[Speedslug]

I got the fan from my own house furnace when it got replaced and then I stumbled on to a 6 foot by 3 foot kitchen hood for free on Craig's List.

I mounted the fan on the hood and hung that from the ceiling with chains and springs to keep the noise from getting transferred to the ceiling and turning that into a sounding board and amplifying the noise.

I got an 8 inch "blast gate" (kind of like a guillotine) that I rigged a frame around so I could add a pulley and flex wire to which allows me to pull it up and down to keep the Minnesota cold out.

If you are doing minus 40 you might have to get two blast gates and even then you may need to modify them for a tighter fit.

As for make up air in the winter, I have my torch bench against a window so I can pull cold air from the window to travel with the torch fumes and limit how much of the heated house air goes up the fan.

I do move about 5 % of the flow from the heated air over my shoulder so I don't wind up with a face full of fumes.

Good Luck.