How often to replace smoke and CO detector batteries
The confusing part is that a "10-year smoke alarm" and a "10-year battery" are not the same claim. The alarm's sensor is rated for about ten years. The battery inside it, on most models, is not — and the two numbers get conflated until someone is standing on a chair during a real emergency, prying at a unit that has been silently dead for a year.
Three different things, three different schedules
1. Test the alarm — monthly
Press the test button. If it chirps or beeps loudly, the sensor and speaker both work. This takes ten seconds per unit and is the only way to catch a dead battery, a disconnected unit, or a sensor failure before you need it. Most people who own a fire extinguisher have never test-fired it; the smoke alarm test button is the equivalent five-second habit that actually matters.
2. Replace the battery — yearly, or the moment it chirps
A single intermittent chirp every 30–60 seconds is the low-battery warning, not a fault — replace the battery immediately, it will not go away on its own. Beyond reacting to chirps, replace non-lithium batteries once a year on a fixed date (many people use a clock-change weekend, since it is already a twice-yearly habit). If your units use a sealed 10-year lithium battery, there is nothing to swap until the whole unit is replaced — check the label to know which type you have.
3. Replace the whole unit — every 10 years
The smoke sensor itself degrades with dust and age regardless of the battery. The manufacture date is printed inside the unit or on the back, not the installation date — a smoke alarm bought "new" at a hardware store can already be a year or two into its life. When in doubt, the date on the unit is the one that counts. Carbon monoxide detectors have their own, usually shorter, rated life — commonly 5–7 years — check the specific label rather than assuming it matches the smoke alarm's ten.
A schedule that actually gets followed
- Monthly — press test on every alarm in the house.
- Yearly — replace batteries in non-sealed units, on a fixed date.
- Every 5–10 years — replace the whole unit, per the date printed on it, CO detectors first.
The monthly test is the one that actually prevents the dangerous outcome — a silent, dead alarm during an actual fire or leak — and it is also the one everyone forgets, because there is no chirp to force the issue and no calendar reminder most people bother to set. It is a five-second task with a large consequence for being skipped, which is exactly the kind of maintenance that benefits from a written-down schedule rather than memory.
Why this belongs on the same list as furnace filters
Like the furnace filter schedule, this is a task with no visible warning until it is overdue by a wide margin, and a real cost to skipping it. Both are also the kind of five-minute job that is trivial to do and trivial to forget, which is the actual failure mode — not that anyone decides not to bother, but that six months quietly become two years.
Keepit puts this on a schedule for you
Set the battery swap and the unit-replacement date once, and Keepit reminds you when each is actually due — no more guessing from a chirp.
Get Keepit on the App Store →