Required in bedrooms here to be on AFCI & off a lighting circuit (or possibly another circuit that usually will not be shut off
And that means a breaker, which means all of my smokes/CO's are on AFCI
"Recent editions of NFPA 70 have required that all 120 volt outlets in bedrooms, which includes 120 volt powered smoke alarms, be protected by an AFCI.
Every smoke I have has (& is required) to have abattery backup
With the number of smokes required I can hear one going off anywhre in the house
I actually woke up in the night to the sound of the chirp from the basement smoke when the battery went