CleanAirKits - Corsi-Rosenthal Box

I have several air purifiers and my favourite is a PC fan air purifier from North Box. There are various ones on the market but [North Box is Canadian](https://aidankepo.wixsite.com/northboxsystems). It's available directly from their site or through [Donate A Mask](https://shop.evidencebased.ca/collections/cr-boxes-air-purification). What's nice about PC fan air purifiers is that they're really quiet, quite effective and don't rely on proprietary air filters.

As u/ZedZabeth mentioned, making a Corsi Rosenthal box is a good idea. If you can afford it, a PC fan air purifier uses very little energy, is quiet and takes up less space than a classic CR box. If money is really tight, a respirator mask is probably the easiest, most accessible and cheapest solution. I know the prospect of masking at home is unappealing, but even masking from time to time indoors will lower your exposure.

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/

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)

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 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/

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 absolutely. I don't mind a little noise, but on some of these air purifiers to get the CADR that makes sense, you need to blast them. I recently bought a PC fan air purifier from clean air kits. They t won't win any beauty contests but it moves a tremendous amount of air with very little noise.

Try a [box fan air purifier](https://www.reddit.com/r/crboxes/comments/1hi3z6h/portable_box_fan_air_purifier_with_shroud/). (Bone up on Corsi Rosenthal boxes.) My box fan air purifier is just as effective as some commercial air purifiers that are at least 10 times more expensive. You can use the savings to build more air purifiers. If you want a quiet and powerful air purifier, try something from [Clean Air Kits](https://www.cleanairkits.com/). The Brisk Box Kits, Luggables, and Tower of Power use furnace air filters instead of special proprietary air filters. Furnace air filters are widely available at reasonable cost due to competition and economies of scale.

Corsi-Rosenthal box. Many people love them on this sub, if done right. They're great! Although I believe you'll want a MERV-13 at a minimum. :)

Three words. Corsi Rosenthal Box.

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

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.

A commercial air purifier that meets all your criteria and actually works as effectively as you want it to will be well over $300. Under $300 you only have two realistic options: build yourself a Corsi-Rosenthal box with computer fans, or buy a Corsi-Rosenthal kit. A CR box with computer fans is going to be quieter than any commercial air purifier, and the filters will be cheaper because they're standard filters you can buy at any hardware store instead of proprietary filters you can only buy from one company, and by design CR boxes are super easy to maintain. CleanAirKits in the US, NorthBox in Canada, and Nukit in China all sell CR box kits with computer fans. The most BIFL option out of these is Nukit, made with steel, while the others are made with wood or acrylic. I have severe allergies myself and I have two CR boxes, a large one I built myself at home, and a small portable one from CleanAirKits for my office or wherever else I might need it. They've made a big difference in my allergy symptoms. Check out the Nukit Tempest mk 2 when it releases later this year, it is planned to have all the features you listed. The other thing with allergies that often gets overlooked is cleaning. Especially if you have pets you are allergic to, you should dust and vacuum your house two or three times a week. Air purifiers alone won't be enough.

Corsi Rosenthal box. Fuck proprietary (and often expensive) filters. Mine are from Clean Air Kits and they are stupid quiet, I can run them off a battery pack in case of power outages cause they are super cheap in terms of power usage and I can get furnace filters cheap. We have two dogs (one of whom has nasty allergies to pollen) and they make a huge difference. We have one per floor but make sure they are sized for your space.

>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)

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.

As u/ZedZabeth mentioned, making a Corsi Rosenthal box is a good idea. If you can afford it, a PC fan air purifier uses very little energy, is quiet and takes up less space than a classic CR box. If money is really tight, a respirator mask is probably the easiest, most accessible and cheapest solution. I know the prospect of masking at home is unappealing, but even masking from time to time indoors will lower your exposure.

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).

You can make a Corsi Rosenthal air filter. Check out the instructions on youtube. They work as well as industrial air filters.

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.

Coris rosenthal or the Coway filters. Don't just run them now, run them all the time. Great way to remove dust, allergens, and viruses from the air.

Have you considered making your own? https://en.m.wikipedia.org/wiki/Corsi%E2%80%93Rosenthal_Box I know some people are hesitant because of the looks. But I've been using this design since COVID and I can't be happier. The box fan was $20 and the filters are $40 every couple of months. They're inexpensive and you can use any size filter you like. So the only real downside is the aesthetics are not what a lot of people are looking for. But it works pretty dang good with the right filter.

The only viable option for affordability short term and long term.

If you look at cost, CADR/CFM, and noise, nothing on the market beats [Clean Air Kits](https://www.cleanairkits.com/?ref=CCCircle), period. Data to back it up, any entry in gray is a setting that is louder than 50db: [https://docs.google.com/spreadsheets/d/1kQMWNyKfkB0K8A4\_yXMrSAb-CruVl9lASJEpLGLtS8o/edit?usp=sharing](https://docs.google.com/spreadsheets/d/1kQMWNyKfkB0K8A4_yXMrSAb-CruVl9lASJEpLGLtS8o/edit?usp=sharing)

A [CR box](https://corsirosenthalfoundation.org/instructions/) (Filtrate 1900 or MERV 13 furnace filters and a box fan) is your best option: they're cheaper and more efficient than commercial air filters; because the filters are just furnace filters, you can get them basically anywhere; and they can be designed in lots of ways to suit your space (the standard 4-filter design, two filters in a triangle shape with the fan as the third side, one filter with a spacer between the fan and filter, two or four filters with computer fans for quieter filtration, mounted to a wall like a floating shelf, etc). Look online for pictures and further instructions for different shapes.

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

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

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.

I made it, just crudely taping some whole house filters onto a box fan. It won't be fun to tape up again when I need to replace the filters, I need to create a proper design that's easily maintained, but this was a proof of concept. It's been several months and it works perfectly.