[PDF] https://aghealth.ucdavis.edu/sites/g/files/dgvnsk261/files/i...

     Materials:
     (1) 20” x 20” box fan
     (4) 20” x 20” x 2” furnace filters MERV-13 / Filtrete™ MPR 1900
     (1) fan shroud made of fan box
     (1) fan bottom made of fan box
     Duct Tape (lots and lots)

> This device with the right fan can deliver 600 to 800 cubic feet per minute.

> And the cost of all the materials for doing this is on the order of about $65.

> So about one-quarter of the cost of a really good HEPA air cleaner to build a Corsi-Rosenthal box, which is more effective than that much more expensive air cleaner.