A way to say "ciggarette break" without your boss knowing that you're going to have a smoke. Especially useful in non-smoking environments. The term "fresh air" can also be used to mean "ciggarette" but is not typically necessary and doesn't sound right in most contexts.
Employee 1: I'm going out for a fresh air break
Boss: Ok, just be back in 15
Employee 2: (whisper) He doesn't know you mean you're going for a smoke?
Employee 1: (whisper) No! That's the point!