What is the best DIY Air Filter?

RELEVANT

I only have 3 filters for my box fan, but for filtering the small amount of highwah dust that makes its way into my apartment, this should be good enough until I get more! I'll make the cube design, with 3 sides and go for it.

So how do they compare sound-wise?

As you stated, the CFM specified by the manufacturer rarely reflect real world experience. One thought I have had is to use electric fans from semi-trucks. Thia would require a 12V DC power supply that can be found at no great cost on Amazon or from companies such as Digi-key. Just make sure the current rating of the power supply meets or exceeds the current draw of the fan. If you can locate a semi-junk yard within reasonable distance the cost of the fan should be minimal.

You would also be on your own when it comes to the protective grid in front of the fan. An oven rack from a discarded stove may work depending on your build configuration. Those fans have to move a lot of air to keep those big diesel engines cool, especially in hot weather and under a maximum load. Testing one on the wind tunnel would be interesting.

very interesting, saw some videos as well of turning a pc into a filter too. thanks for the vid

The benefit of the shroud is probably because it allows the fan to be partly centrifugal, blocking escape of the air flung to the sides. For cases like this one where some pressure is needed, centrifugal fans perform better than axial fans.

I love what you are doing here, and I don’t know what to call it. Is it science? Would you call yourself a scientist?

This mid-size air purifier is excellent.With the wildfires spreading into the NY air, this little machine gives me peace of mind.Chic design, user-friendly and a must-have!

I bought my Lasko and 1” 3m Merv 10 from Walmart for $26. That brings the cost down to $.15 per CFM. A little cost-fudging going on.

So here's a question for thought. If the air king fan is ($50 +/-) and a high velocity fan a cheap on found everywhere is $50.. how much better of a performance do you get then using these same filters..

Hola!🖐By far the best video I have watched on the topic. This is also my very first video of yours I have come across. I'll be watching more and more of then now. Thanks for all your work and effort then sharing your findings with us all. Take care and have a good one, Adios!👊

Looks Like you Put a Lot Of effort into this project. I appreciate this. Alvin

what's the cadr level?

First, this series is incredibly helpful, so thanks very much for putting it together. Second, I'm trying to decide between your "standing" design and one of the ceiling mounted ones. The ceiling are nice because I preserve valuable floor space, but I'm worried that the increased distance from dust source means it won't work nearly as well. Any insight into whether that's a notable concern?

funny carpenter sent me over. Subbed! Great video.

My brother is a mechanical engineer specializing in HVAC... He would need impressed with your thoroughness.

Interesting. Considered testing with a blower door & manometer?

I am shocked...
I cannot believe you really fucking measured CFM FREEHANDED???!!!!!
YOU ARE SUPPOSED TO FOCUS THE WHOLE FAN INTO THE METER....
Think an Air FUNNEL focusing ALL the air into the meter, not a fucking air tunnel and then measure 2" spots all around...
For fucks sake bro...

Hi! Thank you for your awesome videos on DIY air filters! They are very much appreciated! In this video I´m missing a conclusion of which filter thickness would be best? is it 1", 2", 4"? And what would have the best cost-benefit ratio? I remember you saying that 4" filters are best in terms of airflow, but in your newest videos I don´t hear them mentioned?

Wow! Very impressive video! Really well done 👍👍

Such a weird, CGP Grey way of speaking.

Hi Sorry, I can't tell if this is valid: would using the lasko or king fan work with either of your two fan designs ? or us their ability to pull air still too low and wouldnt become more effective with the stacked filter tower shape of your two designs?

Hey one thing I was wondering today, do you think the Maxx fan + 8 filter build is strong enough to lift settled dust off the ground and filter it through the fan? Or am I thinking about it wrong and it's still gonna be only strong enough to filter dust that's airborne?

Relevant comment

You get what you pay for.

Good Job, Beneficial truthful information. Crossflow seems to be key in a work area. All so ducting from the proximity of the source of the material to be removed from the air. I have used restaurant grease hood fans, they have large cfm and used ones can be found very cheap, with the bonus of being explosion-proof.

Great vid

Those mushroom decor pieces are sooooo pretty. Do you make & sell them and if so, where do you sell them?

After watching and rewatching a number of videos lately about diy air cleaners, a couple of things caught my attention, issues and ideas perhaps worth mentioning:
At some point in the comments - this video, I think - you responded to a viewer that you were interested in the idea of using two fans in a push-pull arrangement. I’ve kind of wondered about that too.
At some point in the video or comments, you remarked that the drum fan atop the box of furnace filters could be set to pull air in through the filters and out through the fan, OR the opposite. Furnace filters generally are designed for air flow in one direction. You probably know that. That also applies to canister filters. They are designed to pull air in, leaving dust on the exterior, or to push air out, catching dust on the interior, as in the case of dust collectors. I have no idea what would happen if filters - furnace or canister - were used in the incorrect orientation, but manufacturers suggest failure, I suspect damage to the pleats and to the structure, creating leaks. Perhaps you are aware of these issues; some folks will not be.
Q1: instead of placing the drum fan atop a box of furnace filters, what about placing it atop a canister filter?
Q2: would there be a performance difference or advantage/disadvantage to a pull arrangement vs a push arrangement? In the case of a Corsi Rosenthal air cleaner, the consensus seems to be that a pull arrangement is better. However, I don’t believe I have seen any particular tests, data or summary explanations anywhere - ie, no reasons.
Q3: Inexpensive commercial air cleaners appear to employ small axial fans. Better commercial air cleaners employ relatively small centrifugal blowers, aka squirrel cage blowers. Dust collectors employ fairly large impellers. My understanding is that a furnace blower is far superior to an axial fan, for an air cleaner. What about the impeller? Is there some reason NOT to use an impeller for an air cleaner?
Q4: This is actually an idea, and a variation on it, something that might be worth testing - or perhaps there are good solid reasons against. Here goes: a Corsi Rosenthal air cleaner on the front end, to act as a pre-filter, a canister filter on the back end, and a fan in the middle. Variation 1: dust separator on the front end. Variation 2: a second fan up front.
I’m still learning the ropes of woodworking, finishing, dust management, etc., so please bear with me.
I would really appreciate your thoughts. And please, I make mistakes all the time. I am not averse to the truth. I’m retired, well over 70, and tell my students that someday I may figure out what I want to do when I grow up. For now, it’s this - learning, trying things, repairing old tools, making mistakes, learn some more.
Stay well.

In both the audio track and slides, the Maxx Air 17” fan was mentioned. I have been unable to locate any information about a 17” Maxx Air. I was able to find links to a 10” and a 16” Maxx Air.

you think four 2" carbon filters would be better than four 1" carbon filters on the box design? also, Nordic pure sells a "pure carbon" filter with more Carbon (Merv 8) ........ will that restrict air flow? i want to use this for smells mainly?

Hey im thinking of using your 8 filter design with h13 Heppa filters that have charcoal pellets?

1) Can i make it quieter?

2) Any DIY methods to add a pre filter for hair?

3) I noticed you mentioned youre releasing another round of tests , 0.0 when 🎉

Decided to look at this video again. Great work, really impressive!

Nice video, with actual results. Gives me a lot of food for thought. Also, nice Ted Drews shirt! love me some frozen custard.

Finding your video after I bought the Lasko and the return window closed. That checks out.

Not sure if somebody said this already, but you can check if the shroud is blocking all the air from coming in by sliding a piece of paper or tissue from the edges. Shroud shown in the video might be covering up more than necessary reducing the flow a bit. Although I'm not sure if it'll affect it much and it's more work with trial and error, but you can see more precisely at which point the vortices are blocked and not blocked more than necessary.

Have you tried any kind of setup that you utilizes an air mover instead of a normal box fan? I'm thinking essentially make a cube out of air filters but cut off small hole for the air mover outlet to pop out but sure if that was something that's been tried.😊

Nice work

Those diagrams at the end made me think . . . .
Have you considered a whole house fan? Those things move massive air and are not TOO expensive..

Thanks for your hard work on this. Very impressive for a programmer!

great video! new sub here!!!

Thanks!

Way to late for the contest,oh well

​I bet a lot of woodworkers would love to see you dive into alternatives to the expensive canister filters for their dust collection systems. Me, for example.

I've got a dust collector with a 700 CFM fan. It's got a cyclone separator in front that catches the big particles, but I want to replace the collector's cloth filter bag on the output side with a filter box using one of your designs. The fan's output comes through a 6 inch duct though, so the stream is really fast and really concentrated. What sort of diffuser or plenum can I build to put ahead of the filter box?

when a fan is rated to move X CFM, it includes the air brought along with the air coming out of the fan directly. You can't just make a wind tunnel for it and expect the same amount of air movement. Bernoulli’s principle!

Hi, sorry if you mentioned this in the video and I missed it, but do you think that this would be a good system to have near a spray booth?

This was very helpful. Thank you.

Great video! Curious what you think is a good rule of thumb for how often you should change filters?

Assume AirKing with 4 Merv-14 20x20x1 filters in a weekend warrior woodworking shop