I recently stayed in an apartment that didnt have central air so I created a corsi-rosenthal box since the smoke from the Canadian wildfires were so bad.
After 30 days of continuous use, with very minimal periods of it being turned off, this is what the filters look like!
It’s disgusting yet also so satisfying to see the filters get darker from debris, dust, and dirt.
Edit: typos
I’m just amazed it apparently took two people to think of taping 4 air filters together with a fan on top.
They may not have been the ones who first thought of it, but the first people to publish research that shows that taping 4 air filters together with a fan works decently compared to other, non-DIY filters (where “worked decently” means does a good enough job that it’s worth doing if you want a filter but can’t/won’t buy or build a more complex filtering system, even if it isn’t as good as “proper” filtering systems)
(Tangent: I’m reminded of the “Cox-Zucker machine”, a random maths thing that Cox and Zucker made together because when Cox and Zucker met at university, they realised that their names, when combined in the traditional, alphabetical order, sounded “delightfully obscene”. )
I totally did not realize how much real science was behind these things. I mean this design is so simple and obvious, it seems like something I would throw together because it just looks like it “should” work. And according to the research I just read they are very efficient and effective. Super cool!!!
I think the science comes in showing that it does actually work. Like, this is so simple of an idea that I would be skeptical of if it would work if I had had the idea by myself. I’m glad that I live in a world where, if I had thought of this and wondered “is this a good idea, or am I just being dumb for thinking something so simple could work?”, I am able to go online and find information and guides on this and other diy filters
“Corsi-Rosenthal Box” sounds like it’s some theoretical physics thought experiment, but no it’s some filters and a box fan.
Be tempted to build one of those for my shop.
I thought it was for filtering weed smoke, designed by the famous grower and strain creator Ed Rosenthal.
Think it was a covid thing.
No word on ed being the rosenthal in question.
These have been around for a long time as DIY filters for folks, I remember seeing one of these on Reddit before comments were a thing.
Once upon a time Reddit drove you to interact with other websites instead of shitposting your best hot take about the title of the post someone else didn’t even visit.
Comments truly ruined Reddit
Long time ago I made my own activated carbon filter from plans I found online out of chicken wire, some duct parts, of course activated carbon, and pantyhose. got some funny looks when buying that last one, but it worked like a freaking charm.
custom filters are common in the aquarium hobby, lots of fun pipe fittings to play with
Someone posted a link to Wikipedia in the comments, came across their names:
Richard Corsi, an environmental engineer and the incoming Dean of Engineering at the University of California, Davis
Jim Rosenthal, the CEO of filter manufacturer Tex-Air Filters
Oh, that’s disappointing.
could be his brother
Not the weed guy though.
Oh. A CEO of a filter company. I sort of wondered why I couldn’t just tape a single filter to a fan, why it required four of them. Maybe it has something to do with air flow limitations, or maybe it has something to do with the guy making a profit on every filter sold lol
That a good idea ! Didn’t think about it.
well…
A 2022 study found the clean air delivery rate on the five-filter design was between 600 and 850 cubic feet (17–24 m3) per minute (depending on fan speed), costing roughly a tenth of commercial air filters.
hope you can keep up!
Yeah may be a little overkill
I’m going to start talking in vague terms about my own designs for a “Corsi-Rosenthal Box” when I want to sound smart.
It’ll be great if anyone bothers to look it up.
I mean, it sounds like an Einstein-Rosen bridge.
“My Corsi-Rosenthal Box is designed to efficiently accelerate particles inwards. The particles are then ‘captured’ using a special filtering technique, and separated from the air molecules which are allowed through.”
It’s removing particulates though.
So you could call it and “anti-particulate vertical fluid acceleration device” maybe.
TIL about the Corsi-Rosenthal Box
It is by far the best air purifier you can get for the money.
I got MERV 13 filters to help with my kids allergies. Inside the house, perfectly fine, but once outside it’s sneezing and runny noses. It’s amazing.
Do you know how much power it uses?
the PC fan version uses 10W max
Techingredients just did a video on ceiling fan designs and realized that DC motors are vastly more efficient.
They also figured the cost savings to pay for the motor change, and it didn’t take long to pay off.
Hi, electrical systems engineer with an offgrid solar system powering fans I tested with meters signing in.
The typical fans you can buy in consumer stores are about 100W on average a little less on low aroubd 80w a little more on high like 110-120w.
They make more energy efficient fans, particularly brushless motor DC powered fans meant for marine boating power systems are incredibly energy efficient and quiet but they’re also incredibly expensive.
Also keep in mind consumer fans kind of suck compared to a true industrial fan which can take a lot more power for serious wind speed output which the Wikipedia for this device says improves efficiency of purification. You can get power tool industrial fans that run off dewalt tool type batteries that are low DC voltage but high amperage, they’ll be more powerful than typical consumer fans too but run out of juice battery wise within hours.
I personally like the 10-15watt DC fans with pass through USBC charging for personal cooling but thats not what were talking about.
I looked up a 20 inch box fan on Amazon and it was rated for 67 watts. I ran it almost 24 hrs a day(kids loved to mess with it) and didn’t notice it on my bill.
67 watts is 1.608 kilowatt hours per day. In California (one of the more expensive states for electricity), electricity costs $0.31/kwh. That would come to just under $0.50/day or $15/month.
Watts per hour isn’t a thing. Watts is already a measurement of rate. 67 watts, running for 24 hours, is 1.608 kilowatt-hours.
The rest of your math checks out, assuming no hidden “distribution” or “transmission” fees (like I have).
Thanks for the clarification. Fixed.
Been aware of the general idea for a long time, but had no idea that strapping HEPA filters to a fan has a fancy name.
You have to cut some cardboard and use tape too. After when your solution beat every commercial solution you are allowed to name it, just to be able to shame corpo easily.
Could use those circular filters stacked on each other and a fan at the top. Name it my column.
Didgeridoo air filter is also tempting me now.
Dongderidong air filter ?
I’ve put an air filter in the bedroom next to the bed. Makes nice white noise too. I also have one next to the cat’s litter box. I’m thinking of putting one in the bathroom because the toilet paper makes an insane amount of lint that builds up everywhere.
I built one back when I lived in California during fire season, and then again during the pandemic. They do such a nice job making the air less gross.
I think that’s about what mine looked like after 3 or 4 weeks too…
Can you talk about how you made this
It’s literally what you see in the picture. Just household furnace filters taped into a box with a fan. You can pick your level of filtration with the type of filters you buy.
Does the fan suck or blow, and why? I seem to recall that the motor will burn out if you face it the wrong way.
It is setup to pull in air through the filters into the box and push it up through the top.
Looks like it’s sucking air through the filters.
I would imagine it blows upwards, so it sucks in air through the filters and blows clean air up.
In that pic it’s blowing up, sucking intake through the filters and blowing filtered air into the room.
UC Davis has a video on how to build one.
make sure you get merv 13 or higher for smoke. the filters get gross fast even with 8 but you can tell the difference when you breathe.
I have 2 to 4 of these going at all times and the 8s are full time and 13+ are periodic unless fire season.
correct me if I’m wrong but anything higher than MERV 13 has diminishing returns because of increased resistance. instead of going for increased MERV I recommend getting thicker MERV 13 because of their bigger surface area.
CR boxes rely on raw total air volume and increased ACH vs HEPA which relies on filtering as much air as possible on the first pass.
If you go for the 2” thick filters they breathe better and have more surface area.
We did one with just one filter on the intake side. Kinda like this one better. But it takes up more room than mine. I’ll have to do some experimenting.
Corsi-rosenthal box is stupid efficient.
Now imagine that, but in your lungs. Yikes.
lungs are self cleaning, dirt just dosent stay in there it gets pushed out again by tiny moving hairs
… mostly into your stomach.
I have great news for you about what happens to the contents of the stomach!
dont worry they mix with the microplastics down there
I mean, yes.
But like, they have to, without the filter.
Some dirt gets pushed out and sum just stays
Wow that’s really quick for saturating those filters! Wildfire season is the worst.
I really need to make one of these.
My loft is so freaking hot I’m sweltering. Could something like this keep my loft cooler, the window unit is struggling to cool it off until late at night
No. This actually will heat up your apartment by a measurable amount. This is purely an air quality type thing.
*measurable if you have some damn good instruments.
It will put off about as much heat as a single incandescent light bulb
Fair, and I would say < an incandescent bulb. Cause I’m damn near 40 and remember getting a good MiB experience touching one.
OP likes it dirty!
This is a great reminder to clean my computer fans.
