[BobnBev]

Originally Posted by villagetinker

IMHO, if you are getting the 3 beep pattern (indicates a problem with the sensor and needs to be replaced) I would replace ALL of the smoke detectors at the same time. My reasoning, they are all the same age, and will probably all fail around the same time, I would rather do this once every 7 years or so than have to replace individual alarms over a 1 or so. Also, there are CO2 at the bedrooms, these need to be replaced by CO2 detectors according to building codes. Lowe's has a builders pack of smoke detectors that saves a few dollars over buying separate units. The CO2 units cost more than twice as much as plain smoke detectors. If you take one unit off and take it to Lowe's they can match with exact units which make replacement a breeze.
Hope this helps.

Same with ACE Hardware. We did all of ours when we moved in. I think the FD recommends every 10 years.