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

I still love my Corsi Rosenthal air purifier.  Its on an Alexa plug and turns on at night in my living room. 

If i wanted to upgrade from my CorsiRosenthal, this is where I'd start. https://www.cleanairkits.com/

I've bought a couple of Luggable air filters from [Clean Air Kits](https://www.cleanairkits.com/) that seem to work really well. They're tall but skinny. They're built with computer cooling fans, so they move huge amounts of air very quietly. And they use the same Filtrete MPR1900 filters that you would use in a furnace/central air system.

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 only viable option for affordability short term and long term.

r/crboxes Cheapest and best option available both up front and over time https://www.cleanairkits.com/ just an example of a pre-made kit, I'd recommend making something with a 4-5" thick filtration medium for longevity over buying a 1" filter kit. Those 4" filters last a year for $90 The total cost of a project like this should run you about $200-300 depending on what fans and materials you use

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.

best air filters I've ever found: [https://www.cleanairkits.com/](https://www.cleanairkits.com/) inexpensive, use filters you can pick up at your local hardware store, quiet, and can be controlled with a smart plug if you really want to turn them off. pair those with some Awair sensors and you have a very good set of metrics for the home. IMHO an air filter itself doesn't need to be "smart," it needs to be inexpensive, easy to use, easy to clean/change out, and have no circuit boards that can break down, leaving you with bad air. If you want to go the other direction, you could go with something like the [Trane whole home air cleaner](https://www.trane.com/residential/en/products/indoor-air-quality/air-purification/cleaneffects/) that attaches to your blower. Their thermostats integrate nicely with HA, and even can integrate on their own with an Awair sensor to turn on air cleaning. P.S. I have both. Very happy.

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.

We built one from a kit, and it works great. It uses furnace filters. Our PM 2.5 was around 40 in our apartment. (The PM 2.5 outdoors in my city is currently around 160.) After running the air purifier for a couple hours, it's down to 5. [https://www.cleanairkits.com/](https://www.cleanairkits.com/)

Assembly was easy, and it will be easy to change the filters. Supposedly you only need to change the filters once or twice a year.

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

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

Because of the added surface area of the 4x filters in a corsi rosenthal setup, filter changes occur much less frequently. You’re talking 5-6 months so your cost estimations are way off there.

Then let’s also factor in how they’re more effective, more repairable, less upfront cost, and will be eternally supported as you’ll always be able to buy furnace filters and a box fan. I do agree that over the long run they’re not more cost effective (assuming companies continue to make filters for their products) but they’re still the better option

Nah it’s not subjective. Tests have been performed and CR is truly the more effective option. You’re acting like applying duct tape involves an engineering degree. One of the aforementioned [tests](https://www.rtings.com/air-purifier/learn/air-purifier-performance)

Have you heard of Corsi-Rosenthal boxes? They are DIY (make it yourself) air purifiers, the basic model is a 20" box fan plus four furnace filters, with duct tape and cardboard to seal up the bottom and to cover up the corners of the fan. You can choose the level of filtration you want. Depending where you get your stuff you can maybe do it for under $100. Whichever you choose, pre-made purifier or CR box, make sure to note the cost of replacing filters and how often you will need to do so. From what I know, the 3M Filtrete furnace filters are best to use in CR boxes since they have the least airflow resistance. Whatever level of furnace filter you get, it's not going to be as good as HEPA (the top ones are close though) \*\*but\*\* CR boxes have a lot higher airflow than air purifiers, so the air can actually get more filtered since it goes through the filters more often. You can also add carbon (VOC/gases) filter layer to a CR box if you want, though they mostly are just particle filters because their popular use is to clean air of virus.

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/

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.

This is true. Web-search for a "Corsi-Rosenthal box." Actually more effective than most commercial air purifiers because it moves much more air. It's simply several MIRV-13 furnace filters taped to a cheap fan.

Two DIY Corsi-Rosenthal boxes. Better HEPA filtration than pricier air purifiers because they move much more air, hence more repetitions through the filters. Verified by research.

>I’ve done some research online There is a rabbit hole to go down comparing filter single pass capture-rates and clean air delivery rates. It is possible that a couple of [DIY Corsi-Rosenthal boxes](https://www.webmd.com/allergies/corsi-rosenthal-box) will be more effective, or more cost-effective, than a commercial HEPA filter. Especially for use while doing renovations that generate dust, Where we live, there are days when the AQI gets up to "Health alert: The risk of health effects is increased for everyone." and it is sometimes at "...members of sensitive groups may experience more serious health effects." for multiple days. We just replaced one of our Blueair air purifiers (under warranty). The replacement has a particulate counter that controls the motor when set to "auto". When we fry something on the stove-top -- two rooms and two closed doors away -- it sounds like it is trying to get up to airspeed. I know the Blueair makes difference in the way things *smell* on days when the air outside is purple, so it is not completely ineffective. OTOH, the two Blueair purifiers are on all the time and we have ***not*** noticed a decrease in the rate at which dust accumulates on the woodwork in the house. I've thought of getting an air-quality monitor to try to quantify the efficacy of the Blueair purifiers, but I am not sure what I would do with the information. I've got two double-tall Corsi-Rosenthal filters -- one in the Attic and one in the basement -- that I run when the air gets really bad or when I know I am going to be working in one of those spaces for a long time. The C-R boxes move a lot of air, and do really cut down on the big-enough-to-see dust circulating in the air and piling up on surfaces. * Eykelbosh, A. Do-it-yourself (DIY) air cleaners: Evidence on effectiveness and considerations for safe operation. Vancouver, BC: National Collaborating Centre for Environmental Health. 2023 Jan. [https://ncceh.ca/resources/evidence-reviews/do-it-yourself-diy-air-cleaners-evidence-effectiveness-and](https://ncceh.ca/resources/evidence-reviews/do-it-yourself-diy-air-cleaners-evidence-effectiveness-and) * Stephens B, Siegel JA. Ultrafine particle removal by residential heating, ventilating, and air-conditioning filters. Indoor Air. 2013 Dec;23(6):488-97. doi: 10.1111/ina.12045. Epub 2013 May 13. PMID: 23590456. [https://onlinelibrary.wiley.com/doi/10.1111/ina.12045](https://onlinelibrary.wiley.com/doi/10.1111/ina.12045) * Ratliff, K., & Gov. (2023). *Homeland Security Research EPA ORD’s Corsi-Rosenthal Box Bioaerosol Testing Results*. Retrieved February 15, 2025, from [https://today.uconn.edu/wp-content/uploads/2023/10/EPA-ORD-CR-Box-Bioaerosol-Results-embargoed-10-30-23-11am-est.pdf](https://today.uconn.edu/wp-content/uploads/2023/10/EPA-ORD-CR-Box-Bioaerosol-Results-embargoed-10-30-23-11am-est.pdf)

I built one yesterday for my garage. Didn't take long at all. Here are some more build designs for anyone who might try to make their own: https://cleanaircrew.org/box-fan-filters/

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.

throw a DYI CR box in there for $50-75 simply to be able to get a big volume of air cleaned quickly and cheaply in an emergency, especially if you are in the path of reoccurring wildfire smoke.

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.

Corsi Rosenthal Box: 1 Box fan, 4 merv 13 furnace filters, painters tape or duct tape, cardboard sheet for base. Alternate version, less efficient: 1 box fan, 1 furnace filter If you suffer from seasonal allergies or the recent wildfire smoke we've been having, I'd like to share a cheap DIY air purifier you can make that works just as good as a traditional air filter. Here's a video explaining how to build the "Corsi-Rosenthal" box: https://youtu.be/hIuH-2naozI?si=VLWPsGzxEPXHjfhy The 1 box fan, 1 furnace filter method: https://youtube.com/shorts/oTfJ7xI2ZE8?si=-A9Ud3UWwhbehReg I've been using my Corsi Rosenthal box since last fall and it's worked amazing.

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/

I think a DIY Corsi-Rosenthal box is the sign of someone frugal but serious about their indoor air quality

I have both, and appreciate the analysis, but the CR boxes just absolutely knock the pants off the Coway boxes for cleaning air at volume. For one, you won't need a CR box in every room. One will cover a lot more square feet than a Coway. I run both types of filters in my baby's room (paranoid overkill), and have used them for all sorts of things. I've ran the CR boxes in construction applications (they are SO GOOD for dusty construction), kitchen applications, offices, etc. and there's no way the Coway can keep up with the higher volumes. It will run at the highest setting and burn through filters. I'd never put a Coway in anything but a medium-sized room with very little demand for air cleaning - a bedroom, maybe a living room. HEPA filters @ 16x20 are usually way less than $120 for 4 - I'm usually around $80 to $60. Buy them in bulk and it's no problem. One roll of duct tape will last you for a very, very long time for a CR box. The fans run indefinitely - easily 5 years. I have yet to replace one. Ultimately, look, either way is fine, they'll be far superior to nothing. But I don't think the Coways compare to the blend of value and ease that the CR offers. Maybe not everyone agrees. That's just how it's worked in my experience.

For a super budget-friendly option, you could even just build a Corsi-Rosenthal box. It's a surprisingly effective DIY

CR box, probably.

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 :)

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.

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.

Look up corsi-rosenthal boxes. I just built one last week and I'm way happier with it than my levoit.

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.

Depending on where you are you can spend way less and get good stuff. It really depends on how dirty the air is and how clean you want it. **H**(igh)**E**(fficiency)**P**(articulate)**A**(ir) filters are good because they capture more particles than others. Below them are MERV filters rated 1-16, and [as you can see here](https://www.epa.gov/indoor-air-quality-iaq/what-merv-rating) anything less than 12 nabs under 80% of PM2.5 and imo isn't worth it. These are also more common in home HVAC from what I've seen as well - for mobile units, it's either HEPA or "HEPA-type" which means nothing. If you want the most efficient unit and to spend next to no money, [Corsi-Rosenthal boxes](https://corsirosenthalfoundation.org/instructions/) are the way to go - you need to be able to build and rebuild them, and tolerate a decent amount of noise though. Otherwise, the size of your rooms matters. BlueAir, Coway, Honeywell, Lasko/GermGuardian, Levoit, and Smart Air are some brands that are reputable and have a range of units and sizes. Keep in mind most purifier marketing advertises performance on only the **highest** setting, while advertising noise on the **lowest** setting. Most makers do not have data on other settings, though there are rare exceptions [like Medify](https://medifyair.com/collections/air-purifiers/products/medify-ma-40?variant=39663322628163).

The best? Really? You really want the best? Here you go: https://aghealth.ucdavis.edu/news/corsi-rosenthal-box-diy-box-fan-air-filter-covid-19-and-wildfire-smoke this is the absolute best air purifier, backed by science. And cheap too. I have one too.

You want something genuinely good and cheap? Make a Corsi-Rosenthal Box or two.

If you don’t have an air purifier you can make a corsi rosenthal box for cheap. Or you can make a more efficient one using pc fans (we have one of those. They are super quiet, super cheap to run and the filters only need to be changed every 6 months or so. Plus we can get them for cheap when they go on sale). It makes a load of difference in air quality.

The Corsi-Rosenthal box is a fabulous option for folks on a budget. It works great and literally saved lives during the thick of the pandemic (you need a higher rated air filter for removing viruses). You want to balance air flow with filtration. Obviously the higher the filter rating, the harder the fan is going to have to work to pull air through, so you want to use the lowest rating for the stuff you want to filter out: MERV 8 is good for regular dust/pet dander, pollen; MERV 10 will catch smoke particles; MERV 13 is going to filter out virus sized particles. Also $$ for higher ratings. Some filter shapes are more expensive than others, but you can use corrugated cardboard (apartment building recycle bin, or liquor store for good free cardboard) and tape to fill in gaps and make the cheapest filters work.

I built a Corsi-Rosenthal box for $60. It doesn't look pretty but it works really well for our small house at that price range. 

Try a Corsi-Rosenthal box first. See if it makes an impact in your house. Then invest in a proper air purifier that is sized to process the air volume of your house at least 3-4 times a day

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.

Yep, the only right answer. https://corsirosenthalfoundation.org/instructions/

A box fan, tape, and a MERV 13 furnace air filter. Really! [Tutorial on how to create the filter from the University of Michigan](https://youtu.be/kH5APw_SLUU?si=RlMVyuw7oxgbx8cZ) A bit more of an advanced “model”: the [Corsi-Rosenthal box](https://en.wikipedia.org/wiki/Corsi%E2%80%93Rosenthal_Box) [Study done on different versions of the diy air purifiers](https://ncceh.ca/resources/evidence-reviews/do-it-yourself-diy-air-cleaners-evidence-effectiveness-and) Anecdotally, I made one of these for less than 35$ and within days it cleared up my cat’s allergies! I noticed a big improvement in air quality, especially during the dry seasons while living in the desert.

I love the ugly-ass Honeywell tower one i have. You can get washable filters too, which is a nice money saver. It's relatively quiet and powerful. Everyone should make at least one Corsi-Rosenthal box though because they are super effective!

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

Anything with a HEPA filter and appropriate CADR for the space it's being used in will work. Corsi-Rosenthal boxes (made out of box fans and furnace filters) are pretty cost-effective and perform really well.

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

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.

I've had quite a few air purifiers, most fans use bearings and bearings will eventually fail. I've had one purifier that's 7 years old and still running, but another failed after 2-3 years. I'm switching my air purifiers from Hepa to Corsi-Rosenthal boxes, though I'll probably still use small hepas in critical rooms but not sure. I'm looking at Clean Air Kits, 3D Handyman, AirFanta, or the NuKit Tempest. Corsi-Rosenthal boxes use Merv 13 or higher HVAC filters and usually a box fan, but people also use PC fans. Here's why this is a better choice for people who want to buy it for life. 1: PC fans and Box fans are made by dozens of different brands and can be purchased anywhere - Walmart, Amazon, Home Depot etc. 2: HVAC filters are cheap, efficient, and abundant. 3. These purifiers do not lock you into one brand and all parts are user replaceable. 4: Efficiency - because the filters are more efficient, it requires less energy to pull air through them. PC fans use DC motors, which use 1/10 of the energy and are much quieter than AC motors. They're also are engineered to be virtually silent. HVAC filters benefit from economies of scale and are cheap to replace. Since the whole system is made from replaceable parts, you won't ever have to throw it all away just because a model got discontinued or a brand went out of business. Many people think HEPA is the gold standard and there is no doubt if sized appropriately they filter air quite well. The problem is to get them to work you need to either run them at full speed all day or buy a huge and expensive unit that you can run at half speed to get a reasonable CADR. Surprisingly, data shows that Corsi-Rosenthal boxes are just about as good and that's because they can achieve higher CADRs, and a greater number of Air Changes Per Hour. The filters do not clog as quickly and can filter large volumes of air quietly which means you will leave them running all day. To get the same amount of air cleaning power one unit achieved with my winix 5200-2 I'd have to run it at turbo mode and it's just way too loud. Plus the corsi rose thal box built with pc fans pulled 8 watts vs the winix pulling about 60 at turbo. My electricity rates in CA are super expensive and it saves hundreds of dollars a year in energy and filter costs to go with a Corsi Rosenthal box. This is the video that convinced me this was the way to go: https://youtu.be/gaQTYrisieA?feature=shared Air filters are really just extra insurance - you'll do a lot more good with a solid Hepa vacuum cleaner and frequent vacuuming, as well as keeping up with your HVAC system's filter changes. You should run your HVAC fan a few hours a day to help filter massive volumes of air quickly.

Make a corsi rosenthal! It can really help.