I put this together a while ago and it works so well, I thought I should share it.
I have a basement shop with not a lot of height so I really don’t have room to hang a filter from the ceiling. I built this unit up against one of the windows so when I want to use it as a filter only, I keep the window closed and the sliding doors open. If I’m finishing, I just open the window and close the sliding doors. It takes a 14X20X1 furnace filter. I have my table that I use for sanding very close to the filter and it is amazing how fast the filter gets dirty. My shop is pretty well isolated from the rest of the basement with insulated walls and ceiling and separate heat so the dust is kept in the shop. The only thing I may change would be to change the blower to a forward curve (squirrel cage) to cut down on the noise but when I’m sanding I have the muffs on anyway. I have a vent installed in the other end of the shop to let in fresh air through another window for finishing.