Smoke alarms do not last indefinitely. As a general benchmark, U.S. fire-safety guidance calls for replacing an alarm when it reaches 10 years old unless the manufacturer specifies an earlier interval; the unit's manufacturing date is more useful than remembering when its battery was last changed.
Find the manufacturing date on the alarm
Remove the unit from its base according to the manual and look for a date printed on the back or side. If it is 10 years old or more, or the manufacturer gives an earlier end-of-life date, replace the entire alarm.
A new battery does not reset sensor age
Changing a replaceable battery restores power, but sensors and electronics also age. A ten-year-old alarm with a new battery is still an alarm at the usual end of its replacement interval.
Sealed-battery alarms are also replaced as complete units
A long-life sealed battery is designed to match the alarm's service life, not make it permanent. When the end-of-life signal occurs or the specified age is reached, replace the whole alarm.
Test regularly and replace sooner if it fails
Use the test button at the interval specified by the manufacturer and local rules. An alarm that does not respond after power is checked, is physically damaged, or gives an end-of-life signal should be replaced without waiting for its tenth anniversary.
Sources
- U.S. Consumer Product Safety Commission — Fire Safety — Home-fire prevention and warning signs requiring immediate action.