Edgar, What about the statement below (From RobS' first post)?

"1) “8.1 The unit (including the sensor) shall have a specified lifetime of at least 3 years from the date of manufacture, or from the date the unit is placed into service.â€

This is written such that any detector in the store can be expired before you buy it because it could have been manufactured 3 years ago. does this mean it will beep when you bring it home and, um, plug it in?"

Edgar replies: I don't know, Gert. You could be right.