If staffers complain a co-worker smells bad, your best bet is to confront the person in private.
But what to say?
Try this: This is difficult to say, so I want to make it as straightforward as possible: I believe you may have a problem with (bad breath or body odor). I’m concerned it’s having an impact on your ability to interact with your co-workers.”
Another phrase that can soften the blow: “If it was me, I’d want to know.”