The filters in my Corsi-Rosenthal Box look after 30 days of continuous use...
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
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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.
https://www.techingredients.com/videos
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 ?
from huppakke:
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
take what you will from this, but it's definitely not a stick-it-to-the-corp kinda thing
Yeah I was trying a joke. It still beat commercial alternatives which I fell is a Second good reason to give it a name.
"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'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.
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.
Someone posted a link to Wikipedia in the comments, came across their names:
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
Pretty sure its about creating negative suction below the fan. Instead of just pulling air from the intake side of the fan, its pulling it from all 4 directions. Theoretically the air flow going through the filter would be at least 4x but probably more in practice.
Well the rate of airflow through the fan is at its maximum when there are no filters attached to it. Each filter likely slows down airflow if hooked up in a "series" pattern, but you're right that having these four in "parallel" will increase flow compared to one strapped directly to it. I'm sure there's a problem with reducing the airflow too much, because the fans motor would start to burn, and I'd guess that hoisting the fan up in the air rather than standing upright on the ground would improve airflow.
That being said, I'd need to do it myself and see what strapping a single filter to a fan does. I have hunch it wouldn't burn out the motor, and I imagine it'd still be effective. If the rate of airflow isn't severely reduced with a single filter, that'd just mean the same amount of air is being forced through a filter in either case (1 vs 4 filters).
Of course the single filter would wear out four times as fast so it probably won't make a difference in how many you buy in the long run. I'm just sort of rambling at this point but it's a neat concept to think about.
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
That a good idea ! Didn't think about it.
well..
hope you can keep up!
Yeah may be a little overkill
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!
It also gets pushed out! (Normally)
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
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
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". )
Curious why it's not 5 filters with some little toilet paper tubes or something for legs. Was it found that the fifth filter is diminishing returns?
Sounds like an argument that would take at least two meetings and a dozen emails if this were done by a company lol.
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.
this is true. I pick up filters from shut down businesses and warehouses sometimes when people dont know what they cost and post them to fbm or craigslist and if they are higher than 13 I also put a filter for the bottom panel since I usually hang them blowing down with cords taped at the corners. even then they start to suck inward.
Hey, I have that same rug
It really ties the room together
Yeah, well, you know, that's just, like, your opinion, man.
I have the same box fan
i have the same duct tape
Will all of you get out of my house?!?!
Nope, the air is good here. Have any beer?
I saw a couple left in the fridge. Will you grab more chips while you're up, please?
Link? Used to have one like that but now I can't find another one
You're not a true lemmy unless you own The Rug
I got it from my parents after they didn't want it anymore, but I think they got it from IKEA
Those start out white?? I think it's time to replace mine.
Ya, they were brand new filters from the store. I bought them along with the box fan and duct tape.
This apartment doesnt have a HVAC system (just wall mounted AC unit) so it's doing all the air filtration.
This is why I buy my HVAC filters in bulk 4 or 8 at a time and replace them every 3-4 months (less if there is smoke). The difference it makes in keeping the house clean is very noticable. I get very little dust accumulation except in my teens rooms because they leave their doors closed.
I buy these and swap as needed
https://www.homedepot.com/p/HDX-20-in-x-20-in-x-1-in-Standard-Pleated-Furnace-Air-Filter-FPR-5-MERV-8-12-Pack-HDXCP5-012020/332831164
Christ i wish we could get these filters in au at non-arserapey prices
I read that as "our-SER-uh-pee" at first. I now have a new adjective.
Say it in a pirate accent
Is that a portmanteau made from "arse" and "therapy"? Because I might be interested.
have you heard of the Ikea Starkvind filters? they're a bit smaller but you can tape together as many as you want
Theres a way i bet. You just need the filter dimensions to match the fan on one axis.
You can make them yourself using felt, wire and glue. Might not be exactly as effective but better than nothing.
Can you order from Alibaba?
Post a new one for comparison.
You can eference the outer edges for a satisfying before/after.
Filtering can be a rabbit hole.
Yes it can!
I was a little miffed when i went to buy the goods for this box because i couldn't get MERV 14 filters and had to settle for MERV 13.
I plan to make a frame so i can just slide filters in each side with the fan mounted on top. I'll have to figure out a means to create a nice seal between the frame and filters so the air passes through instead of around.
Flexible weather stripping for doors is good for this.
Ohhhhh that's a great idea! Thanks for the suggestion!
Now it matches the rug & walls, though
Funny enough I cleaned that rug after first moving in (apartment was pre-furnished) and it looked clean for a whole day.
I feel ya. My house was miles away from the evacuation zone of the PacNW fires a little ways back, and the filters didn't last the month. We wore masks with filters rated for smoke whenever we had to go outside, and sealed every external seam, hoping the firefighters could get it under control in time. Thankfully, they're the public servants that actually know what that phrase means, and to the enth degree. I trust every one of them right alongside our Nat'l Park service members (rangers, et al), sight unseen.
When this nation's collapse comes to your town, remember this simple rule, fellow US peeps:
Firefighters & National Park Service? Heroes of the people, through & through.
Cops, etc.? Shoot on sight (if that's your chosen theme for the apoc, ofc.) 😅
I really need to make one of these.
Good job, Captain Lovell. That’s some Apollo 13-level engineering right there.
Just doing my part ground control 🫡
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.
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.
It is setup to pull in air through the filters into the box and push it up through the top.
UC Davis has a video on how to build one.
Ok. I've been looking into this a lil and there are better options than a cr box.
Housefresh has been looking into this and they recommend the nukit tempest or luggable XL or another one - think it was a Canadian brand - as the cheapest total costs over time and lowest sound and most efficient purification. All of those use regular HVAC filters which cuts down on operating cost and are quite big which cuts down electricity and sound.
So recommend getting one of those for long term use, if you have the space for it.
There's also an open source tempest that you can use a CNC for and customize to your liking with a script. https://github.com/opennukit/Nukit-Open-Air-Purifier/tree/main/Nukit%20Open%20Air%20Purifier-W(all)%20v1.0
I have an unfinished project to make a nukit with a power knob.
I got a cardboard proof of concept working but need to make my mark 1 out of plywood or something else.
Duct tape an electrical knob device to the front and call it a day?
Can you put a bag of ice in this for simple ac?
You would have to go out and buy ice, if you use your own fridge to make the ice you will have a net negative energy also just buy a cheap AC, it would save so, so much energy.
Oh, leaving the house? Yeah sorry i don't put pants on anymore. Good call.
Just get the ice delivered from the local grocery store.
Oh, that's an interesting idea, not too much different from a swamp cooler actually so ya I think it would work.
My question is, where would be the optimal spot for the ice/icepacks:
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...
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.
These are great, but if you’re looking for something slightly less bulky, there’s a dude selling kits online using pc fans. I’ve got two and they’re pretty much a CR box in its final form. Kits come with laser cut panels, fans, grates, etc. only need to supply two filters. Way quieter than a box fan. They’re a bit pricey but worth since they can pretty much be placed anywhere.
google clean air kits.
For that money, you can buy actual air filtration units. The box fan may be noisy, but something that big is going to have massive surface area and provide a lot of filtration.
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.
Wow that’s really quick for saturating those filters! Wildfire season is the worst.
I'm viewing this post with the Thunder app and I only see one photo: a box with a fan on top. I see no filter. Is there supposed to be a second photo?
The box is the filter
What you see are 4 hepa filter plates taped together into a box, with a fan on top. The fan blows air upwards, thus creating a low pressure environment inside the box, which sucks the air through the filters - which are originally starch white.
Yep and if you want to get really fancy, ya can put the box on stilts and put a 5th filter on the bottom!
Replacing those has got to be a pain with the amount of duct tape you used. And why is there tape on the bottom?
I used the box from the box fan to create a bottom to make it a bit more sturdy for moving around and ensure more air flows through the filters instead of slipping in under the filters.
It also helped making the CR Box easier. I used it as a mount point for each filter.
I duct taped the filter to the bottom piece creating a sort of hinge that let the filter lay flat outward.
I then would prop up two filters creating a corner and tape them on the inside and outside.
Then I'd do the same with the two remaining filters. Then finally tape the final two corners.
The next step i do is optional, but it made taping the fan on top easier. I created a fan shield, which is like the bottom but a big hole in the middle. Tape that on top.
Finally, place the fan on top tape it and try to seal any gaps.
You can just cut the tape at the top along the fan, than peel the left over tape off the fan and start again. The tape on the bottom is for either a 5th filter or just a peice of cardboard across the bottom for stability.
You just cut the tape off. They last a pretty long time. I've got one going for two years intermittently here. If it looks too rough, you can take it out side and use a vacuum or air compressor to remove a lot of the surface dust.
Tape on the bottom is for the bottom panel. Usually it's just a cardboard sheet.
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!
I dont mean airflow as in rate of air moving through the fan, i mean it as in volume of air being filtered.