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.
I think air scrubbers are for more intensive situations, like cleaning a flood damaged home, or painting things, since they’ve got chemical filters and UV sterilizers in them. Air washers are mostly just air filters that rely on water to trap stuff first and foremost, one I saw was just a series of spinning disk’s half submerged in water. Surface tension caused water to stick to the disks, and a fan blew air between them, so anything in the air would get caught and pulled down into the water tray.
The other function they serve is passive humidifiers, as air passes over the water it evaporates, but only if the air is capable of holding the water. If it’s already humid no evaporation occurs, so you don’t get things like condensation that you’ll see with active humidifiers that aerosolise water.
You can diy one by hanging up a towel, having the bottom touching a container of water, and pointing a fan at it, and capillary action will draw the water up into the towel. So with one of these boxes with cotton filters, would serve the same purpose.
I’m not sure I would call the humidification passive given the action of the fan, but yes, in the limit it will push to 100% humidity. One thing to note with that kind of setup is that mildew/mold can quickly build up in the unit and, if it keeps the ambient humidity high enough, in the dwelling. So, it can just trade one air quality issue for another. Buildup in the unit can be prevented by adding a small amount of biocide to the water (formulations for humidifiers are usually alkonium salts). However, it well eventually encrust the wick and force replacement or washing (wear gloves).
Ohhh ok that’s fascinating