Test monthly, replace every 10 years
Press the test button on every alarm once a month. Replace standard batteries at least once a year. Replace smoke alarms 10 years from the manufacture date printed on the back, and CO detectors on the schedule the manufacturer prints on the unit, often 5 to 7 years.
Working smoke alarms roughly halve the risk of dying in a home fire, and carbon monoxide is colorless and odorless, so a detector is the only warning you get. Both are only useful if they actually work when the moment comes, and both fail silently as they age.
The rhythm is simple once you know it: test monthly, batteries yearly, whole units on a decade for smoke and sooner for CO. The date that matters is the manufacture date stamped on the back, not the day you put it up.
How to do it
- Once a month, press and hold each alarm's test button until it sounds, usually a few seconds. If it does not sound, replace the battery and test again; if it still fails, replace the unit.
- Replace batteries in battery-powered units at least once a year. Tying it to a fixed date, like a daylight-saving change, makes it easy to remember.
- Never pull a battery from an alarm to use elsewhere and leave the alarm dead.
- Check the manufacture date printed on the back of each alarm.
- Replace any smoke alarm that is 10 or more years past its manufacture date. The sensor degrades even if the unit still beeps on test.
- Replace CO detectors on the service life printed on the unit, commonly 5 to 7 years. An end-of-life chirp or an 'End' display means replace the whole unit, not the battery.
- Confirm placement: a smoke alarm on every level, inside each bedroom, and outside each sleeping area; CO detectors on every level and outside sleeping areas.
- Vacuum dust from the vents once a year so buildup does not dull the sensor.
Common mistakes
- Pulling a battery to stop a nuisance alarm and forgetting to put it back. That leaves the home unprotected.
- Replacing the battery on a 10-year-old alarm instead of the alarm. A fresh battery does not restore a worn-out sensor.
- Mistaking the CO end-of-life chirp for a low battery. The end-of-life signal means the detector has expired and must be replaced.
This is exactly the kind of thing that is easy to know and easy to forget. Adulting can put it on a cadence so it surfaces when it is next due, instead of when something goes wrong. Free to start.
Sources
Questions people ask
- Why replace an alarm that still works?
- Smoke sensors degrade with age and are much likelier to miss a real fire past 10 years. The test button only confirms the horn and battery, not the sensor's ability to detect smoke.
- Do sealed 10-year-battery alarms still need testing?
- Yes. Test them monthly like any other alarm. They just skip the annual battery change, and you replace the entire unit at the end of its life.