I recently stayed in an apartment that didnt have central air so I created a corsi-rosenthal box since the smoke from the Canadian wildfires were so bad.
After 30 days of continuous use, with very minimal periods of it being turned off, this is what the filters look like!
It's disgusting yet also so satisfying to see the filters get darker from debris, dust, and dirt.
Edit: typos
What you see are 4 hepa filter plates taped together into a box, with a fan on top. The fan blows air upwards, thus creating a low pressure environment inside the box, which sucks the air through the filters - which are originally starch white.
Yep and if you want to get really fancy, ya can put the box on stilts and put a 5th filter on the bottom!