This guide has no affiliate links.
Smoke alarms wear out. NFPA says every smoke alarm must be replaced 10 years after its manufacture date, yet an NFPA survey found only a small percentage of people know how old their alarms are (as reported by the Air Force Special Operations Command). Here’s how to find that date, what the 10-year rule means for each kind of alarm, how carbon monoxide (CO) alarms differ, and a free printable tracker to keep it all on one page.
Emergency
In a fire, get out and call 911. Get everyone out first, call from outside, and never go back in for belongings.
The rules in one table
| Alarm | Test | Battery | Replace the alarm |
|---|---|---|---|
| Smoke alarm, 9-volt battery | Monthly | Replace at least once a year | 10 years from the manufacture date |
| Smoke alarm, sealed 10-year battery | Monthly | Sealed, not replaceable | According to the manufacturer’s instructions (USFA) |
| Hardwired smoke alarm | Monthly | Replace the backup battery at least once a year | 10 years from the manufacture date |
| CO alarm | At least monthly | Per the manual | According to the manufacturer’s instructions (NFPA); Kidde, for example, lists 7 or 10 years by model |
How to find the date on your alarm
- Remove the alarm from the ceiling or wall, usually by twisting it off its mounting plate. For a hardwired alarm, Knightdale’s fire department says to turn off the power and follow the maker’s instructions, or call a qualified electrician.
- Look at the back or side for the date of manufacture. Baltimore County’s fire marshal and the Air Force fire guidance point to the back; Knightdale’s fire department says the back or side.
- Add 10 years. That’s the replace-by date for a smoke alarm, counted from manufacture, not from when you bought it.
- Write the replace-by date on the tracker, and on the alarm or a sticker near it if you like.
- Put it back and press the test button.
No date? Baltimore County’s fire marshal says that if you can’t find a date, the smoke alarm needs to be replaced.
Test every alarm monthly
NFPA and USFA both say to test smoke alarms at least once a month by pressing the test button; NFPA says the same for CO alarms. If a smoke alarm doesn’t sound, NFPA says to change its battery, or replace the whole unit if it’s more than 10 years old.
Learn the sounds
| Sound | What it means | What to do |
|---|---|---|
| 3 loud beeps, repeating | Smoke or fire (NFPA) | Get out, call 911, stay out |
| 4 beeps and a pause, repeating | Carbon monoxide (NFPA) | Get to fresh air right away, then call 911 |
| 1 chirp every 30 or 60 seconds | Low battery (NFPA) | Change the battery; a sealed 10-year alarm gets replaced |
| Chirping that continues after a new battery | End of life (NFPA) | Replace the alarm |
CO alarms are different
CO alarm lifespans are set by each maker, so NFPA says to replace them according to the manufacturer’s instructions. Kidde, for example, says its CO alarms made since 2013 mostly have a 10-year life (with a few named exceptions) and older ones seven years. It also says an alarm in end-of-life mode can no longer detect CO. A combination smoke/CO alarm should be replaced at its end-of-life signal or 10 years from manufacture, whichever comes first, according to the Town of Knightdale, North Carolina fire department.
Where they go: NFPA says CO alarms belong in a central location outside each sleeping area, on every level of the home, and anywhere else your local code requires.
Verify locally
The 10-year replacement rule for smoke alarms comes from NFPA 72, National Fire Alarm and Signaling Code, as cited by the Knightdale and Air Force fire guidance below. We haven’t read the code text itself, so we can’t give the edition and section. States and towns also set their own alarm laws (Maryland, for example, requires sealed 10-year alarms to replace battery-only ones). Verify locally: your local code or fire marshal has the final say.
Free printable: replace-by tracker
One line per alarm: location, type, power, manufacture date and replace-by date, plus 12 monthly test boxes. It also has the battery rules, the sounds and four cut-out “replace by” reminders.
Alarms are only half of getting out. If anyone sleeps upstairs, our fire escape ladder guide covers a second way out.
Where this guide stops
This guide covers replacing and testing alarms you already have. It doesn’t cover which new alarm to buy or wiring work: NFPA and USFA say only qualified electricians should install hardwired smoke alarms. Many fire departments will check or install battery alarms; call your department’s non-emergency number.
FAQ
How often should smoke alarms be replaced?
Every 10 years from the date of manufacture (NFPA, USFA), or sooner if the alarm fails a test with a fresh battery or keeps chirping after a battery change.
Where is the date on a smoke alarm?
On the back or side of the alarm. Take it down from the ceiling or wall to read it.
Do carbon monoxide alarms last 10 years too?
It depends on the model. NFPA says to replace CO alarms according to the manufacturer’s instructions. Kidde, for example, lists a 10-year life for most models made since 2013 and seven years for older ones.
Does a 10-year sealed battery alarm still need testing?
Yes. USFA says to test it monthly and replace the whole alarm according to the manufacturer’s instructions.
More free fire-safety tools: the printable home fire escape plan grid and the escape ladder sizing chart.
Last reviewed: October 21, 2026. General information, not professional advice.
Sources
- NFPA — Smoke Alarm Information (test monthly, replace 10 years after manufacture, sounds, placement). https://www.nfpa.org/education-and-research/home-fire-safety/smoke-alarms
- NFPA — Carbon Monoxide Safety (placement, test monthly, replace per manufacturer). https://www.nfpa.org/education-and-research/home-fire-safety/carbon-monoxide
- NFPA blog — Smoke Alarm Troubleshooting (2022; temporal 3 and 4 patterns, chirps, end of life, instructions on the back of the alarm). https://www.nfpa.org/news-blogs-and-articles/blogs/2022/02/11/smoke-alarm-smoke-detector-troubleshooting
- U.S. Fire Administration — Smoke Alarms (10 years from manufacture; maintenance by power type; electricians for hardwired). https://www.usfa.fema.gov/prevention/home-fires/prepare-for-fire/smoke-alarms/
- Baltimore County Fire Marshal — About Maryland’s Smoke Alarm Law (date printed on the back; no date means replace). https://www.baltimorecountymd.gov/departments/fire/fire-marshal/smoke-alarm-law
- Town of Knightdale, NC Fire — Smoke Alarm (NFPA 72 10-year rule; date on back or side; combination alarms). https://www.knightdalenc.gov/fire/educational-outreach-fire-prevention-and-life-safety/smoke-alarm
- Air Force Special Operations Command — Every smoke alarm has an expiration date (NFPA 72; date on the back). https://www.afsoc.af.mil/News/Article-Display/Article/972455/every-smoke-alarm-has-an-expiration-date-whats-yours/
- Kidde — When Should I Replace My Carbon Monoxide Alarm? (maker states: 7- or 10-year life by model; end-of-life mode). https://www.kidde.com/support/carbon-monoxide-alarms/replacement