Holy fuck
This works best if you keep windows closed.
Another design is using 2 20x25x1 filters, taping them to the sides of the box fan and then to each other so they sort of make a triangle, then cutting cardboard to make a top and bottom to the triangle.
This was discovered as a more effective design during the 2020 US west coast fires.
https://tombuildsstuff.blogspot.com/2013/06/better-box-fan-air-purifier.html
Better Box Fan Air Purifier A better more efficient and odor eliminating homemade air purifier than just taping a 20x20x1 filter to a box fan. Sometimes you need to tombuildsstuff.blogspot.comIf you live on the west coast of the United States, fire season is coming and this is vital.
We’ve been using one, and they’re great. Might try to make the double filter version this year.
theyve been doing a bunch of studies on this during the pandemic and this design is best! 4 filters and a shroud to optimize flow rate.
Corsi-Rosenthal Cube Corsi-Rosenthal Cube encycla.com