Read the manufacture date on each unit, note the replace-by year, and let something other than a 3am chirp do the reminding. The plan in appkeep holds the replace-by year for each detector and the extinguisher’s service date as fixed lines, so the one lifespan in the house with no repair option is also the one you never have to hold in your head.