The U.S. Fire Administration gives a home smoke alarm three dates to keep. Test it once a month, put in a new battery at least once a year, and replace the alarm 10 years after it was made. NFPA and the Consumer Product Safety Commission give the same numbers.
Test every alarm once a month
Press and hold the test button until the alarm sounds. Do every alarm in the house, not just the one in the hallway. If your alarms are interconnected, one test should set off all of them, so walk around and listen for each one.
An alarm that stays quiet needs a fresh battery and a second test. If it is still silent, replace it.
Monthly sounds like a lot for something that hangs on the ceiling doing nothing. The reason is simple: a dead alarm looks exactly like a working one, and the button is the only way to tell them apart.
How long smoke alarm batteries last
For an alarm with a battery door, plan on one year. The U.S. Fire Administration says to change a 9-volt battery at least once a year, and the backup battery in a hardwired alarm on the same schedule. Change it on the date, even when the alarm has not chirped yet. Many people tie it to the fall clock change so every alarm gets a battery on the same day.
A low-battery chirp is the alarm asking early. Kidde says its alarms chirp every 30 to 40 seconds (every 60 on some models) for at least seven days once the battery runs low.
Sealed 10-year alarms
Many alarms now come with a lithium battery sealed inside. It is built to last as long as the alarm, so there is no battery to change. You still test it every month. When a sealed alarm chirps, the fix is a new alarm, because the battery cannot come out.
Replace the whole alarm at 10 years
Smoke sensors wear out, and the test button can still work on an alarm that no longer senses smoke well. The U.S. Fire Administration says to replace smoke alarms 10 years from the manufacture date. That date is printed on the back, so take one down and look.
Carbon monoxide alarms run on a different clock. The label gives the life, often 7 to 10 years, and Kidde’s CO alarms start an end-of-life chirp seven years after they were first powered up.
What a chirp means
On an alarm with a replaceable battery, a chirp nearly always means the battery is low. Put in a new one and test.
If a fresh battery does not stop it, check the date on the back. On some models a chirp that a new battery cannot silence is the end-of-life warning, and on others it is a fault. Kidde, for example, uses a chirp every 30 seconds on its sealed alarms to say the alarm is due for replacement. The patterns differ by brand, so the manual (or the sticker on the back) is the place to check.
Where the alarms go
The U.S. Fire Administration asks for an alarm inside each bedroom, one outside each sleeping area, and one on every level of the home. It also recommends interconnected alarms, so that when one sounds they all do.
Keeping track of the dates
The monthly test is the one that slips. Househand, our home maintenance app, has all three jobs on its starting schedule: a test of the smoke and carbon monoxide alarms every month, new batteries once a year in November, and a reminder to replace the alarms at 10 years. Each one names the U.S. Fire Administration as its source and has a page of its own. If your alarms are sealed, switch the battery job off. With reminders on, one arrives on the morning a job falls due. It is free on the App Store and Google Play.
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The other yearly job people ask about is the water heater. We covered it in how often to flush a tankless water heater.
Frequently asked questions
How often should I check my smoke alarm?
Once a month. Press and hold the test button until it sounds. The U.S. Fire Administration, NFPA and the Consumer Product Safety Commission all give the same monthly interval, and it applies to sealed 10-year alarms as well as ones with a battery door.
How long do smoke alarm batteries last?
Plan on one year for a replaceable battery. The U.S. Fire Administration says to change it at least once a year, even if the alarm hasn't chirped. A sealed lithium battery is built to last the life of the alarm, which is 10 years, and you can't change it.
Why does my smoke alarm chirp at night?
Usually a low battery. Kidde, which makes alarms, says a weak battery struggles more as a room cools, and most homes are coolest between 2 and 6 a.m., so that's when it starts chirping. Change the battery and test the alarm. If a sealed alarm chirps, replace the alarm.
Do hardwired smoke alarms need new batteries?
Most do. A hardwired alarm runs on house power but has a backup battery for outages, and the U.S. Fire Administration says to change that backup once a year too. Some hardwired models have a sealed backup that lasts the life of the alarm.
When should I replace a smoke alarm?
Ten years from the date of manufacture printed on the back, not from the day you bought it. Carbon monoxide alarms have their own limit on the label, often 7 to 10 years.