Smoke Detector Expiration Date Calculator
Smoke alarms are rated for 10 years from the date of manufacture — CO alarms for as little as 5. That date is printed on the unit, but every brand hides it differently. Pick your detector type and brand, find the date with the guidance below, and get an honest replace-by date — then build a printable schedule for the whole house. Everything runs in your browser — nothing is uploaded.
Your detector
Result
The replace-by date printed on the unit itself overrides everything shown here — these are typical rated lives, and models vary. This tool can never tell you an alarm is safe: whatever its age, test it monthly with the test button, replace non-sealed batteries at least yearly, and replace any unit that fails a test or has no readable date.
Whole-home replacement schedule
Walk the house with a step stool: for each alarm, set its type and manufacture date above, name its location here, and add it. Print the finished schedule and keep it with the fuse box.
No detectors added yet — add each alarm in your home to build the schedule.
| Location | Type | Made | Replace by (earliest) | Status | Remove |
|---|
Sorted soonest-first. The replace-by date printed on each unit overrides this schedule; test every alarm monthly.
Why do smoke detectors expire?
The sensors degrade. A smoke alarm's sensing chamber slowly loses sensitivity with dust, humidity, and age, which is why NFPA 72 calls for replacing smoke alarms 10 years from the date of manufacture — even hardwired ones, even sealed 10-year-battery models (the 10 years runs from manufacture, not installation). CO alarms are stricter still: their electrochemical sensors are only precise for about 5–7 years depending on the model era, so combination smoke/CO units are limited by the shorter CO life.
Where is the date on my alarm?
Twist the unit off its mounting bracket and look at the back label — since 1999, UL has required the manufacture date there in plain English. Depending on brand and age it may be a plain date ("2019 JAN 15"), a year-month-day code ("2017JUN09" on USI units), or an explicit "replace by" date on the side of newer sealed Kidde and First Alert models. If your unit shows a printed replace-by date, use that — it overrides the typical figures here.
What if there's no readable date at all?
A unit with no plain-English date on the back almost certainly predates the 1999 UL labeling requirement, which makes it well past any rated life. Don't try to decode it — replace it.
Is this official guidance?
No. This tool summarizes typical, publicly stated rated lives by detector type; exact lifespans vary by model. It is not safety advice and never certifies an alarm. For authoritative guidance on smoke alarm placement, testing, and replacement, see NFPA's smoke alarm resources, and check your unit's label or the manufacturer's support pages for your exact model.
Does my data get uploaded?
No. The page is fully client-side; nothing you enter leaves your browser.