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.
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.
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”. )
Hey, I have that same rug
It really ties the room together
Yeah, well, you know, that’s just, like, your opinion, man.
Do you have the link for it? So we can all have one.
You’re not a true lemmy unless you own The Rug
Lemmy’s ‘Upvote Soup’?
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?
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.
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
I mean, yes.
But like, they have to, without the filter.
Some dirt gets pushed out and sum just stays
… mostly into your stomach.
dont worry they mix with the microplastics down there
I have great news for you about what happens to the contents of the stomach!
It also gets pushed out! (Normally)
TIL about the Corsi-Rosenthal Box
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.
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.
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?
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 per hour is 1.608 kilowatts a 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.
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.
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 Open Air Purifier-W(all) v1.0
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:
- Inside, at the bottom
- Inside, suspended in the middle
- Inside, at the top near the fan
I really need to make one of these.
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.
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?
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!
The box is the filter
Replacing those has got to be a pain with the amount of duct tape you used. And why is there tape on the bottom?
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 to 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.
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.
Can you talk about how you made this
UC Davis has a video on how to build one.
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.
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.
I would imagine it blows upwards, so it sucks in air through the filters and blows clean air up.
Looks like it’s sucking air through the filters.
Post a new one for comparison.
You can eference the outer edges for a satisfying before/after.
Good job, Captain Lovell. That’s some Apollo 13-level engineering right there.
Just doing my part ground control 🫡
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
