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
correct me if I'm wrong but anything higher than MERV 13 has diminishing returns because of increased resistance. instead of going for increased MERV I recommend getting thicker MERV 13 because of their bigger surface area.
CR boxes rely on raw total air volume and increased ACH vs HEPA which relies on filtering as much air as possible on the first pass.
If you go for the 2” thick filters they breathe better and have more surface area.
this is true. I pick up filters from shut down businesses and warehouses sometimes when people dont know what they cost and post them to fbm or craigslist and if they are higher than 13 I also put a filter for the bottom panel since I usually hang them blowing down with cords taped at the corners. even then they start to suck inward.