---
title: "Does Smoke alarms expire? Unsafe or ineffective after the date"
description: "Ten years from manufacture, then the whole unit — not just the battery. What actually changes over time, whether it matters, and how to store it."
url: https://atoneplace.net/does-it-expire/smoke-alarms/
site: "At One Place"
---

# Does Smoke alarms expire?

**Does Smoke alarms expire?: Ten years from manufacture, then the whole unit — not just the battery.**

10 years from the manufacture date on the back

The sensing element degrades: ionisation chambers accumulate dust and their radioactive source decays slowly, and photoelectric sensors drift as their optical surfaces age. Neither failure announces itself, and the test button checks the sounder and the battery rather than the sensor. The date is printed on the back of the unit, and a house bought second-hand very often has alarms older than the owner realises. Carbon monoxide alarms have shorter lives still, typically seven years, and are a separate device from a smoke alarm even when the two are combined.

## How to store it

- Not applicable — but replace all of them at once, since they were almost certainly installed together.

## How to tell it has gone

- None. The date on the back is the only guide.
- Chirping usually means a low battery, not end of life; some units chirp differently at end of life.

> "Use by" and "best before" are legally different. Use-by is a safety date and should be respected; best-before is about quality, and food is usually fine well past it. Where the two diverge matters, the page above says which applies.

## Common questions

### Does Smoke alarms expire?

Ten years from manufacture, then the whole unit — not just the battery.

### How long does Smoke alarms last?

10 years from the manufacture date on the back

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## Sources

- Official vendor product documentation — At One Place (/about/)