Another Zoshchenko question

[kutsuwamushi.livejournal.com]

Now I'm reading "Кошка и люди" and have a question about this sentence:

Вскоре стал, конечно, угар по комнате проноситься.

Maybe it's obvious and I'll feel stupid for asking ... but why is this in the infinitive?

I'm assuming that it's the fumes that are moving around the room because of the way the sentence is constructed, but if that was the case I'd expect it to be in the past or present tense, not in the infinitive.

Edit: Thank you! I understand it now. For some reason I thought "стал" was referring to one of the characters suddenly standing up, but it makes complete sense if it's not. :P