for those who live in an apt. are there smoke detectors and/or carbon monoxide detectors in any or all the units? If so, do they come around and change the batteries every 6 months or so like they do in our complex?

When we lived in an apartment many years ago, they didn't even have smoke detectors. But in the apartment my niece lives in, the smoke detectors are wired into the electrical system with a battery back-up, she says they change the batteries once a year.

The apartment I lived in New York City was lacking in a lot of things, but the smoke detectors we had were hard wired into the electricity, so there were no wires to change!
Almost made up for the ridiculous rent they charged!

;)

We live in our condo. It has smoke detectors built into the ceilings. They're maintained externally. No carbon minoxide detector.