How Long Do Smoke Detectors Last? (2026 Guide)

How long do smoke detectors last?

Short answer: Smoke detectors last 10 years from the date of manufacture — not the day you installed them. That is the replacement interval NFPA 72, the National Fire Alarm and Signaling Code, is built around, and it applies to battery, 10-year sealed, and hardwired units alike. Carbon monoxide and combination alarms run on a shorter, self-enforcing clock: ANSI/UL 2034 has required an end-of-life signal on CO alarms built since August 1, 2009. Flip the alarm off its bracket and read the date stamped on the back label; if it is 10 years old — or there is no date at all — replace the unit, not the battery.

The question "how long do smoke detectors last" gets asked most often at two moments: when an alarm starts chirping at 3 a.m., and when someone moves into a home with no idea what is on the ceiling. This guide gives you the full answer for every alarm type in a typical home — 9-volt battery units, 10-year sealed-battery units, hardwired interconnected units, carbon monoxide alarms, and smoke/CO combination alarms — using the manufacturer service-life rules published by Kidde and BRK/First Alert, the U.S. Fire Administration's replacement guidance, and NFPA's fire-loss research. It is written for homeowners, landlords, and facility staff who need a defensible replace-or-keep decision, and it pairs with our installation-placement guide, where to install smoke detectors.

Two facts do most of the work in this article. First, the 10-year clock starts at manufacture, so an alarm that sat in a warehouse or a junk drawer for two years owes you only eight on the ceiling. Second, the lifespan question and the battery question are different questions — replacing a 9-volt every year keeps an alarm powered, but it does not reset the sensor's service life. How long do smoke detectors last is ultimately a sensor-aging question, and no battery swap fixes an aged sensor.

Why this matters.
NFPA's Smoke Alarms in US Home Fires research found that almost three out of five home fire deaths occurred in properties with no smoke alarms (41%) or alarms that failed to operate (16%) — and that having working smoke alarms cuts the risk of dying in a reported home fire by roughly 60%. An expired alarm is the worst kind of failure because it looks fine on the ceiling: the horn may still chirp while the aging sensor responds slowly, or not at all. Age is one of the few failure modes you can eliminate with a screwdriver and a calendar.

The 10-year rule: where it comes from and when the clock starts

Manufacture date, not install date

The U.S. Fire Administration states the rule plainly: smoke alarms "need to be replaced 10 years from the manufacture date." Kidde's support guidance is just as direct — smoke alarms have a 10-year lifetime regardless of battery type, and "that time starts at date of manufacture, not start of use." An alarm still sealed in its blister pack is aging. This is why the worked example later in this guide starts with reading the date label, not with the purchase receipt.

What NFPA 72 and the fire agencies actually require

NFPA 72 is the model code that state and local building or fire codes adopt, and its household smoke-alarm provisions are the origin of the 10-year replacement interval that Kidde, First Alert/BRK, USFA, and every state fire marshal repeat. Alongside replacement at 10 years, the same public guidance carries the maintenance schedule: test every alarm monthly using the test button, replace 9-volt batteries at least once a year, and replace the backup battery in hardwired units annually. Testing monthly matters for the lifespan question because a failed test is a replace-now signal at any age — our companion piece on photoelectric vs ionization smoke detectors covers why sensor technology affects what the alarm detects, but not how long it lasts.

Smoke alarm lifespan by type

Every row in this table ends at the same place — the unit comes down at 10 years from its manufacture date — but the battery duty in between differs by design. This is the maintenance schedule the USFA publishes:

If you are choosing what goes up next, the current market is compared in our best smoke detectors 2026 roundup, with mains-powered picks in the best hardwired smoke detector 2026 guide, and the full lineup in our smoke detectors collection.

How to read the manufacture date code on the back of the alarm

Kidde's support documentation puts it in one sentence: "The manufacture date code is stamped on the label located on the back of the alarm." First Alert and BRK units carry an equivalent back-label date. Twist the alarm counterclockwise off its mounting bracket and look for a label block like this:

Kidde date labels

Kidde stamps the date of manufacture on the rear label; many recent units also print an explicit "replace by" year. Do the arithmetic from the manufacture date either way: 2019 JUL 15 + 10 years = replace no later than July 2029, regardless of when the alarm actually went on the ceiling.

First Alert and BRK date labels

First Alert and BRK print the date of manufacture on the back of the unit as well, and BRK's installer documentation adds a detail that matters for combination units: the end-of-life timer in their CO and smoke/CO alarms is "a simple counter that begins working once the unit is activated" — plugged in, hardwired, or battery-inserted. For the smoke-only 10-year rule you still use the printed manufacture date; the activation-based timer governs when a CO or combo unit will chirp itself into retirement.

No date printed? Replace it now

Date-of-manufacture labels have been standard for decades. An alarm with no legible date is old enough that the answer to "how long do smoke detectors last" has already passed — take it down and replace it the same day. The same applies to any alarm that fails a test-button check, is painted over, or visibly yellowed.

Carbon monoxide and combination alarms time out sooner — and enforce it

Smoke alarms rely on you to do the date math. CO alarms do not: ANSI/UL 2034, the product standard for residential CO alarms, was changed to require an end-of-life feature on all CO alarms and combination smoke/CO alarms, applying to units produced from August 1, 2009 onward. When the internal timer expires, BRK/First Alert units "begin to sound 5 chirps" (with some models displaying ERR or END), and the signal can only be silenced temporarily — about two days per press at first, and after two to three weeks it cannot be silenced at all. The alarm is designed to nag you into replacing it.

Two practical consequences follow. First, on a combination unit the CO sensor's clock is the binding one — the smoke side does not buy the CO side extra time. Second, because the CO timer starts at activation rather than manufacture, a combo unit's chirp date depends on when you installed it, which is one more reason to write the install date on the bracket. Placement rules and state-by-state CO mandates are covered in our carbon monoxide detector requirements by state reference, the hardware lives in our carbon monoxide detectors collection, and detached-structure placement is covered in the best garage CO detector guide.

Low-battery chirp or end-of-life chirp? How to tell before you waste a battery

Both signals are a short chirp at long intervals, and mistaking end-of-life for low battery is how expired alarms stay on ceilings. The decode below follows the manufacturers' published signal guides — patterns vary by model, so confirm against the manual for your unit:

Worked example: deciding whether a smoke detector has lasted long enough

Here is the whole decision on a real bedroom alarm, using products stocked in our smoke detectors collection. As an Amazon Associate, WC Safety earns from qualifying purchases made through the Amazon buttons below.

1. Take the alarm down and read the back label. Twist counterclockwise off the bracket. Find the manufacture date — for this example, a battery photoelectric unit stamped 2017 MAR 03.
2. Do the 10-year math from the manufacture date. 2017 + 10 = replace by March 2027. It is within a year of expiry — this one comes down now rather than earning a fresh 9-volt.
3. Pick the replacement class deliberately. For a no-maintenance swap, a 10-year sealed unit such as the Kidde P3010B photoelectric smoke alarm eliminates annual battery changes for its whole service life. Check Kidde P3010B on Amazon
4. Match hardwired with hardwired. If the old unit was interconnected on mains power, replace in kind — the BRK 9120B hardwired smoke alarm is the standard interconnectable pattern with battery backup. Check BRK 9120B on Amazon
5. Consider consolidating smoke and CO where both are required. A sealed combination unit like the X-Sense SC07 combination smoke and carbon monoxide alarm covers both hazards on one bracket; remember the combo clock runs from activation. A budget sealed smoke-only alternative is the Kidde 20SA10 sealed-battery smoke alarm.
6. Write the dates on the new unit, then verify placement. Note the manufacture date and install date on the bracket in marker, press-test the new alarm, and confirm the room-by-room layout against where to install smoke detectors. Test monthly from then on.

Frequently asked questions

How long do smoke detectors last?

Ten years from the date of manufacture, per NFPA 72, the U.S. Fire Administration's replacement guidance, and every major manufacturer's service-life documentation. The rule covers battery, 10-year sealed, and hardwired units equally. After 10 years the whole unit is replaced — there is no inspection or battery change that extends it. Start with the date stamped on the back label, as shown in this guide's worked example.

Does the 10-year clock start at installation or at manufacture?

At manufacture. Kidde's guidance is explicit that the 10-year lifetime "starts at date of manufacture, not start of use," and the USFA phrases the rule the same way. Time in a warehouse or drawer counts against the alarm, which is why checking the label beats trusting the purchase date.

How do I find out how old my smoke detector is?

Twist it off the bracket and read the manufacture date code stamped on the rear label — Kidde documents this location in its manufacture-date support article, and First Alert/BRK label the back of their units the same way. If no date is legible, the alarm predates modern labeling and should be replaced immediately.

Do hardwired smoke detectors also expire after 10 years?

Yes. Mains power keeps the horn loud but does nothing for sensor aging, so hardwired units follow the same 10-year manufacture-date rule — and per USFA guidance, their backup battery still needs a change at least once a year along the way.

How long do 10-year sealed-battery smoke alarms last?

The sealed lithium battery and the sensor are designed to expire together at the 10-year mark, which is the whole point of the format — no annual battery duty, one replacement event. When a sealed unit like the Kidde P3010B chirps end-of-life, the unit is done by design.

How long do carbon monoxide detectors last?

CO alarm service life is model-specific and enforced by an internal end-of-life timer that ANSI/UL 2034 has required on units produced since August 1, 2009. Many current models, including most BRK/First Alert CO and combo units, carry a 10-year alarm and sensor life; older designs were shorter. The unit tells you when it is done.

How long do combination smoke and CO alarms last?

Until the shorter of the two clocks runs out — in practice the CO end-of-life timer, which BRK documents as starting when the unit is first activated. When a combo unit signals end-of-life, both sensing functions come down together. The X-Sense SC07 is a current sealed 10-year example.

What does one chirp every 30 to 60 seconds mean?

On most units it means low battery, but on many Kidde models the same cadence is also the end-of-life signal — which is why the date label, not the battery drawer, is the first check. If the unit is under 10 years old, replace the battery; if it is at or past 10 years, replace the alarm.

What does five chirps mean on a First Alert or BRK alarm?

BRK/First Alert CO and combination units sound a 5-chirp end-of-life pattern when the internal timer expires; digital models may show ERR or END instead. Pressing test/silence buys about two days of quiet at first, and after two to three weeks the signal can no longer be silenced. The only fix is replacement.

Can I just replace the battery instead of the whole alarm?

Only if the unit is under 10 years old. A fresh battery restores power, not sensor performance — an aged sensor with a new battery is still an expired alarm. Past the 10-year manufacture date, battery money goes toward a new unit instead; the battery-vs-whole-unit distinction comes straight from USFA's maintenance guidance.

Do smoke detectors expire if they have never been used?

Yes. Because the clock runs from the manufacture date — "not start of use," in Kidde's words — a never-installed alarm in original packaging is still aging. A unit that spent three years boxed offers only seven on the ceiling — check the label before buying deep-discount old stock.

How often should I test my smoke detector?

Monthly, with the test button, per USFA guidance — and replace 9-volt batteries at least annually. A monthly test is also your earliest warning of a dead horn or power fault, which means replacement at any age. Placement checks belong on the same monthly routine.

Do photoelectric and ionization alarms have different lifespans?

No — both sensor technologies carry the same 10-year manufacture-date replacement interval. The technologies differ in which fire type they detect fastest, which is a placement-and-coverage question rather than a longevity one; the full comparison is in photoelectric vs ionization smoke detectors.

What should I do with an expired alarm that has a sealed lithium battery?

Do not put sealed-lithium units in household trash. Lithium batteries belong at battery-recycling drop-offs or household-hazardous-waste programs, per EPA guidance — dispose of the expired unit under your local program's rules. Ionization alarms contain a tiny sealed radioactive source (Am-241); some manufacturers operate mail-back programs for them, and regular trash disposal rules vary by locality, so check locally there too.

Is replacing smoke alarms at 10 years a legal requirement?

It depends on which code your state or city has adopted. NFPA 72's household provisions — the source of the 10-year interval — become enforceable where a jurisdiction adopts them into its building or fire code, and many landlord-tenant statutes reference them. Treat 10 years as the compliance floor and check your local code; this guide is not legal advice.

Should I write the install date on the alarm?

Yes — marker on the bracket or the alarm's side. It makes every future chirp diagnosis faster, and for CO and combination units the install date approximates when the activation-based end-of-life timer started. Just remember the replacement math for smoke-only units still uses the printed manufacture date, not your handwriting.

Further reading on this site

• Photoelectric vs ionization smoke detectors — which sensor technology catches which fire type, and why NFPA guidance favors coverage of both.
• Where to install smoke detectors — the room-by-room placement rules that pair with the replacement schedule in this guide.
• Carbon monoxide detector requirements by state — the statute-by-statute CO mandate table, including where combo alarms satisfy both requirements.
• Smoke detectors — the full lineup of battery, sealed 10-year, and hardwired units.
• Best smoke detectors 2026 — the current-production picks to replace an expired unit with.
• Best hardwired smoke detector 2026 — interconnectable mains-powered replacements.
• Fire extinguisher ratings explained — the other dated device on your wall; extinguishers from our fire extinguishers collection carry service schedules too.