The Best Air Purifier Is A $150 DIY Option

[@Beregorn88]

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

[@kidShibuya]

You have made the assumption that they don't do this already. You know that how?

[@TonyOstrich]

​@@kidShibuyago away

[@Demigirlboss]

While the point about waiting five minutes is a good one, and pretty fair, I do think it's worth considering that having the purifiers on _while the smoke propagates_ helps determine the quality of the fans, since, as we saw in with the Dyson bladeless, some of them can actually prevent air from passing through the filters, and in this particular test that's a really useful data point to have in order to determine just _why_ certain purifiers which should have a significantly higher theoretical performance don't reflect that in practice. Regarding the multiple tests, that's standard M.O for any kind of technical testing as far as I'm aware, it just seldom gets brought up unless explicitly relevant because it's so well-known that in most cases it'd be comparable to dead air. That said, I don't think anyone who's working on doing analytics like this professionally is just doing one testing pass and calling it a day, which is a big contributor to why testing things like this can be very expensive and time-consuming, and a big reason why you should go give RTINGS your money, because they do good work!

[@Beregorn88]

@@Demigirlboss when they described the monitor tests they specified the number of repeated tests and how they combined the results; here they didn't say anything about this, nor did they mention it on the article on the website. They didn't even mention a variability from test to test, which is VERY indicative of just one test being performed... The 5 minutes delay has 2 different functions: having all the system starting in more uniform conditions, and being able to accurately record said conditions, in order to remove any leftover difference during the analysis.

[@CanIHasThisName]

Christ, mate you’re not doing a public lecture, why the pretentious writeup?

[@crazylego98]

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

[@RTINGScomRD]

There's still time to return! 😂

[@AllisonRoadWest]

You got ripped off. Plus these builds are often better for your energy bills and vastly more efficient depending on fan purchases. Thus over 4 or 5 years IKEA will rip you off even more. Return it quickly 🎉

[@ThePwig]

This has been known for a few years, ever since Covid.

[@HanmaHeiro]

@@ThePwig But not widely known, I'd say

[@lemon9.9]

@@HanmaHeiro I searched for air filter comparison on youtube before and this design came up almost immediately

[@KaledTV]

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

[@RTINGScomRD]

Hahaha we always try to deliver, thanks for watching! 😄

[@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.

[@RTINGScomRD]

Even better! It seems that pricing is different depending on where you are in the world!

[@ChristianBehnke]

@@Weaver_Games Actually, je suis 🇨🇦, and yes, you can find the components for cheap.

[@homemini9254]

Yes. Cheaper

[@RennieAsh]

@@ChristianBehnke je ne veux pas le Canada XD

[@r_bear]

The crazy thing about the Costco pricing is that it's like $45 regardless of what size you get-16x20? 16x25? 20x30 even? Same price!

[@SubFlow22]

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.

[@tsmith6210]

Please tell me how you make it. I really need it for basements

[@m-ax729]

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.

[@HanmaHeiro]

Take a look at their site. If it's not there yet, it could be in the future!

[@yarkee8128]

I imagine clean air stars filter recommendation tool, or housefresh would also have similar data

[@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.

[@Peace22_]

Hey Barnacules, you mentioned it's not necessary to use 4 filters unless you need the capacity, and also mentioned your use of HEPA filters. They did speak on both of these topics in the video as well. They said they didn't use HEPA filters in their testing because apparently a much stronger fan would be needed to overcome the extra resistance, and they also discussed that using only one filter strapped to a fan dramatically decreased the effectiveness of the filtration. Seems like if you want the best value it makes most sense to do the 4 filter box method. I feel like the HEPA filter should still do a really good job even with a box fan though.

[@tyscam]

Strapping one of these filters to a fan is ineffective. You do not want to force air across them, you want negative pressure to pull air through them. You still need to build the box in other words, just that 3 sides can be solid.

[@Cujobob]

@@tyscam you can strap a 3” filter to a fan and get decent results, but not to the same level of performance as a full box.

[@jotch_7627]

​@@tyscamokay, then strap it to the side of the fan that generates negative pressure. fans arent magic, they dont "force air" through anything. they work via pressure differentials just like anything else

[@vincentrobinette1507]

Box fans don't do well with the head pressure of a single filter. Using 4 or 5 filters really does improve airflow volume compared to noise, and, since each filter only has to allow 1/4-1/5 the airflow of a single filter, you can get much more use out of each filter before replacing them. In the long run, it's much more economical as well as effective, to build a full Corse-Rosenthal box, than to tape a single filter to the back of a fan.

[@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.

[@Zinic_]

Yeah mine is in the mail and I'm going to use it as a template to make my own out of plywood.

[@Jaker788]

And PC fans are almost all brushless DC motors (3 phase AC synchronous). Those types of motors are in the range of 90% efficient, while most AC powered fans use a shaded pole motor which is around 20% efficient. If you don't want to use PC fans and want the ease of one fan for the filter box, you can look up brushless DC fan and brands like Vornado have one. The Vornado brushless DC fan is a bit over $100, more expensive, but also 70-80% more efficient than their standard fans and other fans using shaded pole motors.

[@meatbyproducts]

A box is simple to build out of scrap wood. My father built one of these in the 80s and made a nice frame for it and my mom could swap the filters with ease.

[@AJolly]

Yeah, I'd love to see rtings test the clean air kit PC fan based products instead

[@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?

[@uguraktas8018]

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!

[@adriankoch964]

This! The reaon for Arctic p12 is that they offer high static pressure. Using models with low static pressure (i.e high flow or silent variants) will have worse results, since those will struggle to overcome the filter resistance.

[@MY-qi8wq]

@@adriankoch964 Arctic P12/P14 is good, but not because of "high static pressure", but that they are cheap and offer high noise-normalized performance against a wide range of resistance. In fact, the entire reason why CR boxes work so well is that they have 1. absolutely humongous filter surface area and 2. filter material with lower resistance, which makes resistance extremely low. (The lower air velocity through filters also boost filter efficiency far beyond the "75%" quoted on the box.) Thus, with properly chosen filters, the so-called "airflow" fans can work well (e.g. box fans!), though the most efficient PC fan designs nowadays are all-rounders that perform well across a wide range, instead of "airflow" or "static pressure" optimized. Yes this includes Arctic P-series (despite being marketed as "pressure fans").

[@YouTrolol]

I bought 4x noctua 200mm fans and an ac fan splitter that split into the 4 connections. I like it, a lot quieter than the box fan I have, but I feel like the fans are too quiet. on max setting they're really quiet, so I wish I had higher airflow fans even if noisier, because I could always turn them down, not up.

[@MY-qi8wq]

@@adriankoch964 Arctic P12/P14 is good, but not because of "high static pressure", but that they are cheap and offer high noise-normalized performance against a wide range of resistance. In fact, the entire reason why CR boxes work so well is that they have 1. absolutely huge filter surface area and 2. filter material with lower resistance, which makes resistance extremely low. (The lower air velocity through filters also boost filter efficiency far beyond the "75%" quoted on the box.) Thus, with properly chosen filters, the so-called "airflow" fans can work well (e.g. box fans!), though the most efficient PC fan designs nowadays are all-rounders that perform well across a wide range, instead of "airflow" or "static pressure" optimized. Yes this includes Arctic P-series (despite being marketed as "pressure fans").

[@MY-qi8wq]

@@adriankoch964 Arctic P12/P14 are indeed very good, though not because of "high static pressure", but that they are cheap and offer high noise-normalized airflow against a wide range of resistance. In fact, the entire reason why CR boxes work so well is that they have 1. huge filter surface area and 2. filter material with lower resistance, which makes resistance very low. (The lower air velocity through filters also boosts filter efficiency far beyond the "75%" quoted on the box.) Thus, with properly chosen filters, even so-called "airflow" fans can work well (e.g. box fans!) Do note however that the most efficient PC fan designs nowadays are all-rounders that perform well across a wide range of resistance, instead of "airflow" or "static pressure" optimized. Yes this includes Arctic P-series (despite being marketed as "pressure fans")!

[@LurkerPatrol]

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

[@weslusk3798]

You might also want to check out Clean Air Kits.

[@RTINGScomRD]

Glad to hear we've been a good inspiration! 😄

[@adriankoch964]

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

[@3nertia]

How many fans does that require and do you have any references for your claims?

[@hotdogsarepropaganda]

@@3nertia its all about CFMs and how much pressure they have. the best PC fans for pressure and CFM are 120mm Artic P12 max or Artic p14 max for 140mm. they come in 5 packs for aound 35-45 bucks. the standard CFMs for a box fan is 1100-2500 for low and high. the p12max is 86 cfm per fan the p14 max are 95. so it would take roughly 11-12 (12 to make a perfect square) 14mm fans to equal the CFM of a box fan on low. there is not good static pressure information on box fans. the cost would be 3 boxes at 45 dollars each so 150. they might use less power around 100w and may be quieter because of blade tip surface area but the noise will also have a different and likely higher pitch than the box fan. the p14max fans are designed to push air through small gaps in computer liquid cooler radiators and may yield an advantage in pushing through the filters but wont be directly comparable without static pressure ratings from box fans

[@TheEchelon]

@@3nertia Googling will give you all the results... "DIY pc fan MERV air purifier"

[@Cujobob]

@@3nertiaa few brands sell kits based around this idea if you’re curious. Two are Nukit and Clean Air Kits.

[@MH-kc5jr]

10W for a pc fan even at full power is too much, more like 6-7W at max

[@nottimothy5994]

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.

[@zncon]

The homemade box would win across the board. Furnace filters are made in such massive quantity that nothing custom for a purifier is going to beat that economy of scale. You can also buy the filters in large 10+ packs which knocks the price down even further. I have no idea how they managed to spend $200 to make that box though, the fan shouldn't cost more then $30, and the filters are around $25 each if you buy them at full retail price.

[@Weaver_Games]

@@zncon Everything in Canada is ridiculously expensive, you have no idea.

[@gg-gn3re]

@@zncon They also came up with the idea that this was invented during covid by 2 engineers and not like 100 years ago. Tons of youtube videos of these designs predate covid lmao.

[@zncon]

@@gg-gn3re Oh boy that's a whole separate rant that I wasn't going to get into, but I hate that two people just slapped their names on what has been a known 'box fan hack' for decades.

[@gg-gn3re]

@@zncon Yea I have a wooden one with 3 slots for filters and wheels on the bottom, hard top (so I use it as a table) and a blower/ air mover fan inside. Way higher static pressure/vacuum/air flow... and it's like 15 years old lol

[@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.

[@CaveyMoth]

I got his design that uses a 12" in-line fan, and added a secondary activated carbon filter inside. This thing is bananas. The fan is almost scary how powerful it is.

[@marceline8488]

​@@CaveyMothThe AC infinity fan?

[@cajonesalt0191]

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.

[@tristanwegner]

sound like you are talking about the SmartAir blog

[@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.

[@emmamitchell1582]

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.

[@r_bear]

price-wise you can also do (say) P14 PWM PST. One cheap voltage controller will control all of their speeds, and (140/120)^2 = (7/6)^2 =1.361x more airflow for a given speed, so you can either run them quieter or faster!

[@Karim-ik5ij]

Check out clean air Kits. They do exactly this.

[@Mischievous_Moth]

I do a little woodworking, and you know... I could probably build a frame for one of these so the filters can be replaced more easily. Might even be able to SPRUCE it up a little! (Good ol' woodworking puns)

[@_ch1pset]

there's another aspect not discussed, energy consumption. Box fans use axial fans, while most purifiers run on centrifugal fans. Centrifugal fans generate more pressure for a lower power consumption compared to an axial fan the same size. Sure, it's less air flow, but you really need that pressure to push air through the filter. The box fan contraption also has the downside of requiring 4 or 5 air filters that all need to be replaced at once, essentially you have to build an entirely new one each time you change out the filters. That's like $300 a year minimum. It's NOT necessarily cheaper.

[@WatsitTooyah]

Multiple filters in an environment will make them overall last longer. You have the same amount of contaminants in a duration of time wether you have 1 filter or 100. Changing them on a strict time frame can be a big waste. Every environment is unique. Also definitely true about the power consumption compared to typical purifier designs

[@3nertia]

Centrifugal fans are also about 3x more expensive on average, if you want to buy them in small quantities anyway heh

[@motley06]

If you’re burning through $300 worth of filters in this design, you’ve got other issues going on

[@_ch1pset]

@@motley06 if you only need something temporary with how well it works, I think you need to ask yourself why $150 is justified in the first place. Air purifiers are needed in environments where the extra filtration is needed. Chances are, if you have an air purifier, you are running it 24/7 or every day, consistently for months or years at a time. It is not unreasonable to replace the filters once every 6 months. This test doesn't take into account the long-term cost effectiveness of these units or this design. MERV13/HEPA filters are not super cheap, and running the units for long periods of time consumes a lot of energy.

[@thePavuk]

In my country (center of Europe) single one of these filters cost about $70-100... Just saying. There are cheap on amazon, but they don't ship them here or after adding shipping and tax you are back to 70-100.

[@Zaf9670]

I’m curious about the PC fan versions of the DIY air purifier as well. Really surprised someone hasn’t done up an ESP32 controlled version for basic stuff like timers, ambient lighting, or other “make it nicer” features.

[@r_bear]

people have DIY'd them and folks like CleanAirKits (iirc) have added some features for niceness (aside from the nicer designs themselves), but it wouldn't surprise me to see them crop up in the future

[@njdotson]

That actually sounds like it would be a fun technology project. I wonder though if a small bedroom wouldn't even need that good of performance.

[@crimson293]

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?

[@r_bear]

This is true, but you only need about 4-5" of clearance to get ~100% airflow.

[@RajT-s5e]

Thank you, Rtings, for consistently delivering unbiased and data-driven reviews! I trust your recommendations completely and often make purchases based on your top lists without hesitation. I'm currently building my Corsi Rosenthal box, inspired by your guidance, as it's truly the best solution out there. For anyone looking to add extra functionality, consider using a smart plug for your fan setup. It allows for wireless controls like on/off switching or even scheduling - a small tweak that adds a lot of convenience. Keep up the amazing work!

[@Wireless_Gadgets]

I have Chinchillas in a tower cage, they take dust baths and shed fine fur all the time. I built this fan filter 3 years ago and see actual results and can breathe so much better. I have my fan filter near the HVAC air return vent so my HVAC can work more efficiently. I have run the fan 24/7 for last 3 years and replace filters every 3 months.

[@Bulldawzer]

Why didn't you mention using quiet PC case fans to solve the noise issue while maintaining same or higher CFM than a box fan?

[@fuxseb]

Computer fans create only a very low pressure, especially the quiet, low RPM ones. Their CFM figure is valid only at zero resistance. Add a filter and the flow is almost at a standstill. Obviously there are some stronger ones used e.g. in servers, but their noise profile and level is something between a hairdryer and industrial vacuum cleaner. They're not intended for use in inhabited rooms, which may imply legal liability, should someone damage their hearing or cut their fingers on the blades. A box fan on the contrary will have all required certifications and safety features.

[@tychay]

⁠@@fuxseb And yet an array of artic or SickleFlow computer fans get better performance in tests at about 1/10 the wattage and much much lower decibels than a box fan. Maybe because computer fans are not all low speed and they're designed to create a static pressure while a box fan is designed to create a breeze? Plus these are not HEPA filters and there is a lot of surface area to them, so it doesn't require much pressure to get air flow. If you want to talk "like a vacuum cleaner" try some of these commercial HEPA air purifiers at the max setting they are advertising at: either they are loud as a vacuum cleaner or they don't do jack at filtering air (looking at you Dyson).

[@dallasgombash5381]

Get some $1 fiberglass filters to use as a prefilter(and swap them out often), it significantly increases the life the the expensive filters.

[@shubinternet]

You’re also not generating or monitoring for small enough smoke particles. You need to go down to 0.1 microns and smaller.

[@amb1gamermain22]

That would be a nice metric, but keep in mind those expensive mainstream "hepa" carbon activated etc air filters had much worse performance than the diy box. 0.1um won't add much to the conclusion if what is claimed to clean 0.1um (hepa) wasn't able to clean 10um effectively

[@ianchoi버디]

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.

[@jordanviray]

Too bad this design got named after Corsi and Rosenthal when Neil Comparetto was the inspiration for them. A couple things: how would 4" thick filters do vs the 1"? More filter media area means theoretically more airflow and the ability to run quieter or use smaller dimensions iso-CFM . Related to CFM would be different box fan types. There's an optimal static pressure and CFM fan for the best noise normalized filtration efficiency for a given MERV and it would be really cool if a review site could find that out.

[@dtemp132]

The problem with 4" filters is that they blow up the economics, they are WAY more expensive than 1" filters.

[@AhpgZfoc4s]

@@dtemp132 Maybe. The video is about the best performing air filter. The DIY box just happens to be fairly inexpensive. The main complaints are that it is loud and ugly. The ugly could be fixed pretty easily but the loud part offers a few possible avenues to look at like thicker filters for slower fan speed. Economics wise, a pack of 4 20x20x1 MERV 13 filters is $65. A pack of 4 20x20x4 MERV 12 filters (no MERV 13 available) is $108. I don't know what the area of the filter media is for the 4" filter. All else being the same, it should be quite a bit more which means lower pressure at a given CFM so you can run a fan at a lower speed. As well, they have the ability to hold much more dirt which means longer intervals between filter changes. So if the interval is twice as long, the economics is a wash. I would guess the interval is going to be over twice as long so the economics might be better. But I don't have any data to back that up. However, the 1" thick Filtrete 1900 has an unusually high number of pleats as Project Farm discovered. The static pressure drop is fairly high but the DIY box has an enormous amount of filtration area so it might not matter vs a single unit for a furnace fan. They might even get higher performance in the lowest number of small particles after an hour test if they used even finer media like the Filtrete 2800. They could compensate for the pressure drop by using 4 20x30" ones and even a 20x20 on the bottom with some legs for a 40% increase in surface area. Who knows, not worth testing for a regular guy but RTINGS routinely tests tens of thousands of dollars worth of TVs, monitors, printers etc so messing around with a couple hundred dollars worth of filters would make for an interesting review. To me, the key to getting it quieter would be to find a DC powered box fan though and seeing which one has offers the most filtration when normalized for noise. Box fans don't get the exotic technologies found in PC fans like liquid crystal polymers and exotic fan geometries but there might be some out there.

[@Zyxlian]

@@AhpgZfoc4s I was thinking about using a much quieter design by using 20cm PC DC fan instead of a box fan for just a bedroom. I would love to see some testing of this concept. Maybe even expanding to a 2x2 square of 20cm fans for a better surface area to noise balance if you did need a larger volume. Automating/monitoring it with a microcontroller would also get the benefits of the much more expensive mass market air purifiers as well.

[@jordanviray]

@@Zyxlian I think that would work. I had a watercooling radiator that used a 2x2 square of 20cm fans and it was very quiet. Plenty of fan controllers out there as well so I think that would be a winner!

[@dallasgombash5381]

You can, just isn't as efficient, but it's what I do

[@Cryowatt]

Why test an inch away from the wall? I'm pretty sure the devices I own all recommend about a foot from any surface.

[@NekoOverflow]

Right?! Like I don't think Dyson is ever going to win in terms of effectiveness per dollar, especially not their fan models. But my BP-03 specifically says to have it at least 3.5 feet away from the wall. I laughed out loud when I saw that recommendation because I live in a small place. However, keeping it around a foot away from the wall makes its turn over rate feel so much better. If someone spends $1K on an air purifier, I think there's a good chance they're not going to shove it in a corner with a single inch away from the wall. The machine has wheels for goodness sake! Sure, 3.5 feet away from the wall is a ridiculous request for a consumer, so probably not follow the manual to the letter. But I would have liked to see them test a reasonable middle ground!

[@tyscam]

If you're going to just shove it in the corner, you really only need two filters.

[@jp23x]

true, but then again you can also just turn the box around and have 2 fresh filters after some time

[@chronickat5453]

one thing that would be good to consider is how expensive replacement filters are, especially the proprietary ones.

[@Collin_J]

The name-brand ones for the Coway air purifier I bought during COVID are $60. For a 1-inch HEPA filter. That's something like a 300-400% markup

[@edwardhsieh4644]

You guys make me want to work at rtings.

[@TheBautistrg]

You guys made this at the precise time. You just saved me so much money.

[@vincentrobinette1507]

A true "Corsi-rosenthal box has 5 filters, with a 20X20 filter built into the bottom of it. They are usually placed on a grid like stand, spacing them a few inches off the ground, to allow airflow through the bottom filter. If you use a panel on the bottom, using only 4 filters, it's called a "Comparetto Cube". (named after Neil Comparetto) Using the extra filter extends the life of each filter, allowing each one to trap more dust, before needing to be replaced. The extra filter area also allows the use of higher MERV rated filters, without the worry of being too restrictive. I typically build mine, using a 20X20 MERV 13 filter on the bottom, and build the sides using 20X25 filters. That gives an extra 400 Sq.In. of frame area, which is like having 6 20X20 filters.

[@jon_escamilla_]

I would love to see reviews of some of Blue Air's purifiers. Their purifiers don't have housings but a washable cloth surrounding a ring of a filter. These could be in that middle ground of presentation and performance. Either way, excellent work with the video and testing!

[@yarkee8128]

Alot of blue air filters use an ioniser to game the calculated card in manufacturer testing, and it tends to produce ozone which can be bad for long term respiratory health

[@bassgasmask]

for the single filter version, would it help using a thicker filter like a 4 or 5 in one?

[@gcs8]

There is a smaller version that someone on KZbin built that is as effective* using a 10-speed acinfinity fan and made some improvements to make it more serviceable.

[@mfs-ness]

Ikea makes a purifier built into a small table (STARKVIND), which makes it easier to have near the middle of the room.

[@mz1929]

how is the rosenthal box any better than just the homes Air Intake with the same filter/s...? weather the home has just 1 main central intake, or mini intakes in each room as well.

[@Collin_J]

I have yet to live in an apartment that uses a furnace.

[@dlewis9760]

@@Collin_J I live in a house heated by oil heat and hot water base boards. A couple of years ago I added a mini split AC/heat pump that cut the oil usage in half. Everyone is different. Why did you answer the question as some kind of flex? Neither you or I can answer the person's question. But it is a valid question.

[@EhNothing]

This is really neat, and I love the DIYness of it. As an exceptionally lazy person, I'd like the DIY option more if it could be built with a frame that the filters could sit in and more easily be replaced without having to fully retape the whole freaking thing just to replace filters.

[@Sashazur]

You can buy frame kits online. Search for “box fan air filter frame” etc

[@TruFalco]

That's what I was just thinking! Closest thing I've found on Etsy is box fan clips for 1 filter.

[@MrMoneyHelper]

Tape is cheap and makes a great seal.

[@catsspat]

I've been using DIY air filters using standard sized HVAC filters for many years. I buy a return filter grille made for HVAC, hack up a container for it and attach a fan to it. I've also built them using bathroom exhaust fans, like Panasonic models that are super quiet. I can then buy replacement filters at any home improvement store or even Costco.

[@user-Cata7sti7ma7]

you can get a bundle of 5 Arctic P12 Max fan for 50$ . wih a 10 buck controller. that could decrease the noise by alot and fine tune more since more control about fan speed.

[@adriankoch964]

Also use less electricity. Those box fans are around 100w. Wich adds up when running 24/7

[@JoelHernandez-tz3vk]

​@@adriankoch964Wonder how much of that inefficiency is due to the AC motor rather than the lack of static pressure.

[@Jaker788]

​@@JoelHernandez-tz3vkNearly all AC powered house fans use a shaded pole motor, those are just 20% efficient... PC fans use DC brushless, despite the name it's actually a 3 phase synchronous AC motor operated by PWM DC to replicate AC frequency. Synchronous AC motors are 90-95% efficient. You can also buy your standard home fans but with a brushless DC motor. Vornado has a model with one that claims 80% efficiency savings over standard fans. Vornado fans are also more pressure optimized than a box fan, partly because the housing is actually round so there's less air space around the blade and frame. Box fans are the worst option but still work. The main issue, regardless of motor choice, is the square frame. With that frame there's a lot of gap between the blade tips and it makes a lot of turbulent air blowback when there's resistance. The closer and tighter the blades are to the frame, the better your static pressure will generally be and a turbulence source is reduced. After that the remaining optimization is blade geometry and blade count to reduce turbulence between blades and optimize the noise frequency, there are trades to make in multiple ways.

[@r_bear]

Can get P14 PWM PST for only $40 or so, which have more airflow for a given sound level and can all be controlled via daisy chain with one power supply/controller.

[@P3z3r]

I kind of wish you orientated the box fan setup to blow air in the same direction as the commercially made air-purifiers.

[@samius1149]

It might be worth considering the 1 filter versions of this - which was the more popular version of this before Covid. Those are pretty effective too and with a far smaller footprint. Especially as with a smaller environment you can use a smaller 12 inch filter and regular 12 inch honeywell fan - which is pretty quiet and small. The filters need replacing more often but far less than 4x as often.

[@Collin_J]

I'm confused, didn't they do that?

[@XGD5layer]

They tested that. There was a difference by one order of magnitude, almost two

[@crazyman124ify]

I beg you guys make rting for air humidifier! Nice videos, love what are you doing guys, keep it up!

[@Adderkleet]

I don't need an air purifier, but I'm still really glad YT recommended this video to me. Love the methodology and style of these videos.

[@BrianHartman]

I have the Levoit 200S (not the Vital model; mine has no air purity meter). It's not terrible, but it's also for a pretty small space.

[@MrMoneyHelper]

Years ago rented a room in a house. I noticed that I was coughing more than usual. An expensive air purifier was not in the budget. A 20" box fan was purchased and some MERV 13 filters were ordered. I taped one filter to the back of the fan and within a day I wasn't coughing. Later I bought a carbon pre-filter to remove odors. It was a waste of money. I cooked a meal in the room and four hours later the odor was still there. The MERV 13 filter was changed every few months. That was done for years. The fan was given away when I moved. Years later I lived in a house with smokers. I should have just made another air purifier. Instead I bought a big Winix filter. It worked well but cost a lot.

[@gerceginpesindekos]

You add secondary contaminant "the motor". In ideal world, you should put motor before the filter not after it, especially if you use an AC motor.

[@silvahawk]

5:13 why don't you want the purifier to be dead center in the room?

[@MayaPosch]

For some reason box fans do not seem to be a thing in Europe, which makes many of us rather sad...

[@weslusk3798]

Check out Clean Air Kits, they use quiet and efficient computer fans.

[@Zaf9670]

There are people who make them using PC fans. They are quieter and if you combine 4+ some claim they will perform on par or close. You can probably find a 3D print shop that makes the brackets and then just need a basic fan breakout that accepts DC or USB power.

[@playlist5455]

PC Fans for radiators (like P12 or Silent Wings 3) are abundant and work better than a box fan.

[@GeneralKenobi69420]

Just get a Winix. 90€ filter included with shipping. Efficient, powerful, looks sleek too. Replace filter once a year with third party ones which are like 20€. Done.

[@alithabit8214]

Why there's no Xiaomi in the test ? Please consider it because in the middle East and Asia many of brand's in the video are missing

[@kkao33]

One aspect Ratings doesn't take into consideration is energy usage. Since those devices will be running almost around the clock. This is a factor to consider。 From what I can see the difference can be significant as some efficient air purifier only consume 20W to 40W. But other can easily consume up to 100W.

[@WildIppa]

So does the box have double the performance if its placed in the middle of the room?

[@lukasgayer5393]

Oh, how I wish the furnace filters and box fans were available here in Europe :D (they normally aren´t)

[@MainelyElectrons]

I found this out 6 years ago! If you add an inline activated charcoal can to the center and use a ducted fan the results are awesome!

[@Mark-h6k1w]

Could you please tell me where to purchase your particle counter and about what it would cost? Also what is the bottom panel material you are using (I couldn't understand what you called it in the video) and what is the brand name of the fan you are using?

[@HanmaHeiro]

Is this video unlisted on the channel? I knew I had seen the title and thumbnail but it took looking on the website to find it.

[@magicmanchloe]

Ok, how is there not a maker project based on the Corsi Rosenthal box that integrates some of those quality of life features, like a air quality sensor, Seven segment display and smart home integration with a low cost esp

[@tychay]

The AQ sensor probably should be separate/distant to the fan (My old Coway air purifier has one and it's incredibly unreliable). Plus a lot of AQ sensors measure VOCs in which they not the carbon filters are too small to do much to fix. As for smarthome, you have the right idea, but why put it in the device? I simply have a $4 zigbee power plug powering a CleanAirKit and have a HA integration that's better than whatever you can pay for allinone at any price: mine turns on/off based on outdoor AQ and peak/off peak/partial peak energy pricing, always turns on when the AC fan is running (since it sits near my HVAC intake), and always pauses whenever a door or window is open. Since the CleanAirKit uses PC fans, mine is incredibly quiet (louder than the Coway at its lowest setting but much quieter than the coway at the medium) and only draws 12W so fan speed control doesn't matter. You want the most air throughput anyway so if it's quiet enough to be a low hum and doesn't sound like a fan it's aces in my book.

[@temaus]

Using a 4” thick filter triples the surface area! Then you can either use a HEPA filters or just smack a fan directly onto that 4” filter.

[@dubsaru]

Very curious about the Blue Air filters.

[@feuby8480]

This is something. I really like your tests. I find the addition of DIY option really great here.

[@alexherrera3918]

Can you put a funance 4in filter on the walls? that will increase the filter area A LOT.

[@Derpalerpa]

Something I'd like to know is if it performs better blowing into the box pushing through the filters, or blowing out the top and sucking through the filters.

[@dlewis9760]

Supposedly by being on the floor and pointing up there's nothing or very little "Up" to hinder air flow. Blowing down, the CFM is going to hit the floor a couple of feet away and create vortices. Maybe even bounce back. That's the impression I've gotten by watching others explain it. Possibly if the fan was 4 - 5 off the ground it might be fine. I did see some that looked that high and had legs below the filters.

[@Ender_Wiggin]

You should consider testing the The 3D Handyman kits

[@annaburns5382]

I watched another podcast that built corsi rosenthal air cleaners, but they used 2 inch filters that worked better than the one inch. If I build one, I'll use the 2 inch.

[@ChetHanks-eh1md]

The problem with this box is that box fans themselves are unreliable. The lubricant wears out and the blades stop spinning. This wouldn't be a problem if fans were easy to dissemble , problem is they are not.

[@Calin8er]

How long do you expect them to last? In my apartment I use a merv 12 filter taped to a box fan to bring in air from outside. Another box fan to force air back out in another part of the room(no filter on that one). Both have been running for at least 5 years now. They don't run all the time just when the temperature and outside air quality is decent which it is outside of summer months. The fan with the filter had a plastic handle on it, it actually degraded and snapped off eventually. I replace the air filter once a month(it gsts to dark grey color). I have 5 HEPA air filters in my apartment as well 4 are whirlpool whispure(2 of which are over 10 years old), and I replace the filters on their suggestrd schedule.

[@artenman]

You need to follow instructions on the big and quiet and place it away from the wall with at least 1 meter distance between the device and any wall.

[@mindstalk]

The Levoit Vital 200S promises 1.27 CFM/$; the Levoit Core 300, without electronics, says 1.4 (140 CFM for US$ 99). (cfm = cubic feet per minute) (That's not considering the cost of replacement filters.)

[@francistower5352]

Love the Vid. Just in time for my decision to clean my bedroom air!

[@RTINGScomRD]

Thank you for watching and glad you enjoyed the video! Hopefully our video and reviews can help you buy what you need! 😄

[@EricLS]

As a former owner of a smoke machine, the instant I saw the spikes I knew it was the little drips that hit the vaporizer long after you’ve turned off the flow. I don’t know if it condenses in there and then eventually drips or what but it’s pretty odd how long it sits there before it suddenly shoots out a puff

[@ElectricEarth117]

Always wanted to do this but everyone thought i was crazy. Thank you

[@derekstewart5423]

Have you ever tested anything from the Aerus in terms of filtration, air purification and surface disinfection?

[@TheWebgecko]

Can you please test the kits by Clean Air Kits? Those have multiple smaller fans to be quieter

[@Ederick1936]

good lord, I had no idea that yall were from Montreal! no wonder you are reviewing Air purifiers :P

[@frosted1030]

Filter replacement frequency and price when discussing this, please.

[@twahly8170]

what is the absolute best for smells in an office enviroment?? Please tell me!

[@Spiker985Studios]

Agree with Beregorm88, however, I would also add that you can also get electronic timers so that you can accurately disable your smoke machine And if someone on your team is handy with electronics, you could also add an electric valve on some solid tubing to automatically cut off the smoke source at the same time - so you can get consistent results

[@fhirtzjr]

Am I counting five (5) air filters? Also, I cannot find any instructions on Wikipedia? Can someone help?

[@AlexSchendel]

I wonder if there's a version that could leverage a PC case fan for a much quieter and smaller build for apartments and the like. Maybe using one of those oval replacement filters for the Dyson purifiers... I've got a couple Noctua 5V PWM fans hooked up to a microcontroller for speed control. Modifying them to be air purifiers could be interesting 😁

[@thomaskelly393]

Wondering if it would be possible to ceiling mount the Corsi-Rosenthal. Would there be a reduction in performance if you could?

[@mensch4434]

i would really like to see someone test the gases etc. because noone really tests it so im unsure whether the filters are any good

[@XGD5layer]

According to the Wikipedia page with the instructions, researchers tried it and found out that this worked to some extent.

[@uss_04]

It might work well but I really appreciate cleanable prefilters. Still might be good in a pinch

[@bluetonight17]

since the box fan set up is so good, can we see it with more than 2 secdonds of smoke? like 10 seconds to really pump that room nd see how much of a differance it really makes?

[@HouseFresh]

That’s a massive cr box , what hvac size filters are you using?

[@mikaelhakali4980]

Please review the Vitesy lineup of air purifiers. They have some interesting plant-integrated versions and other sorts of portable purifiers. Their selling point is washable filters without performance impact saving on running cost.

[@RTINGScomRD]

👀

[@MatHanley]

Wait, are those carbon filters actually pointless? I've been getting them on the cheap IKEA purifier because I have medical cann' flower and it smells and I use both filters and it does make a big difference and the smell and vapour does shift very quickly. I'm now very conflicted, but that's not a bad thing.

[@Weaver_Games]

It depends. Some are better than others. I bought some Blue Air "Smoke Stop" carbon filters and, IMO, they did absolutely nothing. I also have the Dyson Big+Quiet that I found did actually work against formaldehyde, but still doesn't have enough carbon to really do much for VOCs. That said there's units designed for high VOC environments from AllerAir (it's VERY expensive) but these things run 24lbs of carbon and are absolutely capable of absorbing smells and VOCs from the air.

[@MatHanley]

@@Weaver_Games Because that's all the kitchen extractor fans do that don't exhaust, they have carbon filters to remove smells. Are they esp different?

[@gg-gn3re]

No. Carbon filters remove stuff these don't, such as odors. The merv 13 are better for the pollen etc though. usually higher end filters will use both layered on each other.

[@Jaker788]

Yes. There's not very much carbon in any of the filters to do anything significant for very long. You'd need a little more carbon than a thin layer over the filter or pre filter..

[@honeybee4889]

Would your team consider testing different streaming devices? Additionally comparing it to streaming directly from smart TV’s. I can’t seem to find an extremely clarifying answer to the questions I seek. What is going to provide the best image and audio quality for my TV. I’ve heard most either recommend Apple TV 4K or Nvidia Shield. I just purchased a S90D tv and would also be curious if these streaming devices provide an upgrade in quality to high end smart TV’s. Lastly if a TV does not support something like Donny Vision but I were to stream from an Apple 4K tv which does support such a feature would the streaming devices support translate to the screen? I know it’s a lot of questions but if anyone were to know/care about the answer it would be RTINGS! Been loving your KZbin channel and checking out your website also as a result!

[@RTINGScomRD]

Definitely could be something we do in the future, we just can't make any guarantees at this time. Sorry about that!

[@Hfil66]

The problem with most of these reviews is they only look at cost and performance at time of purchase. What would be more interesting is how easy is it, and and what cost, to replace filters. What is the cost after two or three years of use (how long do the filters last and how much do they cost)? If one box is twice as good as another, can this be mitigated by using two boxes of the less effective variety - what is the cost and space usage penalty of doing so? Filters aside, some air purifiers also use electrostatic plates and UV light - what is the relative impact of these (they should not cost as much in terms of loss of airflow as a thick carbon or HEPA filter)?

[@jtland4842]

Is it possible to do some sort of noise normal-sized results? Another way to make the a DIY air purifier that is quieter is to use PC fans. It will definitely be more expensive and more complicated but it should be much less noisy even at the same noise level it should perform better especially if you choose high quality fans at the correct size.

[@ZenAndPsychedelicHealingCenter]

PC fans are tiny and wouldn't move enough air. This is not to cool small parts, it's to clean the air in a larger area.

[@csimet]

More surface area and greater airflow, simple physics. I have one like this in my workshop built into the ceiling for shop dust, but I'll stick with a nice looking commercial unit for my living space.

[@leoceoliveira]

Very cool! I wonder how they perform with PC fans!

[@ococoseco]

The site doesn’t allow for air purifier product review suggestion yet. I’d like to suggest the TruSens Z-3000

[@RTINGScomRD]

We will open that up once we're closer to a time where we'll be buying more air purifiers (30 days before most likely) :) Thanks for sharing!

[@notnewtohere]

why did you mention levoit when your article shows better performance from the honeywell HPA300?

[@XGD5layer]

Likely because it outperformed it towards the end. The 600S ended up with the lowest 0.3um concentration of them all towards the end of the test, despite losing initially due to worse airflow.

[@notnewtohere]

​@@XGD5layerI don't believe this is true. Hpa300 device is rated well for what it is. It's biggest full is that it has none of the sensors of a modern device, it's basically filters and a fan. But I honestly want to know the reason considering this video is all about a self made device that's only filters and a fan.

[@XGD5layer]

@@notnewtohere I said that because their article with the measurements seems to suggest it

[@notnewtohere]

I double checked their website and rewatched the entire video. It does not suggest the HPA 300 lacks performance. Their own review of the HPA 300 complaint is that it's loud and uses a lot of power and calls it a store bought cosi Rosenthal box. It's ability to clear rooms of particles was slightly better than the levoit on their graphs on the website.

[@XGD5layer]

@@notnewtohere looks like the levolt they mention is actually not even in this review. For that review you have to manually navigate to it. Its effect was marginally worse than the hpa but the end result was a lower particles per litre, so it ends up better. It's similar to the 400S in this review

[@oni7729]

You guys are awesome, please do refrigerator next

[@TimJohnson-x1o]

If you want a real solution, get an industrial air scrubber. You can get generic ones for as little as $250 and they are VASTLY more effective than any of the consumer grade stuff or these homebrew kits. These systems use durable and very powerful fans. They use 3 layers of filter, first is a furnace filter. Usually merv8 but you can use better ones if you want. Second layer is usually 1" carbon. But again you could use something else, like say 2x 1" merv 13s. The final layer is a 2"-3" true hepa. Some of them also have UV lights inside to keep sanitized. Another thing to consider is the cost of replacement filters. Thats where consumer systems get you. Most systems cost nearly as much for a new filter set as they do to buy outright, including filters. It's clearly very intentional and how they make their money. Good thing about industrial scrubber is no games like this.

[@jan-pcro]

i saw the shelf with blenders there and i am very interestes!

[@user_5670x]

What about Rabbitair a3. It's recommended by Forbes as the Best overall Air Purifier.

[@ameliabuns4058]

Does this also help with allergens? also I'd love to see info on how accurate the built-in sensors are. most from what I know are useless!

[@SnakebitSTI]

Yes, but an air filter is not a complete solution. It can only remove allergens after they've gotten into the air, where you can breathe them. Removing sources of allergens is still important. Minimizing soft surfaces (furniture, carpets) which can trap allergens helps, as does frequent cleaning (e.g. HEPA filter equipped vacuum).

[@ameliabuns4058]

@@SnakebitSTI it's still helpful afaik. It helps filter the leftover allergens.

[@redStiv]

You could cover the box in speaker cloth to make it look a bit nicer.

[@ZenAndPsychedelicHealingCenter]

Which totally negates the point of the filters in the first place.

[@redStiv]

@@ZenAndPsychedelicHealingCenter how?

[@dlewis9760]

@@redStiv It's a filter.