Thanks for your concern. I already know I would need a pull chain unless I really wanted to delve into electrical work, which I don't. I don't dig in that closet often, but hate that I have to get a flashlight when I do.
Even when I was trying to find replacement hardwired units, I read all the pros and cons for wired and battery operated. Wired means they all go off at once, but not at all if the power goes out. Know what I mean? I can only assume these are original installs from 1982. They "work" in that shower steam will set them off, but a recent smokey oven fire did not (I don't want to talk about it). They are useless.
There are all kinds of codes for rental properties here, but none for owners. The only requirement is from my insurance company that I must have both smoke and CO detectors, and they don't care which kind. A firefighter friend of mine years ago gave me battery operated detectors for Christmas (also close to 1982, as I recall those years). Aw! So sentimental!
Anything is better than nothing, he said, and nothing is what I have now, as far as I'm concerned.
So fear not! I will have a smoke and fire alert system in my house no matter what. I just want to use some established wiring for a few more lights, thank you.