How to Replace Smoke Alarms That Are More Than 10 Years Old

Fire Prevention Week runs October 4 to 10, 2026, and it is the one week a year most people look up at the alarm on the ceiling. The wrong assumption is that an alarm that passes the test button is fine. The sensor inside wears out, and the US Fire Administration says the whole unit has to be replaced 10 years from the date it was made, whether it runs on a battery or is wired into the house. Checking every alarm takes one afternoon and a step stool.

Take each alarm down and read the date on the back

Twist the alarm counterclockwise off its mounting plate. On a hardwired unit, unplug the small wiring connector too. The manufacture date is printed or stamped on the back, usually near the model number. If that date is more than 10 years ago, or there is no date at all, the alarm is due for replacement no matter how it sounds. Write down how many alarms failed the check and whether each one is battery powered or hardwired, then put the ones that passed back up.

Count where alarms belong before you shop

The US Fire Administration's list is short: one alarm inside each bedroom or sleeping area, one outside each sleeping area, and at least one on every level of the home. Walk the house and count. Most older homes are missing at least one bedroom alarm. Add the missing spots to the replacement count so you buy everything in one trip.

Choose sealed or replaceable battery units, and match hardwired to hardwired

If the old alarm was hardwired, buy a hardwired replacement with a backup battery so the alarms still sound in a power outage. Where you can, choose interconnected alarms, which means that when one sounds they all sound. For battery-only spots there are two kinds. A sealed 10-year lithium alarm never needs a battery change and is replaced as a whole unit when the manufacturer says so. A 9-volt battery alarm is cheaper but needs a fresh battery at least once a year. Buy whichever you will actually maintain.

Mount the new alarms and mark the replacement year

Screw the new mounting plate into the old holes, connect the wiring on hardwired units, twist the alarm on, and press the test button until it sounds. Before you climb down, write the install date and the year it will be 10 years old on the side of the alarm with a permanent marker so the next check takes seconds.

Test monthly and put the battery change on the calendar

Press and hold the test button on every alarm once a month until it sounds. On 9-volt models and on hardwired models with a backup battery, change the battery at least once a year. Put both on a phone calendar now, while the ladder is out.

If that fails. An alarm that will not sound on the test button after a fresh battery is dead. Replace it regardless of the date on the back.

If someone in the house is deaf or hard of hearing. The US Fire Administration lists alarms that flash a strobe light or vibrate to wake someone who cannot hear a standard alarm. Put one in that person's bedroom.

Sources. US Fire Administration, Smoke Alarms, NFPA Fire Prevention Week.