Air Filter Updates & The Science of Air Filtration 

Damn, guy. Selling the discounted 3D-printed parts and providing free plans is really kind of you. Thank you.

I built the 8 filter version with the 2500 cfm fan for our non-profit Made4Me shop and it has made a significant difference to the air quality. We build adaptive furniture for handicapped kids using cardboard, which leaves very fine dust in the air when cut. Thanks for your work here!

Lol I didn’t realize I was a nerd until it just hit me that I’m watching these videos while doing dishes and ONLY listening to the audio. You’re doing an incredible service for DIY peeps at home. Thank you so much man. ❤

Dude! How am I just discovering you! You are a real builder, well spoken, and your graphics make it soooo much easier to understand how it goes together. Thanks!!!

Impressive dedication on your testing rigs. Thank you, truly. That's a public service I know took you some time, effort, and money.

Great stuff! This series of yourinspired me to rebuild my single-filter, box fan version. I love everything about what you've done here: good methodology converts specs into the real world. Thank you.

This is a great DIY build! I built and have been using mine with the original orange fan for quite awhile now and can attest to its function. With some mods to the original plan, it is now even better. With an added filter on top of the fan to keep dust out of the motor, and a longer power cord/external switch, this unit keeps my small garage shop free of airborne dust. I have ordered the Cat black fan to upgrade the power of my unit. No more hacking cough after a day making sawdust. Thanks again 3D Handyman for putting this plan out for all to use.

It's crazy how people come up with the same ideas all the time, I've done this on my intake for my old greenhouse i built in the basement. 2 box fans listed at 2200 CFM and 3 filters plus 2 more fans for the exhaust with another 4 inch filter to catch pollen. Works great, i should've gotten these bigger fans though cause these things kick ass

Great job and very nice of you showing the plan how to make it - keep up a good work

Can’t wait for the rest of this series!

Can't wait for the next addition to this series and seing the other versions in use

This is awesome! Thank you for making this video. Definitely going to build a few of these for my woodshop.

I don't know how the algo got me here, but i'm glad it did. I have massive attic work that needs doing, and it's beyond disgustingly dusty up there, especially after just having my roof replaced. I started using a lasko fan with a cheap 1" filter, letting it get sucked on the inlet side. it helps, but I can see building something better and letting it feed for a couple hours while periodically hitting everything with a battery powered leaf blower, is going to make my life MUCH less of a living hell. So thanks for that, and for convincing me to spend money. :D

A box fan has a fractional HP motor. Generally around 1/25 hp to 1/32hp. It's merely designed to move air, not draw it through static pressure. A furnace blower on a 3 ton air handling unit employs a centrifugal fan with a 3/4hp motor. And it's rated to between 900-1300 cfm. I can provide the tables from the manufacturer upon your request. Design of blades, and housing matters here. A fan meant to just push air with 0 static pressure and 0 resistance can use propeller blades. Exhaust fans get away with them because often the air they are moving is hot (think kitchens) and hot air naturally rises. So the fan is actually just directing it out a vent. Same principles with a chimney on a wood stove. You get good draw when the fire generates enough heat to start pushing up through the chimney. Until that point the fire can actually smother. Air becomes denser (and heavier) when cold. Humidity also affects characteristics of air. All these things will change your fan's performance. Try placing the Corsi Rosenthal Box filters in the tunnel and have the fan pointed into open air. Place your anemometer anywhere in the tunnel and check wind speed velocity. In all air filtration systems emphasis should be on draw rate. Nobody cares about exhaust rate because that's filtered air. Measure draw rate. Impelling dust into your box (pusher configuration) your anemometer will have a high velocity because it has 0 resistance. On the other hand your math equation won't have the huge surface area, but that's how the math has to be done. The design of the CR Box pulls air through filters, and thus resistance to flow becomes a factor. So you measure air flow drawn through the filters. I have personally put a lit tea candle inside my CR Box. The air flow through the filters did not snuff the candle out. Made me scratch my head and realize the purported math was wrong. If you put a tea candle next to your AC's return duct it will snuff the candle out. A centrifugal fan is specifically designed to work when resistance and pressures exist. It also is designed to create a low pressure environment inside the return ducts. Further inducing house air to enter and go to your furnace, and A-coil. www.ccohs.ca/oshanswers/prevention/ventilation/fans.html GREAT JOB! I love your curiosity and willingness to investigate. You've the mind of a real scientist and critical thinker.

Top notch information! Thanks

I built box fan filters using 4 inch filters instead of 1, and they seem to do the job well enough, best budget option. You can even use more filters if you want more airflow.

AMAZING VIDEO LOVE THE NEW VIDEOS

Spent 3 years I. A commercial cabinetry and furniture shop and dust collection physics and mathematical formulas can become wildly complicated quick. Nice video and use a push stick always

Awesome to see you doubling down on the content that worked for you! Just getting started with taking RU-vid seriously and the 3D printed kits/parts for my projects was an avenue I was considering. It would be cool to hear about how well this works out for you on a monetary level and how you balance the workload of making videos and these parts/kits. Thanks for sharing!

Can't wait for the next part.

Absolutely Amazing~!!

I'm eagerly following this filter series! Im interested for the potential of low cost DIY air purifiers for general home use. Ive not had luck finding a fan thats ideally affordable, powerful, quiet, and energy efficient. The centrifugal fan in the Coway Airmega 400s purifier is pretty good, whatever that one is. Rated at 410CFM of HEPA processed air drawing 69 watts. The downside is the ~$400 price tag and high replacement filter cost times having one in each room. Your videos are giving me good info.

You are correct when mentioning the long tunnel for allowing air to stabilize before reaching the fan. It's called laminar flow Vs. turbulent flow. TLDR laminar flow it's like a quiet in-line fast flow stream of water (air is a fluid), and turbulent flow is chaotic, noisy and non efficient. I've built my own filter for my workshop and have done some research beforehand, and from what I can remember the minimum distance between the filter and the fan should be 10Cm (4" in _Freedom Units_ ). Nice video and keep those fingers away from that saw blade, *yikes* !!!

Really, really awesome! 👍 Thanks for investing the time to gather all this data and information then sharing it with us. I'm "blowing"💨on over to your next video! 😂Take care and have a good one, Adios!👊

You should also try to measure the difference in pm2.5 coming in and coming out of the system, especially over time.

Axial fans are optimized for volume. Radial fans are designed for pressure (or resistance). Mixed flow fans hit the sweet spot in between which is ideal for your filtration needs. You can see this in your CFM drops with filtration added. You're wasting over 50% of the air you're shifting with your DIY solution. The ideal fans for you IMHO would be the Soler Palau td silent series which work well even with a little resistance. You don't want to be blowing dust off the floor and making so much noise that you cause more trouble than you're out to solve! It's also nice to pre-filter air hitting the fan for longevity!!

Sweet video, any chance in doing another indepth review on a welding fume hood that is mobile and stuff... Thanks!! Cheers!!

Great job covering the key points. If I have a two story 4000 square-foot home, which model would best be able to accomplish the job and where would best be placed in the house?

Awesome, Thank you. I have a project coming up where I will be cutting a quantity of stone in my apartment workshop. Obviously I am going to need a high quality air filtration system before I even think of cutting anything. My intention is to draw 100% of the dust into a filter/fan and then blow the exhaust air out of a window. I am thinking something like a fume box used in chemistry labs. That way I have both a physical separation from the rest of the shop and the directed air flow for the dust. Both removing the dust from the air and not having a stream of dust coming out of my window are my two main considerations. After watching numerous homemade dust collection videos on youtube I find that the information that you are providing to be hands down the best that I have seen so far. Plus you offer free plans! Excellent, and again thank you for providing a superior level of information for us DIYers. It is very appreciated. I don't normally subscribe to channels, (I think that you will be the fourth that I have added since the beginnings of the internet), but for me, yours is a no brainer. Looking forward to seeing what else you have produced.

Thanks!

Thank you for objectively testing things. If I could block every channel which gives opinions without tests, I would. Instant subscribe from me. What brought me here is my interest in filters for VOCs with activated carbon--thinking of options for a cage for filter media which is cheap in bulk, but expensive in genuine replacement filters.

This is amazing an thorough. Would these reduce pet odors?

Extremely well researched and very well done, thank you for this! I would love to build the downdraft version - I think it would work well for flying dust from mitre and table saws. Do you have plans available for that version? Thank you.

I have to say, this video, and more to come, are very interesting. I suspect one advantage of the "cylinder" fan relative to the box fan is that the latter has corners through which airflow can return around to the intake side. Also, when you connect a fan to a duct, that duct creates some resistance to airflow, so the resulting flow rate will be less than for the unducted fan, possibly explaining your noted discrpancies? Indeed, if your tests include a measurement of the pressure generated by the fan (or vacuum for sucking), that would result in much more meaningful comparisons between fans, and between filter arrangements. Hmmm, I can't help feeling this is probably already a topic of study by home-filter-builder enthusiasts :-).

I've ordered parts to build an air purifier. An uzman ksa-400 fan (200W), and a 405x405mm filter stack consisting of a prefilter, activated carbon filter and hepa (filters 0.3um at 99.97%) filter. The entire stack is 125mm (about 5"). It's for those times that the air quality is bad or pollen is a problem. Mostly fire wood smoke, diesel exhaust fumes (rural area with lots of tracktors and trucks), ferillizer etc. Especially around easter, my neighboring country Germany light fires (garden wood etc) nation wide which often blows over my living area. I have a hard time breathing during those times and avoid going outside. It can last up to 3-4 days depending on wind direction. Hopefully this will help getting some clean air inside despite the outside conditions. I can also use it when I'm soldering electronics, woodworking (cnc, sanding etc). I've ordered enough materials to build 2 of them and/or experiment with differen configurations.

Ah very nice / okay I appreciate the great videos !

USEFUL, INFORMATIVE, PRACTICAL, AND FISCALLY CONSCIOUS. This hits all those important boxes. +Subscribe

fan direction is intriguing. I wonder why most all suck air through filter if the system works better blowing duct through filter?

Thank you for the video. Is there a difference between the direction the fan is facing (before the filter vs after the filter)?

@The 3D Handyman - Video Suggestion: Could you test the Sanders flexible and cuttable 0.1 submicron containment filters pads with low static pressure , gasketed in a frame design, in your DIY HSA box fan.

Concerning blowing into versus out of the filters. Sucking air tends to cause a short circuit, while blowing creates stream of air away from the unit thereby circulating air in the room better.

It is worth pointing out that you get a lot more filter area for your dollar just by using 16"x25" filters rather than 16"x20". The difference (today) on a 12-pack is $5! 20"x25" 12-packs are an even better deal. You significantly increase your available filter area with almost no increase in price.

What do you think about adding it on top of the harbor freight dust collector? The Wynn filter is very expensive for a small hobby shop.

Do you have a build list for this? Also, any reason you ahem the fan blowing in rather than pulling through the filters?

Question: Do you have any data comparing the standard 1" thick filters with the 4 or 5" filters on the market? Impatiently waiting for the rest of the series! Really interested on what went into "Beastie Boy"!

I really enjoyed your video. Question, on one part of your video you show dust flowing into the filter. then you show on another part of the video dust flowing into the fan first. Also, if you are spraying in a homemade paint booth, wouldn't the filter protect you from possible fire?

Thank you I am building one of your designs.

Where is the "Lies in the wind" video discussed at 46 seconds? My AC ceiling return pulls most of its air through the center of the filter, which wastes most filter material. I am wondering if a plenum (box) above the grill and filter would better distribute the intake air over the entire filter.

Hello Sir, I don't have a shop to build one of these units. I'm wondering if you will build the frame and ship the necessary parts (excluding the fan) that I may assemble and use in the space I need it in? Thank you, John

I was wondering about MERV ratings, and whether they are the total percentage they can remove over time, or for a single pass. It sounds like it’s the latter, but I struggled to find any good information on this. Do you have a source that talks about this specifically? Thanks so much for making these videos. Really an incredible resource.

Is that true about the amazon link? I got about a thousand dollars worth of crap ready to order for my shop in my cart! I got you, bro!

Thinking about building the ceiling mounted versions and hanging them from my 92" garage ceilings (kinda low). Just looked at the plan and it looks like the fans are pointed up (towards the ceiling). Wouldn't it make more sense that they're facing downwards, where there's a greater volume of air to pull in?

Although you like pull mode, is there an advantage of pull vs push.

This is great content, thanks for your work on it. I wonder if you've considered or tested cartridge cylinders matched with the Caterpillar fan? The Wynn 35B222NANO Cartridge Kit filter is more expensive but smaller, MERV 15, and 222 sq. ft of filter surface area means tons of capacity by my math. Very simple "assembly"... I saw this on the MMCC_Woodshop channel.

is there a version of your DIY rosenthal boxes that I can mount to the garage ceiling? floor space is limited... Also, I only use tools / create dust when the garage door is open -- is it still worth it to run a box like this during the cuts? Does it help to run it overnight when the door is closed, or is that too late because by then the dust has settled from the air? Thanks

Im trying to decide if I should use furnace filters vs some like a Wynn filter. Any thoughts on why you chose furnace filters?

Hi there - thanks for the great videos on air filtration! I am thinking of building your design for the "Compact - 1700CFM Ceiling Mounted". Is the intention of this for the fan to be blowing inward (up) or outward (down)? Thanks again!

Great videos. Do you know when your next one in the series will be published? What type of fan are you using in the "compact" and "beastie boy" units you preview? Do you have plans for them you would be willing to share?

do you have plans for the beastie boy? what's the difference with that one vs. the tall one? I'm gong to build one. just got a CNC and even with vac it's dusty.

Do you have a filter box build guide?

Have you tested dust performance with an air quality tester between push / pull configs? I've read a few articles that having the air purifier blowing air straight up and sucking from the bottom provides an increase in performance. Since CFM isn't a qualifier of how much is being filtered.

have you looked at the Wynn filters. they are merv 15, and cleanable. at a good price.

With the fan blowing down into the filter chamber, doesn’t it kick up the dust it had already previously trapped?

Not a bad impersonation of CGP Grey's performative RU-vid voice.

Incredibly helpful content! I've heard a debate on TikTok and other sources online that suggest pointing the fan inwards, such that the air flow goes through the fan and into the box to filter versus what you have testing air flow out of the box, sucking air onto the exterior of the box filter. Mind commenting on that topic? Hope that makes sense.

Looks like there is a fabric wrapping over the filters. Is there? And if so, what is it? I don't see it in the parts. I am asking because I am going to construct your design myself.

I bought the same Caterpillar air blower 4000 CFM. Which speed do you normally have it on? The highest (4)? Thanks again!

I was wondering if an air filter like the one you made is good for just oulling natural dust out of the air in our shop. Is it something you need to run all of the time or just occasionally?

Is there a reason you didn't add another filter at the bottom would it reduce the air flow? or increase?

how long do the filters last with normal use?

Did you design any other layouts for this yet? Like a ceiling mounted one?

The only thing preventing me from wanting to do this is the ability to hang from the ceiling and have a remote+timer. Space is at a premium in my garage and while I could hang it, the cost of hardware and a timer box puts the build near the price of the Wen at $134 rn. Fully aware this 4 filter system filters more but not sure if I absolutely need it.

What would happen if your caterpillar configuration included another fan at the other end of the filter box? A push/pull configuration.

How big is the smallest sawdust particle?

What screen material did you use on the outside of the original build? Great video!!!

Hey bud have u ever tried reusable filters like the electrostatic furnace filters would that work ?

Can you run the filters in series so a lower HEPA filter picks up the bigger particles, and is backed up by a higher HEPA filter. That would decrease the need to change the more costly higher rated filters? You may have already addressed this, but I could not find it.

begs also the question of electro static filters.. the metal ones that should last like 10 years any thoughts about that one

How many CFM is the orange fan? I have same one from home depot ans when I checked online is showing only 1600 CFM.

Isn't the push confirmation a pain to clean the inside of box? Or am I missing something.?

Do you think this has more CFM than the Donaldson P181038 Filter?

I followed a RU-vid dust-collector design that didn't require building a support structure. It uses the same Caterpillar fan which simply sits directly on top of a canister filter. I've performed some tests on this system and the results are underwhelming. Your system has a much larger distance between the fan and the end of the structure. Do you think that the added distance between the fan and the structure helps?

Do you think the fan matters that much? ie could I use my 30in harbor freight fan (6500 to 9540 CFM) in a modified beastie boy?

Not sure if it is too late to ask but what is the depth of that fan? Trying to figure out if I build this exact system if it will fit where I want to store it. Thank you!

Did you end up building a filter for the fan motor itself?

I'm getting my materials ready to build this. I looked through comments but haven't seen anything: what's the mesh screen you have around the outside of the unit? Or is it just my imagination haha.

Do the pc fan CR box filters really push the same CFM at a fraction of the energy consumption of a box fan CR filter? Some clean air kits claim 7-10 watts!! That would make it over 10x more efficient than the air king box fan on its lowest setting!! 😮 Definitely something I want to consider, since it’s much quieter at almost the same claimed given CFM, if that were true.

how is filters make a paint work area?

Where can I find the drawing? Thanks!

I picked up some laskos average price 20$ im wanting to order your kit C but got to thinking about a hack. What about adding feet and flipping on its side and put 2 laskos on opposite ends blowing outwards. ?

I'm a little curious why you wouldn't flip the fan over to pull air through all the filters rather than blowing into the filters? Just seems like you'd get more air filtered by sucking air from the whole box.

Hello! Why is the fan not installed backwards, because then it would not be clogged with dust?

i think to better capture the true air speed from a fan, the tunnel should be at least 1 ft wider than the fan to eliminate as much boundary layer as possible so that the centre of the tunnel is closer to the real world air speed without boundary.

Hi there. How long till you have to change the 8 air filters? You think I could vacuum them and reuse them? Thanks!

What kind of mask at around the 4:30 mark?

Lies in the wind.... Partly cloudy with a chance of drama!

Looking to build your 4000 cfm fan. Have you measured the decibles of the fan at 4000 cfm (real world)?

Blowing into filters and similar loads like heat exchangers is not recommended, it's always preferred from a fan performance standpoint to draw through. The airflow from the fan outlet is turbulent and very directional so you'll get poor distribution, load the filter unevenly and get unpredictable airflow when you compare with the stated fan curve. The comment about fans being tested with ducts in the way you think of it is not always true. If you look at a datasheet for an industrial fan it will have a fan curve which tells you the flow vs static pressure in a standard test configuration, thatc configuration can be any combination of ducted or open inlet or outlet. The fan curve should have small diagram with it that tells you how the fan has been tested. Most of the time the way the fan is tested will correspond to its intended use. A fan designed to be used in a ventilation duct will be tested ducted inlet and outlet, a computer cooling fan will be tested open inlet and open outlet.

They don’t seem to sell that fan anymore. The maxx air.

What fan is the Beastie Boy design using?