re: Shop Air Filter

One more thought...It looks like the fan can be reversed so that it blows inward instead of outward. If you blow the air into the box, it may (?) be a little quieter and it also will collect the dust on the inside which helps prevent it from getting dislodged and fall back into the air.  Another benefit is that in the winter, it will create less of an air flow that might make it a little chilly, especially when standing underneath it.