I know that if I print PLA and stay in the room, it will give me a headache after a while. And I can definitely smell it, so at least something is getting released into the air. I don't know if that actually means it's harmful, but I stopped staying in the same room if a printer is running.
In over a year I've never noticed a smell from PLA during a print.
Maybe that varies between manufacturer, some "PLA" filaments are actually weird mixes (like PLA+).
Agree; with PLA there’s a definite recognisable smell.
Also, when I first got my printer, I had it running in a corner of my office room and found I would reliably get a sore throat after a few hours printing. It’s now shifted to the basement with a extractor fan nearby.