ok , very brief pics from a long time ago project ..
Fan is from am old VW Polo car
Air filter and pre-filter is from axminster
fan surround is cut down with a jig saw and metal blade and fitted into a basic frame
seal on the back with anything you have in your "use one day" stash ! lol
Carful with a nail gun .. it doesn't come out the side !
the main box is so simple .. doesn't matter what "joinery" you use
Some weather strip before I drop the filters in
I added a bit of plastic gauze over the front so I could shop vac the pre filter easily
Here it is fitted up to the top .. in the only easy place I had for it.
the Car fan runs of a cheap battery charger
the air clears quickly, and the filters need cleaning regularly.. so it must be working ! :-)
Cheap as chips :-)