The Best Air Purifier Is A $150 DIY Option

The Corsi-Rosenthal box is the best air purifier we've tested—and it's one we built ourselves. We're saying that having tested 26 in total. Just how can this ugly, loud, extremely DIY box of filters be the BEST air purifier when we've got some sleek Dysons, portable Levoits, and much prettier, cooler boxes of filters?

Chapters:
00:00 Intro
00:37 What is a Corsi-Rosenthal Box?
04:40 How We Test Air Purifiers
07:35 Air Purifiers In Action
08:45 Conclusion

For more details about our testing process, check out our article:

Follow Us:

[Beregorn]

Physicist here: I'm a great fan of your work, and you have become my reference when buying and suggesting monitors. The work you did here is quite interesting, but the methodology can be improved.
First of all, I would wait 5 minutes between the introduction of the smoke and the moment you start the machines: this way the smoke can spread uniformely in the room and the results are less affected by the way the smoke enter into the room. In addition, you would also have a more accurate reading of the starting amount of particles, which you should use to normalize the results.
Last, but not least, every time you perform ANY kind of measurement, you should repeat it at least 3 times (or even better 5): the first measurement gives you a value, the second one tells you the accuracy, the third one tells you wether the difference between the two is due to stochastic noise, or you have some problems in your methodology. Of course, the more measures the better, but you need to balance the accuracy of the measure with the time you are willing to spend, and 3 measures are usually enough to know if you need more. In addition, would be nice to see if 3 or 5 puff of smoke are enough to see a drop in the performances, giving you an idea of how long the filter would last

[crazylego]

You guys really came out with this one day after I purchased an air purifier from Ikea

[KaledTV]

Following their toaster PhD study, they come to deliver another unexpected banger.

[SubFlow]

As a hobby mycologist, I make all of my own laminar flow hoods. They work great for a fraction of the cost of a commercial brand.

[LittIegator]

I've seen people use PC fans instead of box fans. There is also at least one company that makes fancy schmancy looking frames for Corsi Rosenthal boxes that don't look like actual trash.

[emmamitchell]

I would love to see some testing with 120mm computer fans strapped to a filter. They are optimized for static pressure to push air through radiators. I would recommend a push configuration versus a pull configuration, but testing both would be great. A cheap fan would be the arctic P12. If you use the PWM version they are even speed controllable. A high end option would be the Noctua NF-A12X25.

[Barnacules]

I've literally been doing this for many years now! And I didn't invent it, someone told me to do this that had also been doing it for many years. Also, if you have a forced air system in your house just find the cold air intake and place these filters over it and tape them in place to seal all the holes around them and it will also clean the smoke and other particulate out of the air of your entire house. We did both of these things for many years during the wildfire seasons because without it the house would be filled with a haze and our throats would be on fire. Also, it's not necessary to use 4 filters unless you need the capacity. Even a single filter the same size as the box fan taped to the back of it (intake) will work great for several weeks even with heavily contaminated air before it's clogged up and needs to be changed. We break these out every year during the wildfire season here in Washington State because without it our throats feel like they are on fire and our eyes burn. People have been doing this for a very long time though.

PS: Credit to Adam (aka. KevlarCondom) for buying me a box fan and my first Hepa filter showing me this technique a long time ago.

[uguraktas]

Please test the CR box with Pc fans! they are much quieter and consume way less power. You should be able to find more about them easily. The 5 fan and 9 fan versions are very popular. They usually use arctic p12 fans. There are also companies selling cr inspired air filters with pc fans. One of them is Clear Air Kits. Regardless, its a very good video!

[m-ax]

would have been nice to see a comparison with one of the bigger units (eg. iQair healthpro) that would be more similar to the dyi solution in terms of ugliness and footprint.

[ChristianBehnke]

If you buy the pack of filters at Costco for $40, adding a $30 box fan can make the CR box build cost far below what you quoted in the video.

[LurkerPatrol]

I been sneezing my buns off in my bedroom, and now I'm considering making the ugly boy, thanks guys!

[carljones]

There was a guy in China, before the covid pandemic, doing his PhD research on this, basically showing that HEPA filters attached to box fans are better air purifiers than multi-thousand dollar units. I wish I could find his work again, but it has been basically impossible since covid. Seems like Corsi and Rosenthal beat him to publication.

[David.Elfstrom]

Whoops - the particle counts start at WAY over the count limit of the meter you're using. It's missing many of them at the start. This is visible in how it takes until below 100, 000/L before the drawdown on the log scale vs time plot becomes linear. It also means the natural decay isn't representative of the actual natural decay. Is the data available for download? What is the size of the room used?

[khawajadotd]

There are prettier designs available from "The 3d handyman" youtube channel. He has also done testing on a bunch of filters and fans, and found large differences between brands.

[TheStaniG]

I subbed for a hp laser printer review amd now not only has your TV testing been INCREDIBLE but you come up with these BANGERS I didnt even know I needed.

[edwardhsieh]

You guys make me want to work at rtings.

[adriankoch]

The better DIY alternative to the box fan design uses a bunch 120 or 140mm high static pressure PC fans. Uses the same filters. Cheap to build, cheap to run (pc fans use <10w each), good flow rate and very quiet and you can use off the shelf components to adjust the fan speed depending on time of day or other reasons.

[crimson]

If you're going to position the air purifier in a corner like shown, would it make a measurable difference for the corsi rosenthal box if you only have the two "exposed" sides with filters and just a mesh on the sides facing the walls?

[nottimothy]

Would be great to also compare replacement filter costs and expected lifetime. The more filter surface area (given a fixed volume of air being filtered), the longer the filter will last. Of course the finer the filter, the shorter it will last. Some manufacturers go with the razor and blades model, and make minimal margin on the purifier and extreme margin on the filters.

[ianchoi]

I made one of these for our class room a few years ago, we're a project based school so we be doing alot of weird plant and chemical stuff which made the room stink. So I got approval from our teacher to build one and it worked amazingly.