A person, usually on a construction site, who refuses to dress warmly in cold weather, and will only wear a t-shirt year round.
* Rusty walks by in a t shirt in -5 degree weather *
Mike: Hey, did you see rusty walk by in a t-shirt?
Lyle: Ya, I geuss he's the last of the fresh air boys
This can also can be used as a question to make fun of someone under-dressed...
* Two Dummies walks by in t-shirts *
Darren: Oh, you like that fresh air, boys?