CleanAirKits - Corsi-Rosenthal Box

An extremely effective option is a Corsi Rosenthal box, they're diy and dirt cheap, but kind of ugly. Just Google Corsi Rosenthal box and there are directions everywhere, or you can buy an assembly kit on Etsy for pretty cheap

A CR box made with computer fans (like [this kit](https://www.cleanairkits.com/)). The nice thing is that the filters are generic MERV 13 filters, which are fairly widely available.

The best is a Corsi Rosenthal box. You can make your own but people have started to make fancy enclosures and you'd just need to change out the HVAC filters as needed. They're the best performing and quieter than commercial units with their proprietary filters. https://www.cleanairkits.com/ is an example.

I'm here to pile on to the "Corsi Cube" brigade - they are the cheapest and work the best!

I am currently running the house special of "I bought whatever was on sale at the time." So I have a mix of Levoit, Winix, Blueair, and a couple of decades old Honeywells to round it out. My AC system also has a "circulate" option and has a built-in HEPA filter and UV light. I monitor it all with a Airthings 2960 (one upstairs, one downstairs). Currently, I am trying to consolidate to a single brand (settled on Levoit - 300 and 600 sizes) just to make filter replacement simpler. Trying to get to a 6mo filter replacement schedule (currently closer to 4mo here in Texas, thanks to all the allergens). From my testing, here's the short version - as long as it moves air and has some sort of filtration, it'll probably help the air quality in your home. Everything else - air quality monitoring, app access, noise level - it's all bonus features that don't really affect the overall performance of the device. According to my Airthings AQ monitor, they do make a difference. I see VoCs and PM1 and PM2.5 go down when you ramp up the filter fan speeds. For recommendations - Level 1 - regularly change the air filter that your home uses - go cheap and replace more frequently rather than going expensive and hoping it lasts longer. Also, vacuum and dust regularly. Level 2 - bang-for-the-buck is the Corsi–Rosenthal box - and it will always be what I recommend to people who are trying to figure out if air filters will make a difference for them. Level 3 - buy the system that moves the most amount of air and has replacement filters that don't cost an arm and a leg. Levoit, Winix, Blueair, are all honestly decent systems - and if you open them up to replace their filters, you find out that they're really just doing the same thing the Corsi-Rosenthal is. They're just intake fans sitting on top of a filter. As price goes up, you're really just paying for things like automation (fan automatically ramping up when it senses high particles), noise reduction, filter change nagging, etc. My suggestion is to buy whatever goes on sale next time and stick with the brand/size for ease of maintenance. Minimum size I'd recommend is 1000sqft even if your home/room is smaller than that. The max room size is calculated by their highest fan speed - chances are, you probably won't be running it that high all the time. It is better to get multiple smaller units that are local to the area you're using versus a single large unit for a big space. These do not move air vigorously (less than your standard fan) - so even if they say they'll do "3000sqft" - they are assuming you're in a single rectangular room with only four walls. If your home is 2000sqft with lots of rooms and hallways, a single unit will not work. However, the number one thing about any air filter is that they are a continuous cost and will only work as long as you are regularly replacing their filter media. At least with air filters you will be able to see exactly what they're doing when you replace them - mine are usually pretty grey-looking by the time I take them out. Oh, I wouldn't bother with all of the fancy filters (like pet, charcoal, or whatever) unless you have a very specific need for them. Those are are mostly gimmicky. Air quality monitors (like the Airthings) are also not needed - and in fact, many of the higher end filters have particulate sensors in them. It's mostly informational for people like me who just really wanted to know if all of these filters actually did anything. Plus, AQ monitors don't tell you *what* the stuff in the air is, they just tell you it's high. I found out that vaporizing humidifiers make PM sensors show deep red spikes because they're literally throwing tiny bits of water into the air (but it's not specifically a negative thing - especially when you're trying to raise humidity). For the "do they work?" question, my answer is "Eh... sorta." They definitely help with things like odors (such as from cooking or pets). I have not noticed a huge decrease in dust build up (but my house is not sealed in any shape). I definitely notice that my allergies get worse when I go outside versus hiding in my house, but it's not like they're completely eliminated when I'm home. So for me at least, they help, but they're not some sort of miracle cure that'll magically fix everything.

I have multiple air filter systems from Clean Air Kits and I love them. They use standard AC/Furnace filters, are super quiet, and do an incredible job removing dust and other contaminants. https://www.cleanairkits.com/ Since we started using them, our house has been noticeably less dusty, and I can see that the one in our kitchen removes cooking smoke about as fast as it comes off the stove.

Yep made a corsi rosenthal and it’s the only air purifier that I’ve actually noticed a difference with my allergies

[Northbox](https://aidankepo.wixsite.com/northboxsystems) PC-fan Corsi-Rosenthal boxes. Quiet, high CADR.

Why would I recommend a quiet, high CADR PC-fan CR box? Because loud purifiers don't get used, or only get used at a low speed that doesn't provide the full rated CADR. OP was looking for, among other things, airborne virus protection. You want 24/7 maximum dust CADR to prevent indoor disease transmission. Dialing the purifier down because it's "too noisy" defeats the purpose. Indoor smoke will typically only permeate at whatever low ACH the building's envelope leakage permits, so this application doesn't necessarily need the 24/7 maximum CADR that airborne virus transmission does. No doubt a higher CADR DIY solution can be built, but it's not obvious how to easily make it quieter for the same CADR. "HEPA" seems like a red herring for air-purifier applications. CADR is king, not single-pass filtration efficiency. Similarly, pre-filtering doesn't seem as relevant if you're using relatively inexpensive MERV-13 furnace filters rather than expensive/proprietary HEPA consumables. In actual use, CR boxes easily deliver 6 months of filter life before significant dust/debris accumulation. And in a smoke application, you'd probably want to replace the filter after each major smoke event due to the smoke's effect on filter efficiency, regardless of dust accumulation. While higher CADRs are certainly available for situations where occupants are noise-tolerant, there's value to a ready-made solution that won't prompt cries of "turn that thing down already!"

Google “Corsi-rosenthal box”. There is nothing more effective than this without spending thousands

Corsi box is where it's at. Ours is with 2'x4' filters. Sits in the foyer with high 2nd story ceilings and open to formal living, dining, and kitchen (easily 2k+ sqft), been on 24-7 for 4 years.

We built a Corsi-Rosenthal box using materials from the still-open Home Depot. All you need is four 20x20x1 MER 13 filters (coincidentally 50% off when you buy four), and a 20" box fan. It's the single best air purifier you can get, and it's one of the cheapest and most accessible. Ran us about $40 at Home Depot last night, and it cleared up all the smoke in our apartment in no time. I recommend also sealing your doors and windows with duct tape, which you'll need anyways to build the filter. Instructions for assembly: https://corsirosenthalfoundation.org/instructions/

[Corsi-Rosenthal Box Instructions](https://engineering.ucdavis.edu/news/science-action-how-build-corsi-rosenthal-box) Build a Corsi-Rosenthal Box. 4 MERV 13 filters, a 20" Box fan, and about 1/4 roll of Duct Tape. They also sell pre-made frames if you look around. ~$80USD.

They absolutely do work. If you don't mind the look, a Corsi-Rosenthal Box takes 15 minutes and about $70 to build and is much more effective than any standard HEPA purifier. Filters out less small particles than HEPA, but because the sheer volume of air passing through it ends up being more effective anyway.

How often do you cycle it on and off? I have a diy corsi-rosenthal box that I just run 24/7 on low

nobody has thrown it out there so I'll mention a corsi-rosenthal box. I made one last year and while I don't have a regular air purifier to compare against, I think it's been doing a pretty good job. The filters were disgusting after 6 months, anyway, which I doubt would be the case if it wasn't pulling in quite a bit of junk from the air. might be worth a shot, especially with how bad the air quality is rn

Yeah, as long as you’re cool with how ugly it might look, and also cool with rebuilding it at least twice a year, the price performance ratio basically only gets beaten by commercial options. It’s also certainly not buy it for life, but I think it’s always worth bringing up regardless just because of how easy and cheap and good it is, it’s way better than buying a fancy one and risking it taking a shit in two years.

My setup is similar! I use my Ikea Vindstyrka and a Sonoff wall outlet to control my Corsi-Rosenthal Box (https://engineering.ucdavis.edu/news/science-action-how-build-corsi-rosenthal-box). The fan is set to low because it works very well with minimum noise. I initially built the filter box to manage dust during my snail-paced DIY remodel, which also includes a major project to fully monitor and automate my home. I got the Vindstyrka to monitor the interior air when I got a weather station to monitor the exterior. Added the automation soon after as one of my first HA automations. I may eventually upgrade the sensor and purifier, though I'm beyond impressed with how well this extremely basic system works for a total investment of under US$150.

i recommend [building a corsi-rosenthal box](https://www.reddit.com/media?url=https%3A%2F%2Fpreview.redd.it%2Fhow-to-build-a-corsi-rosenthal-box-v0-7lsewtlsza3a1.jpg%3Fwidth%3D1080%26crop%3Dsmart%26auto%3Dwebp%26s%3D750ef76a074e61f50008f0acb28f82f9e46da731), if only as a temporary solution. they work better than many commercial air purifiers. you can also make one that’s a triangle with only two air filters instead of four. it’ll work slightly less well but it’ll still work.

https://en.m.wikipedia.org/wiki/Corsi%E2%80%93Rosenthal_Box That will work way better. All you need is one fan and four filters. Way less static pressure for the fan. Actually one of the best, filters period

I made my own and set them around the house. https://cleanaircrew.org/box-fan-filters/

This, sometimes calles Corsi-Rosenthal box. https://en.wikipedia.org/wiki/Corsi%E2%80%93Rosenthal_Box

CR box, probably.

For under $100, you can build a Corsi Rosenthal box or other DIY air purifier that is just as effective as some commercial products that cost at least $1000.

I've got a corsi Rosenthal box, a levoit, a Honeywell, and one other than I can't remember the brand of right now. The CR box has a high CADR but is noisy. Works great for clearing the air or when I have guests over. The levoit is quietest and I use that in my bedroom. Makes nice background noise. The Honeywell is fine. Picked it up 2nd hand from a thrift store for $10. I use to just help keep dust and pet dander out of the air.

This is what I use. I have a couple set up, one on the main floor and one near my pet (guinea pig) cages. Does a great job. Yeah it's ugly, but the only cost is the fan and the filters themselves, and it really works.

Great post! I would also add cleanairkits.com for the quiet, high CADR air filters.   I would also potentially add a caution around the far-uv (I own the Nukit and am happy with them) that I believe you should avoid prolonged use in a room that has little ventilation.  I'm intrigued by the smaller AirFanta laminar fan :)

Very much so. They have cleared out good vapors and wildfire smoke reliably for us, and might have reduced the amount of infections resulting from play dates. I’d add a vote to build your own Corsi Rosenthal box from large MERV filters, a fan and duct tape.

Good call on the corsi-rosenthal box. I have a Honeywell. Though it can run insanely quiet compared to my CR box. I ended up hacking the PCB of the Honeywell to add automation via an ESP32. The CR box runs in the basement so it's just on a smart outlet. Also nice building it with aluminum. I did mine out of furring strips and cabinet screws. Lol.

I love my CR boxes but I get that they're not for everyone. I have a Bissell Air 400 for my bedroom specifically because it's oversized for the room (better efficiency) since I have bad tree pollen allergies. I've been very happy with it.

My wife built two of these for our house. She despises dust. They work pretty well.

One is in the front door foyer to blow up the stairs. The other is in the living room. We have a dog that sheds a lot and that's where he spends much of his day.

They work. Most are over priced though and the filters cost an arm and a leg and are where the profit is at. Most people could get away with a Corsi-Rosenthal Box, connected to a smart plug and turn it on when they cook for a drastic improvement in indoor air quality for cheap.

If you're looking to collect dust - you should make a Corsi-Rosenthal box. A HEPA isn't going to process enough air for really getting rid of dust. If you don't want to make one yourself, or want a nicer aesthetic, check out Clean Air Kit. Here's an [informative video](https://youtu.be/gaQTYrisieA?si=mjj8lAmHywe_exSu) on this topic.

Second the corsi rosenthal box. You'd need to pay 4x the price at least for comparable filtering

"Corsi-Rosenthal Box" is the way to go if you don't care about aesthetic. It's really effective for larger sq footage rooms

budget budget, build a corsi-rosenthal  otherwise, get a coway airmega. it's a little pricier than some but it has a carbon filter which is great for smells. prefilter catches a lot and saves wear and tear on the hepa panel

You can literally press a cheap furnace filter onto a running box fan to make one. It will suction itself on. Tape on the top of it if you want to move it around, check how dirty it is by hand or by flow. Technically 1 filter to 1 box fan reduces the flow, but it works. 4 filter intakes for 1 box fan is the practical/high efficiency setup people like which are called: Corsi-Rosenthal Box setups

Look up a Corsi-Rosenthal box. The modern world has a ton of cheap, reasonably high quality air filters built for furnaces in every hardware store. The cost of high end air filtration vs what a CR Box can do is pretty silly unless you're allergic or have money to burn. There are even designs and builds specifically to be more permanent than the intial construction method so you can spend 50-75 bucks on parts, then just swap filters and have something that works for like a decade.

Don't get it. Make a Corsi-Rosenthal Box. It is a higher value than a huge majority of filters you can buy, and a 4yo can make it in a minute. You can use whatever filters you want on it, and it moves more air too.