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.
In my area, we have annual fires that get pretty bad. Add in ag related pollution, allergies, etc…and air quality is almost always unhealthy.
Our local makerspace has partnered up with our local asthma collaborative to make custom PM sensors here: https://www.sjvair.com/ (code is here: https://github.com/sjvair)
We have tried out a couple of designs and had actual science done on which custom air purifiers did the best. One of the members rigged up a airtight area and pushed smoke in. Got a couple of readings, then did the same test with the air purifier designs. I think we tested close to 10 different designs including some air purifiers you get from local stores.
We found a couple that work well.
https://github.com/opennukit/Nukit-Open-Air-Purifier/ is a good one.
The local makerspace did some work and found a design that worked well. It was 2nd best at air purification but was super cheap.
One that we improvised was the following:
3d printed brackets, a filter, and some activated carbon and you have a good air purifier. Family uses these for white noise and air purification at night. It works wonders! The fan is 20$ at any wallmart, the filters are dirt cheap. And you can get huge rolls of activated carbon on amazon. No need to over complicate things, just bracket everything on, let it sit for a good 3-4 months, then look and see if anything needs replacing.
One note of caution, some of the huge box designs like the one OP is suggesting was having trouble with the engine overheating. Most of these box fans use the air to cool off the internals. If it doesn’t get that for many hours, it can start overheating. Just check after running whatever solution you come up with and make sure the engine isn’t getting hot.
I tried that single-filter design in the past, and it seemed to do a poor job of filtering the air, and it stressed out the fan motor a lot.
Im not saying your wrong but that design and that spefic fan is over a decade old now.
It might just be the brand/specific motor that people get on the market.
I haven’t heard anything about box fans overheating with the boxes on the back and I’ve been following these builds on Reddit for 2 years before I built one. The general consensus is there’s MORE air flow with the box.
Get a heat gun. You can see it happening in real time. Or not if its not.
Its good not to trust me, as I didnt put any real data on what we did here. But it should be self evident if you make the build,. run the system for a while, then check the temperature. You dont want to strap a ton of flammable material near an engine that could get hot. Also if we were to do real science, I bet its because certain fans are older/have less oil/etc…which causes a buildup of heat.