How to Find a Smoke or CO Detector Expiration Date

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.