Guys, Why would be breathe heavily around me?

So there is a guy who I have been crushing on for some time now, who has been crushing on me as well. Today as he walked by me closely he kind of breathed heavily in/out, it was a bit weird, but it was almost like he was breathing in my scent or something. I know that sounds crazy/weird but I don't really know how else to describe it. He always gets close to me, but this is the first time he breathed heavily around me. We are still kinda shy as its only been a few months we know each other.

Guys, Why would be breathe heavily around me?
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