This fan sits in a window at the top of the stairs leading up to my cigar room. It sucks air in and blows the smoke out of the window in the room. I've been reading for a while now that putting a shroud on a box fan will increase its airflow and reduce the noise it makes by preventing the turbulence in the corners - round spinning blades in a square box; the air wants to circle back around to get sucked through again, is how I'd put it. I chose to use four pieces, rather than find one big piece and cut a hole in it. We'll see how it works this afternoon when I get lit.