Smoke & CO detectors — the schedule that matters
Test every smoke and CO alarm monthly, and replace the whole unit — not just the battery — on schedule: smoke alarms at 10 years from the manufacture date, CO alarms every 7–10 years per the model. Put smoke alarms on every level, inside each bedroom, and outside each sleeping area; CO alarms near sleeping areas and on every level. These are the cheapest life-safety items in the house.
| Task | How often | Why |
|---|---|---|
| safetyTest every smoke and CO alarm (press the button) | Monthly | Confirms the alarm and battery work |
| safetyReplace batteries (non-sealed units) | Yearly, or when it chirps | A chirp means low battery |
| safetyReplace smoke alarm units | At 10 years from manufacture date | Sensors degrade; the whole unit expires |
| safetyReplace CO alarm units | Every 7–10 years per the model | CO sensors have a limited service life |
| safetyCheck placement: every level, in/near each bedroom | Once, then after any renovation | Coverage gaps leave rooms unprotected |
Replace the unit, not just the battery
The sensor inside an alarm wears out even if the battery is fresh. Check the manufacture date printed on the back; if a smoke alarm is 10 years old, replace the whole unit. Sealed 10-year-battery alarms are replaced as a unit at end of life. If a CO alarm sounds, treat it as real — get to fresh air and call 911.
When to call a professional
- • Hardwired/interconnected alarms you're not comfortable replacing — use an electrician.
- • A CO alarm sounding — get out and call 911; then have the source found before re-occupying.
Common questions
- How do I know how old my alarm is?
- There's a manufacture date printed on the back or side. If there isn't one, it's old — replace it.
- Combination smoke/CO alarms — good idea?
- They simplify coverage, but follow the shorter replacement interval of the two sensors and place them where both risks apply.
Sources
- Test smoke alarms monthly. Tier 2 (standards/extension)
National Fire Protection Association (NFPA) · verified 2026-07-26 - Replace smoke alarms at least every 10 years from the date of manufacture — including 10-year-battery and hardwired units. Tier 2 (standards/extension)estimate · has commercial bias
First Alert (citing NFPA) · verified 2026-07-26 - If a CO alarm sounds, get everyone to fresh air outside immediately and call 911; do not go back in to find the source. Tier 1 (official)
U.S. Centers for Disease Control and Prevention (CDC) · verified 2026-07-26