https://s3-us-west-1.amazonaws.com/hmt-forum/corsi_rosenthal_box.jpg
I have seen a few of these builds before, take 4 furnace filters that fit around the box fan (making a 3D box, put the fan on top so it sucks stuff into the box and blows out the top, and presto, a mini HEPA like filter system. Cool build and cheap.
https://www.homemadetools.net/forum/coronavirus-homemade-tools-78415-15#post200198