According to NFPA 72, smoke detectors in one- and two-family dwellings must be replaced every 10 years.

• A. Every 5 years
• B. Every 7 years
• C. Every 10 years
• D. Every 15 years

Answer: (C)

Smoke alarms have a limited service life, and NFPA 72 sets a 10-year replacement interval for units in one- and two-family homes. Replacing the entire unit after ten years keeps detection reliable, because sensor components age, dust and other contaminants can affect performance, and simply changing batteries doesn’t restore original sensitivity. When checking, look for the manufacture date on the back or side of the detector; if it’s older than ten years, replace it. If you have a sealed 10-year battery model, you still replace the whole unit at the ten-year mark. This interval isn’t matched by shorter or longer timelines like five, seven, or fifteen years.