Kid1 put together this computer fan based #CRBox
Works great - fairly quiet.
Parts cost about USD$130 (with an extra set of filters for later) with as much as possible from local hardware store
Air Support Project is proud to announce that we have received a grant from the Balvi Foundation, an organization initiated by Vitalik Buterin that focuses on funding high-impact, open-source COVID projects. Learn more about our Open-Source Prototype in our newest Blog, Breathing Innovation: https://airsupportproject.com/breathing-innovation-air-support-projects-open-source-prototype/
Time to build: about 45 mins (not including soldering the power supply)
Materials:
(4) $5 Arctic P12 fans
(2) $10 10x20x1 1200D filtrete MERV-11 filters
(2) $7 20x20x1 1500 MERV-12 filtrete filters (pack of 12 off ebay)
duct tape
zip ties
cardboard
12V power supply (free because I soldered a random old adapter, but normally $10 plus $3 or so for a splitter. Or get the fans with built-in splitters)
Total: approx $55, next one will cost about $70.
Roughly 225cfm and extremely quiet. #CRBox
Here's the 4 PC fan #CRBox next to a traditional 20" box fan CR Box. I'm betting I could fit 8 PC fans with those same filters. Cutting the shroud for the box fan is the biggest hassle of a traditional CR box, I really appreciated not having to worry about that for the PC fan version.
So some back-of-the-envelope math... A normal #CRBox using 4 20x20x1 filters has 1600 sq inches of surface area*. Additional surface area means less air resistance, and therefore the fans are more capable of hitting their spec'd air flow. Since I normally put my CR Boxes against the wall, I only use 3 filters with a surface area of 1200 sq in.
Pleated, and definitely not uniform between furnace filter manufacturers. Hence back-of-the-envelope.
Old box fan #CRBox and the new pc fan one that's replacing it. Based on https://www.texairfilters.com/an-easy-to-build-corsi-rosenthal-box-using-modular-pc-fan-systems/ , although I used 1" filters instead of 2" filters for half of them (which was a mistake. Don't do that. The 1" filters are 1/4" longer than the 2" filters, making everything just slightly more annoying to build. Should've just waited for more 2" filters to ship.)
Those PC fans are pricy, but still cheaper than a commerical HEPA filter and somehow more effective. My Coway AP-1512HH performs worse.
The first time I was going to build a Corsi–Rosenthal Box I accidently built a Creutzfeldt–Jakob Box, and we didn't know what the hell we were even doing for weeks.
The second time it turned out I had the plans for a Dunning-Kruger Box but I persevered anyway, and it turned out brilliantly. Everyone said I was an idiot but they just didn't understand how amazing I am.
I have one #CRBox that is 7 months old (3 filter design), and because of its location is brown and covered with dust and cat hair. I'm thinking about trashing the filters on that one. Another two 3-filter CRBoxes are the same age, and still look pretty clean.
I built my first #corsiRosenthalBox today with supplies I picked up at Canadian Tire. You can get the same stuff cheaper at Home Despot.
I bought:
1x Lasko 20" box fan - $49.99
4x 3M MPR1900 MERV 13 ultra allergen & virus 20"x20"x2" - $33.00
(The cheaper ones were on sale for $17.99. Get them. They're just as good but we're out.)
I had:
1x roll of white gorilla duct tape. Use any kind, just make sure it will make a good airtight seal.
Recycle the fan's box into the bottom of the #crbox, cut off the flaps to cover the gaps at the corners and you're done.
I'm seriously impressed with this thing. Even on the low setting it pulls a LOT of air. On high, it would do well to filter an office.
The Virtual Clean Indoor Air Expo is Tuesday 10-24, from 2pm- 10pm EDT, the Zoom Events Registrations hit their max, so @whn is live-streaming it at https://www.youtube.com/live/mCpjnh9cz7U?si=xbz5Ac8ejUsZ7RLc Watch to learn more about why you should tune in at
I'm getting really excited about the all virtual Clean Air Expo, it is going to quick talks from a variety of speakers, QA sessions with panel discussions, expo booths, all sorts of topics, hosted by @whn , THIS TUESDAY, Oct. 24th,- 2pm-9pm EDT, if you havent checked it out or registered, you should, so you can join us on Zoom for all or any parts, learn more/register at https://www.cleanairexpo.global/
So is anyone aware of premade CR boxes, or kits, available to purchase?
I need to come up with a couple in the next two of weeks. I already have one box fan, and a hardware that doubtless can provide the materials. I know there are quantities of plans out there on the web.
But if I could somehow just cause a couple of these to show up at my house, it would make things soooo much easier..
Six month #CRBox filter change and fan maintenance. Easy and effective #AirQuality improvement and one layer of defense for #SARSCoV2 & #FireSmoke (dust, pollen, dander....)
(This time assembled with pleats in the vertical orientation for better stability.)
Outside, the #temtop monitor says the #AQI is 140.
We went over to my in-laws, where they had the windows closed and had some window AC units running - the AQI inside was around 120 and stable.
I brought a 3-filter #CRBox over and plugged it in (on low). Within 10 mins, AQI was in the 70s. It slowed down at that point, but after running for an hour AQI is currently 43 and still slowly dropping. #smoke
The sweet spot I've found for a #CRBox, between cost, noise, robustness, and flexibility, is 3 filters.
4 filters only allows you to face it one way. It also wastes 1 filter face if you need to put it next to a wall.
1 filter is (much) noisier.
2 filters (in a cube) is okay, but sometimes restricts where you can place the box. You only have 2 usable sides; so maybe a corner or hallway doesn't work because the wall blocks a filter face & now you only have 1 filter with decent air flow.
@jaybaltz My data shows that a #CRBox with MERV 13 filters is remarkably effective. I turned it on at the peak of this graph.
And they are also more comfortable to wear on your head (mostly cardboard) although my data shows that they even clean the air in adjacent rooms. @johnefrancis