There’s no need for 2" filters. 1" works fine to filter a large room with the standard box fan in several minutes. That’s also what the standard guide recommends. Couple of days ago at the peak smoke in Toronto it got the PM2.5 from 50 to 0 in under 10 minutes.
Here’s the standard Corsi-Rosenthal box instrucrions: https://corsirosenthalfoundation.org/instructions/
There’s no need for 2" filters. 1" works fine to filter a large room with the standard box fan in several minutes. That’s also what the standard guide recommends. Couple of days ago at the peak smoke in Toronto it got the PM2.5 from 50 to 0 in under 10 minutes.
Lemmy hugged the site to death, but archive.org has some snapshots.
https://web.archive.org/web/20260517182405/https://corsirosenthalfoundation.org/instructions/