When inspecting a house, I recommend replacing alarms that are 10 years old or ionization alarms with new, photo electric ones. Almost all of the alarms I find are one or the other, or both. You should be able to find the manufacturer date on the back. If you can’t, it most certainly is older than 10 years old.
Photoelectric alarms are less prone to nuisance alarms and respond 30 minutes faster. The cost difference is not significant, and are readily available at the home centers, and 30 minutes is a VERY long time where home fires are concerned. I have read reports of deadly fires where the firefighters found functioning ionization alarms that had not yet sounded. The batteries were still good and the alarm was in the right place.
Replacing smoke alarms is easy and not cost prohibitive. The perfect time to change them is before you move in.
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