Saw someone on Facebook say the built one of these. Looks like an interesting project! | DIY box fan filters – Corsi-Rosenthal box - Clean Air Crew https://cleanaircrew.org/box-fan-filters/ "Also known as a Corsi-Rosenthal box, this DIY method of building your own air filter with MERV13 furnace filters and a box fan are an easy and cost-effective way to help clear indoor air from airborne virus particles, wildfire smoke, pollen, dust, and more!"