Can Hardwired Smoke Alarms beep without power?
Yes if you remove all power it can beep a few times from stored energy in the detector.  But not 8 years.  8 seconds, maybe.  I never heard of the fire code ever allowing &quot;plug in&quot; smoke detectors, though.  They are supposed to be permanently mounted (or rather mounted well enough to be difficult for the average conehead to mess with.)