How Often Should You Replace Smoke and Carbon Monoxide Detectors?

Smoke detectors: every 10 years

This is the standard guidance from fire safety organizations, regardless of whether the unit still passes a test-button check. The sensors degrade over time in ways that a test button doesn't fully reveal. The manufacture date is printed on the back of most units — check it directly rather than guessing based on when you moved in.

Carbon monoxide detectors: every 5 to 7 years

CO sensors have a shorter effective lifespan than smoke sensors. Check your specific unit's manual, since this varies more by model than smoke detectors do.

Batteries: don't wait for the low-battery chirp

For battery-powered units, replace batteries at least once a year — many people tie this to a specific date they'll remember, like a clock change. For hardwired units with battery backup, the backup battery still needs the same annual attention.

Placement matters as much as age

• Smoke detectors: inside every bedroom, outside each sleeping area, and on every level of the home, including basements
• CO detectors: near sleeping areas at minimum, and on every level if you have fuel-burning appliances or an attached garage

Test monthly

Pressing the test button once a month takes seconds and confirms the alarm itself still sounds, independent of whether the sensor is still accurate — both checks matter.