It's done by one of our fellow forum members here ( @guilhermecn ). There you go:
https://www.youtube.com/watch?v=qYVe47uXcwA
There were one or two other interviews that he talked about this (which included the smoke bit), but it would take too much time for me to find them, so I'm sorry for not being able to provide them.
But I thought the whole appeal of PhysX is to add additional graphical effects? Then what is the point of PhysX being enabled in the game? I don't get it.