With the recent wildfires and the gestures broadly at the world I just wanted to share this link to the Corsi-Rosenthal Box. A simple homemade air filter that can be made with a box fan or several computer fans using off the shelf merv 13 or higher filters from your local store.
Yes, these have existed since before COVID. I had someone elsewhere get made at me because “it shouldn’t be named that! Those two didn’t invent it!” but like, I didn’t choose the name lol. Anyways, I’ve made two for my house (former hoarder house we inherited and we haven’t had the ducts cleaned yet but everything else is clean) and I can say, we both sleep better at night and they worked great through the wild fires.
Anyways, just wanted to share this as a quick little easy project. Or you know, not so quick if you wanna be like the people on Reddit’s r/CRBoxes who 3D print fancy housings and do elaborate computer fan builds. Whichever you prefer.
Edit to add: Someone posted a Build Guide (non Reddit link) on Reddit for making boxes with PC fans.
I know we don’t love Reddit links but
- Here’s a Reddit post for a DIY/buy guide
- An Information post
- A tall computer fan box
- Triangle box fan
Sorry for the Reddit links, they just have a lot of conversations going on there currently.
There are alternate builds https://cleanaircrew.org/box-fan-filters/.
In past years, I’ve built one with only one filter that the fan pulls through. You need to offset the filter from the face of the fan still by 8" or so with a cardboard spacer to help it be more efficient. It worked.
I’ve also built one with two filters in a triangle configuration, that one worked well too.
This is the first year that I’ve built one that is actually a cube with 4 filters. They all work, the 4 filter one works the best, but it also takes up the most space.
I also built one, and I attached charcoal filters to it, which has significantly reduced the amount of dust in my house, and the air generally smells not at all.
The previous owners of my house were dog owners, so if I don’t run it for a while, then there’s like a hint of dog odor that even replacing all of the carpet and flooring in the entire house and running an ozone machine on workdays for a week has not gotten rid of.
But as long as the fan is running, that odor is taken care of.