How often should you replace your smoke and CO detector units?

This task protects people, not just the house. Do it on a schedule to make sure it gets done.

Staying on schedule matters beyond the repair bill: a consistent maintenance record is one of the factors in a home's Roots Home Health Score, and well-kept homes typically sell faster and closer to asking price.

How to do it

The sensors inside detectors wear out even if the unit still powers on: smoke sensors at about 10 years, CO sensors at 5–10. Past that, a detector can pass the button test while being blind to the real thing.

1. Check the manufacture date printed on the back of each unit.
2. Replace smoke alarms at 10 years and CO alarms per the model's rating (usually 5–10 years), regardless of how they test.
3. Match placement to code: alarms in every bedroom, outside sleeping areas, and on every level.
4. Consider interconnected units so one alarm sounds them all.

Alternatives & optional extras

• Combination smoke-and-CO units with a sealed 10-year battery simplify the whole system to one replacement date.
• Interconnected (wired or wireless) alarms are worth it in larger or multi-story homes so you hear a basement alarm upstairs.

Time: 30 minutes · Typical cost: $15–$50 per unit

What you'll need

• Combination smoke + CO detector (10-year sealed battery)

If you skip it

An expired sensor can test fine yet fail to detect real smoke or CO, giving a false sense of safety exactly when it matters.

Other smoke & co detectors maintenance

• Test smoke and CO detectors — once a month
• Replace smoke detector batteries — once a year

Related systems to keep on schedule

• Fire extinguisher — start with: check fire extinguisher gauge and condition, once a year
• Security system — start with: test security system and camera batteries, every 6 months