Life-safety devices · Smoke alarm
How long do smoke detectors last?
This is the one part of a house where the answer is a date rather than a range, and it is the makers and the fire-code people who print it: NFPA calls for every smoke alarm to be replaced 10 years after the manufacturing date on its back label, and Kidde builds the same ten years into the alarm — its sealed-battery models switch to an end-of-unit-life chirp ten years after first power-up. The warranty on those models also runs ten years. Warranty and service life landing in the same year is rare on this site, and they are still not the same promise.
Updated
The gap: warranty ends at 10 years; typical service life ends around 10 years. The paper and the typical service life end together — an unusually honest term. Warranty document (Kidde, checked 2026-08-27)
Typical service life: 8–10 years
NFPA's phrasing is flat: "All smoke alarms must be replaced 10 years after its manufacturing date." Kidde's own timer runs on a different clock — "Ten (10) years after the unit was installed, powered up, and tested, this unit will automatically alert you that it is time to replace the unit" — so an alarm that sat in a box for a year or two before it went on the ceiling reaches NFPA's replace-by date well before it ever chirps about it. The 10 is the figure both NFPA and the makers print; the 8 only bounds the drawing for that shelf gap. InterNACHI's undated baseline chart is more cautious still, listing smoke and heat detectors at "less than 10" years.
Tier 2 · trade / standards literature Range from NFPA — Learn More About Smoke Alarms, checked 2026-08-27.
Smoke alarms are rated for finished living space and nothing else. Kidde's operating band for the 20SD10 is 40°F to 100°F and up to 95% relative humidity non-condensing, which is why garages, unfinished attics and crawl spaces are named as places not to mount one: cold, damp and dusty air both shortens the sensor's working life and multiplies the nuisance alarms that get an alarm taken down and never put back.
What the warranty paper actually says
Kidde (Photoelectric Smoke Alarm Model 20SD10 (sealed 10-year lithium battery)) publishes a 10-year limited, conditional warranty. Kidde warrants the alarm free from defects in material, workmanship or design for ten years from the date of purchase, and its obligation stops there: repair or part replacement only, no installation, after you ship the alarm postage-prepaid with proof of purchase to its warranty department in Mebane, North Carolina. It does not apply if the alarm was damaged, modified, abused or altered after purchase, or if it fails through improper maintenance or inadequate power — and Kidde states separately that removing the alarm's back cover voids it. What the ten years does not cover is the thing that actually ends the alarm: reaching end-of-unit-life on schedule is the alarm doing what the same manual says it will do, not a defect.
The warranty document itself , checked 2026-08-27.
What shortens it
- Shelf time before installation — NFPA's ten years runs from the manufacturing date on the back label, not from the day the alarm went up
- Dust and insects in the sensing chamber, which is why every manual carries a cleaning section; Kidde's guide warns outright against dusty locations
- Paint, stickers or other decorations over the alarm, which NFPA says could keep it from working
- Kitchen and garage placement: Kidde's guide says not to mount within 6 feet of cooking or heating appliances, and not in a garage, where starting a car puts products of combustion in the air
- Temperature and humidity outside the rated indoor band — Kidde gives 40°F to 100°F and up to 95% RH non-condensing, which rules out unfinished attics and unheated garages
- Drafts: NFPA says not to install alarms near windows, doors or ducts, where air movement can interfere with them
- Opening a sealed ten-year unit — Kidde says removing the back cover voids the warranty, and the battery in these models is not meant to come out
Signs of wear to look for
- A manufacturing date on the back label ten or more years old — the date NFPA counts from
- Chirping that continues after a fresh battery, which NFPA says means the alarm is at the end of its life and the unit must be replaced
- No sound when the test button is pressed; NFPA's instruction is to change the battery, or replace the whole unit if it is over ten years old
- On Kidde's self-testing models, an amber LED with three chirps a minute — the manual's smoke-sensor fault and fatal-fault signals, both of which end in replacing the unit
- Nuisance alarms from a unit that never used to do it, often the first outward sign of a dirty or aging chamber
- Yellowed or cracked housing, or a loose mount that lets the alarm hang away from the ceiling
- An interconnected set where one alarm sounds and the others stay quiet — NFPA warns that mixing manufacturers can leave alarms unable to trigger each other
How many alarms a home needs and where they belong is set by NFPA 72, the National Fire Alarm and Signaling Code, which for many years has required an alarm inside every sleep room, outside each sleeping area and on every level — and whether existing wiring can carry an interconnected set is a separate matter again. Both are questions for the fire service or a qualified inspector; that is an inspection question, not a web-page question.
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