I used to use a box fan in a window, sealed in w/ pillows so no blowback....
I also used to make it very very clear to any who ever asked... never ever fucking do that.
If the electric motor dont spark, the static will, or any other number of simple things....
I guess I just don't see WHY.... do everything else in the shed, step outside for 5mins to fucking blast...
Why ask things like "should I spend the $500 for the right fan" YES. Yes you should. But then if you could do that, why are you open blasting instead of CL, rocking a recovery tank and spark proof system?
This stuff goes boom, don't test way to make it so....