Smoke Detector?

Inspected a home (remodeled in 2005) today and all the detectors made a low beep sound not the normal loud alarm sound. I was thinking low battery but they were not chirping. Are they bad detector?

Did you notice if breaker was in Off position? Or was power recently restored?

All breaker were on at the time…checked.

It sounds like the back up batteries could be the problem. I would suggest replacing the back up batteries as a start. But keep in mind that the USFA recommends replacing detectors after 10 years (even hard wired ones). If they were installed in 2005 (9 years ago) and is not acting normally, I would not hesitate at suggesting replacement.

Why not just list them as defective or non operational and recommend further evaluation and repair or replacement?