DICheck the date, not the light
How to Find a Smoke or CO Detector Expiration Date
The indicator light can show power without telling you the age of the sensor. The date label on the alarm is the dependable starting point.
Look on the back or side
Many alarms print a manufacture date, install-by date or replace-by date on the back. If the unit must be removed to read it, use a safe ladder position and follow the manufacturer’s removal instructions.
Smoke alarms: ten years
Replace smoke alarms at ten years unless the manufacturer or a defect requires earlier replacement. Write the planned replacement year where it can be found without dismantling the unit next time.
CO alarms: follow the model
CO sensor life varies, often within a five-to-ten-year range. Use the replace-by marking or instructions for the specific model rather than applying the smoke-alarm rule automatically.
Build a household inventory
Record location, alarm type, model, manufacture date and replace-by year for every unit. Detector Inspectors can create this whole-home picture during a service visit.
Safety references
Primary sources used for this page:
- NFPA smoke-alarm safety guidance
- U.S. CPSC fire-safety guidance
- U.S. CPSC carbon-monoxide alarm guidance
Manufacturer instructions and current local requirements control. For an emergency, call 911.