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
- MERV explained by the EPA (not a Reddit link) than you OatScoop
Sorry for the Reddit links, they just have a lot of conversations going on there currently.
More on filters:
Most HVAC filters are designed to keep the system clean enough to avoid problems – they aren’t for purifying air, they’re to keep gunk from building up on equipment and ducts. Using a higher rated filter in a system that wasn’t designed for it will cause expensive problems down the road. The restricted airflow (which only gets worse as the filter gets clogged) is hell on the equipment: it’s less efficient and can’t exchange heat at the rate it was designed to. E.g.
Unless your HVAC system was purposefully designed to act as an air purified (and you’re following the manufacture’s directions) you’re better off using a “low efficiency” filter for it and purifying the air with purpose build devices … like a Corsi-Rosenthal box.