I've heard conflicting advice whether smoke detectors should be on a simple over-current breaker or a AFCI/GFCI breaker. On one hand you want the circuit to be as reliable as possible and since there will be nothing additional plugged into the circuit a simple over-current breaker makes sense. On the other hand the 2017 code requires just about all 120 volt circuits to be protected at the panel (new construction) with at least AFCI. 2020 code seems to require everything from the doorbell on up to the range to be GFCI protected and most 120 v circuits to be AFCI protected as well.
I'm really curious because I just installed the smokes for my sons new house and the instructions said they should not be on a GFCI/AFCI protected circuit. It passed final electrical inspection today and the smokes were on an AFCI breaker.
Thoughts from others here?