BOX FAN AIR FILTER For About $40! (How To Build a DIY Box Fan Air Purifier With HVAC Filters!)

BOX FAN AIR FILTER For About $40! (How To Build a DIY Box Fan Air Purifier With HVAC Filters!)

Hurricane 20″ Box Fan (Amazon Best Seller):
Filtrete 16X20 AC Air Filter 6 pk. (Amazon Best Seller):
Filtrete 20X20 AC Air Filter 6 pk. (Amazon Best Seller):
Lasko Air Flex–Built-In Filter Box Fan:
BlueDri HEPA Air Scrubber:

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BOX FAN AIR FILTER For About $40! (How To Build a DIY Box Fan Air Purifier With HVAC Filters!)

Fine sawdust floats around in every workshop, potentially causing lung-related health problems. Most dust collectors and shop vacs fail to collect it all. This short video from The Honest Carpenter will show you a great way to turn an average box fan into a homemade air filter/purifier!

Large, single-stage dust collectors are great for picking up wood chips and sawdust–but they’re actually prone to pumping fine dust back out into the air.

Also, they’re not great for tools smaller than shop planers, joiners and cabinet saws.

Shop vacs, on the other hand, work really well with those tools, because they draw a lower volume of material at a much higher pressure.

However, it can be hard to bring the suction close to the source of the dust–the blade or cutter head. Therefore, a lot of dust both coarse and fine gets blasted out into the room.

This dust can cause lung problems both immediate and chronic!

The best, most affordable way to trap this fine dust is with a homemade box fan air purifier/filter.

You can make these units with just an average 20″X20″ box fan, and a couple home HVAC air filters.

I used two 16X20 filters for my box fan air filter. I just built a 1/2″ plywood frame with cradles and slides for the filters, and lower lip at the front for the box fan to sit on.

Then, I duct-taped the air filters to the plywood frame to create better draw and suction.

In just twenty minutes, a box fan air filter/purifier can complete multiple full cycles of a small workshop, drastically cutting down on the airborne particulates!

Thanks for watching!

The Honest Carpenter


  1. KrisRaps on June 8, 2023 at 12:36 pm

    Watch This Video, Maybe This Would HELP Your Situation Much better.

  2. Tee U. on June 8, 2023 at 12:36 pm

    I’ve seen different designs and am not too sure of the pro’s and con’s in regards to fan direction.
    Wouldn’t it be better to flip the fan so that the dust inlet becomes the fan side and not the filter side? Won’t this increase inlet strength?
    If anyone knows the pro’s and con’s of this idea, please let me know.

  3. Curtis B on June 8, 2023 at 12:36 pm

    I just use the filter directly on the fan in any spaces I’m working. It isn’t going to filter the room but it will help reduce the crap it is blowing around.
    I also use that exact fan and a 20" filter on our upstairs window as we use it in the summers in the evening to help force the cool air in but don’t want to force in all the outside dirt and pollen.

  4. David Suarez on June 8, 2023 at 12:37 pm

    Great video. I just came across a 500cfm air scrubber exactly like the one you mentioned at the end of the video. Can i use that for regular woodworking?

  5. Pbcarney on June 8, 2023 at 12:39 pm

    you can buy a roll of filter mesh and tape it on for a few bucks works great.

  6. Hen Loco on June 8, 2023 at 12:40 pm

    Great idea

  7. Pablo Max on June 8, 2023 at 12:40 pm

    The TOH one seems a lot faster..

  8. Mary Roy on June 8, 2023 at 12:40 pm

    Great idea, think I could use a small one in my home…always so much dust flying around.

  9. DreamWeaver Ambient Sounds on June 8, 2023 at 12:41 pm

    Hate to be critical, but it doesn’t seem to me that a box fan would pull enough air to be significantly effective ? But what do I know..
    So, after having it for a while – how does it perform?

  10. Daniel Meecham on June 8, 2023 at 12:43 pm

    Thanks for sharing the idea. I’ve got some small window fans that I’ll make a boxs for. I’ll make them small and portable to use them for when I grind metal or cut wood.
    Thanks again!

  11. Rick Erickson on June 8, 2023 at 12:45 pm

    Thanks, I’ve always Ben thinking I need to spend hundreds for proper filtration. Also you explained well the hi volume low pressure vs low volume hi pressure. Been hearing that lately from other forums, and now I get it!

  12. Robert Huynh on June 8, 2023 at 12:47 pm

    I got a Holmes box fan – while it isn’t called the Hurricane like yours, I believe it’s standard. The thing is I was surprised to see that not much "suction" was happening on the back end of the fan and all I had was a 20 x 20 x 1" taped to it. Is this normal and it’s just my expectation was too high?

  13. SQ4ME2 on June 8, 2023 at 12:47 pm

    LOVE this. gonna build this asap

  14. Wild Woodworks on June 8, 2023 at 12:50 pm

    Great video to highlight the dangers of fine wood dust particles! Just a couple pointers as I’ve done many experiments with my own box fan filter:
    1. Charles Cox has pointed out to not overwork the fan. To add to that, clogged filters will actually force the box fan to pull air from the FRONT corners of the fan, just to blow it out the middle, effectively bypassing the filter media behind it. When this is the case, the box fan is actually counterproductive as all it’s doing is blowing dust around the shop.
    2. To avoid frequently clogged filters, use thicker filters than the standard 1", if possible. (I use 4" filters) Thicker pleated filters have more surface area of the filter medium and therefore can "collect more" dust. In practical terms, you won’t need to change the filters out as often.
    3. Try going to a local HVAC supply store (typically for professionals) and start a cash account with them to buy filters. I get mine for a fraction of the cost at big box stores.

  15. Sujith Srivasthava on June 8, 2023 at 12:51 pm

    thanks for the content

  16. David Blah - on June 8, 2023 at 12:51 pm

    If you buy a box fan make sure you get a warranty

  17. mike novotny on June 8, 2023 at 12:52 pm

    great video and great design.

  18. James S on June 8, 2023 at 12:53 pm

    Interesting tutorial for dust allergies but if you want to get it right, just get a powered airfared respirator, or have some serious air extraction blowing air into the rub as well as out. Also be mindful that MDF is a lot more harmful than certain woods. Good luck

  19. Jeff Sararas on June 8, 2023 at 12:55 pm

    How do you tell when the filter on the box fan is at the point of needing replacement?

  20. Mark Bryan on June 8, 2023 at 12:55 pm

    I use a similar system but with just one filter. It collects a lot of dust! However, I also vent my shop vac to the exterior of my shop. Even if particles get through its filter, they are vented outside and I am not stirring up the air in the shop with the exhaust. For those times when it is needed, (cutting mdf for example) I also have window fan built into the exterior wall of my shop. It is covered until I need to use it and it clears the air very quickly as indicated by my air quality monitor.

  21. Jeff on June 8, 2023 at 12:55 pm

    I like this idea. I watched vids about using cardboard to tape a three sided box together. Seems short sighted; when the filters get dirty you have to destroy the entire thing and rebuilt it which is kind of tedious to begin with. The old saw sort of: build once, cry once. Something like that. I don’t even need this. I cut everything outside of the shop and if anything, I can use the leaf blower or small fan to blow the dust away. If I do anything inside, I’m wearing a dust mask. I am way more concerned with my lungs than whether the shop looks neat and clean and when it needs cleaning, full respirator and leaf blower with all the windows and doors open. I don’t mess around.

  22. 111bobgato on June 8, 2023 at 12:57 pm

    Hi Mr. James what is the cart you are using at the end of this video? Is that a laptop cart? If you happen to have make/model would appreciate it. Thx

  23. Zancrus on June 8, 2023 at 12:57 pm

    I feel like you could have used door or window gaskets to seal the gaps so you did not have to keep redoing the tape on the filters in when you replace them.

  24. Luke Potter on June 8, 2023 at 12:58 pm

    Just duct tape a 20×20 filter to a box fan. Been doing it for a while.

  25. Ajinkya Badiger on June 8, 2023 at 1:00 pm

    Plant more trees as well🌱🌱🌱🌱🙏

  26. Daniel P on June 8, 2023 at 1:01 pm

    Should the fan be pointed toward you or away from you while working

  27. VAcreeper2022 on June 8, 2023 at 1:02 pm

    Great idea bro!
    Thx for the post!!

  28. Stan Kolodin on June 8, 2023 at 1:06 pm

    4:27. That’s why it’s duct tape, bc it’s for air DUCTS. You learn something new everyday.
    Why do I even go to college

  29. romney on June 8, 2023 at 1:07 pm

    A year ago I started home renovations and woodworking. I was really thankful for your video on air filtration, and built one that’s very similar. Since then I’ve realized my air filter really needs to be improved.

    It would be great to see an updated version of your videos, with a mobile air filter (that’s easy to transport) and a stationary version for the shop that can quickly clean the air of the smallest particles.

  30. Steven Hicks on June 8, 2023 at 1:11 pm

  31. 吳佑佑 on June 8, 2023 at 1:12 pm

    *Works amazingly **Fastly.Cool** . I love all the features and the double expansion. For once a fan is almost as tall as my window. Updated but not overly fancy.*

  32. CaptainSkelebones on June 8, 2023 at 1:12 pm

    i was just duct taping filters directly to box fans which i had 2 of. this i a little nicer looking

  33. Only Science on June 8, 2023 at 1:16 pm

    You can get a Lasko Air Flex (20×20 filter included) for about the price of the plywood

  34. Garbage_Media on June 8, 2023 at 1:16 pm

    are there any 3d printed clips for this

  35. khunsainam on June 8, 2023 at 1:16 pm

    simple idea, great explanation, informative useful video thanks a bunch

  36. Christopher Dekonstrukt on June 8, 2023 at 1:17 pm

    Yes it is very helpful. Use a garage and a back room as my workshop and tired of dust all over everything.

  37. mromutt on June 8, 2023 at 1:17 pm

    I made a dust collector out of a few 5 gallon buckets, lining up the perfect spinning airflow for the intake well also being two buckets tall made it so no dust making it out of the bucket system into the shopvac (actually never have to empty or clean the vac itself but I keep checking it anyway even though nothing ever is in there lol).

    But I do have a box fan hanging from the ceiling sucking up with a filter taped (and sealed with vinyl tape) so it sucks up into the filter then blows against the ceiling and then back down circulating. I regularly vacuum the dust out of it though just to make sure im never taxing the fan. I find it very useful on just about any project sanding, staining, painting or even just using windex lol its good about fumes and smells, I avoid anything toxic as much as I can since I can only wear masks for extremely short periods of time but even non toxic/non fine things are still bad to be constantly breathing in so a box fan filter is a must in my opinion!

  38. AngryZombie808 on June 8, 2023 at 1:18 pm

    2 in 1 air filter fan absolutely love it.

  39. Robert Foust Resto-Rob on June 8, 2023 at 1:19 pm

    Awesome! Thanks for the I formation. 👍

  40. Ryan Koza on June 8, 2023 at 1:19 pm

    Covering the corners of the fan (outside the circle)will help increase the draw

  41. Aaron Sivertson on June 8, 2023 at 1:19 pm

    I’ve thought of a slight variation to this for the basement workshop, so I can hang it from the ceiling – essentially to make the angles of the trapezoid much stronger angles, so the whole thing is much shallower, and hang it from the joists right above my work table.

    Any thought as to which way the fan should go? You have it drawing through the filters here – i.e. blowing air out of the box – and I’ve seen others do it the reverse. I think sucking into the box (blowing out the filters) is better for being less obtrusive while working (not blowing air at me constantly), but it is drawing dusty air through the fan motor – surely that will reduce the life span of the fan. But for $35 for a fan, maybe not a huge deal. Thoughts?

  42. Gonzo on June 8, 2023 at 1:19 pm

    I wonder if an air ionizer can help with dropping the dust. If you know an HVAC guy theyd probly be willing to just give u an old blower which can really suck. So if u wanted true hepa filters they will work with them.

  43. jafinch78 on June 8, 2023 at 1:24 pm

    I’m wondering how the 2" and like I just made a video detailing my 4" free design (minus the cost of tape and expense to get) compares. Seems a thicker and larger filter will improve airflow and filtration rate.

  44. CaptainSkelebones on June 8, 2023 at 1:25 pm

    very nice, using 2 filters in a triangle formation. genius

  45. Brandon Dennis on June 8, 2023 at 1:26 pm

    That’s gotta be really heavy

  46. Clutch 5sp on June 8, 2023 at 1:26 pm

    I appreciate the clean look you have about yourself. Everywhere we see some dooshy guy trying to be hip & cool with the dirty face pube beard, cap with sunglasses hooked on top and language using words like "sick"….etc

  47. Jeff Tran on June 8, 2023 at 1:28 pm

    I wanna build something like this that can attch to a small badement window. I want to exhaust the smell and dust outside. Do you think building something like this and channeling it, whether with wood or even a slinky duct would work? Only one eay to find out and tweak lol. My workshop/lab needs it to filter sawdust and animal smells.

  48. Josh DeMarco on June 8, 2023 at 1:29 pm

    Very nice!! When you turn the fan off, does some of the accumulated dust just fall back onto the floor once the suction is gone? Would it work as efficiently if the fan was turned the other way and blowing the dust into the box/filters, so when you shut it off the dust could just fall into the box and be shop vacced out later?

  49. Felix Rivera on June 8, 2023 at 1:29 pm

    Not sure if you’ll see this, but wanted to let you know about the “C-R” or Corsi filter. An earlier comment here mentioned a filter system on “this old house” that used 4 filters in a box formation—it’s that. Two university engineers came up with it and it’s been shown to work as well (if differently) as commercial systems.

    Basically: if you needed more affirmation that this is a good idea and of your own clever resourcefulness—engineers say you’re right.

    Though I’d also be curious how you’d improve your own design from some of the reasoning behind theirs. For example, commercial systems are more efficient—cleaning 80-90% of particles—but your approach is just so much faster that it can compete with them at a fraction of the cost.

  50. Pixie Doodle on June 8, 2023 at 1:30 pm

    more effective than a Dyson?