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HEPA/Carbon Air Cleaner / Scrubber

by RJ_Make Feb 5, 2016
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Apologies if this has been answered already in one of your videos, but I'm looking to use this in an enclosure with my Prusa i3 MK3. Do you think the air needs to be ventilated out of the enclosure? I wanted to just set this up in a sealed enclosure and recirculate the air. Then when the print is completed, let the scrubber continue to run for 5-10 minutes longer. Do you think this will be adequate?

There are some studies that suggest continuously recirculating the air through the HEPA filter will actually allow the HEPA to capture much more of the UFP then it would otherwise. So it may actually be better to not exhaust the air from the enclosure, well at least not all of it.

You may want to hold off on printing this as I've completed a newer version (complete redesign), one in which I think should work better. It's based on a good HEPA/Carbon filter that is in production and cost less then 15 bucks. I will be releasing everything once I've completed my testing. If you don't want to wait then you should print this re-mix as it's easier to print then mine. https://www.thingiverse.com/thing:2394452

HEPA Filter for 3D Printer

I am interested in your redesign of your filter system. Have you finished it yet?

It's finished, just testing now. Hopefully will be releasing sometime in June/July.

Did this ever make it out of the testing phase?

C_HAZE -- Yes and it failed miserably.. :-( I'm working on a new design that uses a different base cartridge and more carbon, however I have discovered something very important in my testing.

It seems unless the design utilizes a very large amount of carbon, (+10lbs) the scrubber can not keep up with the rate of VOC emissions. That includes this design, and I suspect other small frame scrubbers.

So it seems the only effective solution is to have a sealed print enclosure and a effective filtration strategy. I think the filtration strategy (when and how long) is going to be the most important aspect of getting the air cleaner inside a sealed enclosure.

From my prior testing, carbon definitely works at lowering VOC's but the required run cycles to accomplish this with <10lbs of carbon are not encouraging so far.

Once I complete and populate my new 'print tower' testing will resume.

Do you think a different type of filter would be more effective than using carbon?

I am not sure how the various 3M respirator filters work but maybe they can achieve similar levels of filtration without requiring such a large form factor (10lbs of carbon).

It is unlikely, volume seems to be the limited factor. That said, I ordered in some ZEOLITE to see it's effectiveness. The 3M respirators have MUCH denser media (which causes the high pressure drop issue) but at this point I think what I saw was simply related to VOC volume vs carbon volume.

Great idea and design but i have a question. I have Tevo Tarantula and just finished to make my custom build IKEA Lack cabinet and looking for airflow and ventilation. Where do you actually locate that filter - is it inside box or outside? If it blowing filtered air out where does it get incoming air from? As understand box has to be completely sealed. Can you put please few photos of you box intake and outtake ventilation holes. Thanks

Check out the testing video, it should explain everything.

Oh and by the way, I've just completed V2 (it's a complete re-design), of the scrubber and I'm VERY happy how it turned out. It's based on a good HEPA/Carbon filter that is in production and cost less then 15 bucks. I will be releasing everything once I've completed my testing.

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hi, this question migh look "ignorant: i see your measuremnts about air flow , in wich units are those measurements? because it is imposible to move 195 cubic feets/minutes of air with these fans...if your units are not cubic feets/minute can tell me the equivalent?

It's not 195 CFM, It's 195 FPM.

I like your project, have some questions:

  1. Does the system you make have enough power to capture all smell/ABS particles if I put near my bed printer (but no enclosure)?
  2. What do you think to mod your project and capture the fumes/ABS particles trought a connected PVC pipe (10mm) directly near the extruder?

Also, where do I need to put active carbon pellets?? I cannot see in the video... and I think to put inside "filter body bottom" until it's filled, but left or right side??

Thanks man


1) No. I think it's barely enough with my setup on the Flashforge Creator Pro.
2) You would need to find a pretty powerful fan motor, considerably more powerful than anything discuses in these comments.
3) Yes, inside the main filter body, below the HEPA filters. If you use the divider, fill the motor side, if you don't use a divider then just fill the entire lower chamber. In both cases you need fill and level off right under the HEPA filter edge. Not sure why you can see this in the video, it's pretty clear I thought?

I'll take some tests in the next few hours about a system "10mm pipe"->"Fan duct"->"Fan vacuum cleaner mode" to see if can be modded your project (maybe with delta @ 12V there're enough power)

And yes it's clear also for the carbon pellets fill mode.. I think I understand how to proceed to filling the part "main filter body" with the divider placed inside.

Thanks for sharing

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How does a noctua fan work in the build - did somebody test it (or maybe using push-pull with two of them) ?

I have the tools to test, but I don't have the fan. If someone want to send me a fan, I'd been more than happy to run the tests. ;~)

Would it help in air flow if you have two fans blowing in both ends?

At the time, I didn't have 2 fans to test this.


What are the final dimensions of this filter? Want to make sure it will fit within the enclosure I'm building.

8-7/8" Long x 3-1/4" Wide x 4" High (Includes the motor)

no reply for my question?????

Sorry, but I don't have an answer for you. I know that ategro (see his comments below) was thinking about using that fan, but I believe he took a different route in filtration.

Can you clarify where that new extra piece gets glued exactly? Hard to tell from your image. Dies it glued underneath the filter edge against the grate? Thanks.

It gets glued in underneath the filter edge. The filter edge must remain even all the way around the chamber so the filter foam can seal against the edge. If you need further help let me know.

Would you confirm me if I can use this fan instead of the one you indicated!
I understand that it is much less noisy!
Expect your kind reply


So this will scrub the air from inside the enclosure (that is to be airtight) and blow the scrubbed air to the outside? Wouldn't that create a vacuum since the enclosure would be sealed? Or am I missing something? I would love to adapt this to my printer and enclosure.

The goal is to create a slight negative pressure gradient inside the printer , No matter how hard I tried I could not get my FFCP 100% sealed. So it never creates a vacuum.

Did you consider having another fan pumping air into the enclosure, very much in the way pc cases create negative pressure inside.
I am using your filter design for a custom enclosure i built so i can afford to just drill holes here and there i don't know if it would help on your printer enclosure.

I had not, but I don't think that would help in my situation. The printer cabinet for the FFCP is just too 'drafty' to pull warm air from the bottom.

Just a thought. The Delta fan in your link has a static pressure of 2.129 H2O. The Noctua NF-A6x25 FLX (http://noctua.at/en/nf-a6x25-flx) has 2.18 H2O static pressure but is much, much quieter. The CFM on the Noctua fan is obviously much smaller, but if its pressure that's the most important, wouldn't this work?

I think so. The delta moves an incredible amount of free air, but you are correct static pressure is our enemy. That said, I don't think the noise level reduction is worth the cost of the NF-A6x25 FLX. That is one expensive fan.

It's around 20 USD (converted) here in Europe (seems to be available for 15 USD on the US amazon too). I'd say that's worth it for near silent operation :)

Not gonna hang you up on it if it does not work, but it's perhaps worth a try, eh?

Indeed worth a try. Please let me know how you make out with it if you don't mind. This is what I saw when I looked it up: https://www.amazon.com/Noctua-NF-A6x25-60x60x25mm-1600-3000rpm-Bearing-/dp/B009SR1EQU/ref=sr_1_2?ie=UTF8&qid=1470833969&sr=8-2&keywords=NF-A6x25+FLX

Looks like it's a 3 pack, I missed that before.

My enclosure is not entirely air tight so take it with a grain of salt, but it seems to be working really well and is near silent at 12V (still pushes plenty of air). I don't have an anemometer to test with unfortunately. I'd love to see how well it scores. I'll report back with some (still subjective) findings when I get the enclosure completely air tight.

I don't know if this is the PWM or the FLX version: https://www.amazon.com/Noctua-60x25mm-Blades-Bearing-Premium/dp/B009NQMESS/ref=sr_1_1?ie=UTF8&qid=1470834132&sr=8-1&keywords=Noctua+NF-A6x25+FLX
but either model provides the same static pressure so I guess it shouldn't matter. Much cheaper.

And yes of course, I'll report back with my findings. It'll be some days before I get to it.

The maker bot top link seems to be broken. Is this the product you used https://store.makerbot.com/parts-accessories/x1-rep2x-top-enclosure/ ?

Yes that is the correct one.

How did you get the cable and filament wires through this new top? There is no opening to allow cables through. Did you drill holes?

The rear is designed to allow the filament and extruder cables to operate freely. The rear sticks out past the frame of the printer. Check out one of the testing video's on my channel. I think one of them will show you what I mean.

Hi and thanks for making this

I have some questions if its okay.

1) Why is the HEPA filter needed? I have a respirator cartridge from the original design - will that not work?

2) I have an unenclosed printer (TAZ 5) I've built an enclosure for. So the printer stands inside a big MDF box. I was thinking of just placing the air scrubber inside the box and let it do its work there. However, the challenge is that the control box needs cold air intake for cooling. So I've made a hole in the side with a duct leading to the control box to remedy this. While this does the trick, the problem is obviously that this hole allows toxic air to escape. I fear that placing a filter in the duct will result in the intake airflow being restricted too much, overheating the electronics. Is this possible to solve in a sensible manner?

Thanks for your time

1) In my testing I don't think it does work. (See my testing video). My design, which moves significantly more air barely works.

2) Is the printer located in a room that you can exhaust the air out a windows or such opening?

Do to the natural convection taking place inside a print enclosure, the most effective way to remove the fumes is to filter (or exhaust) from the very top of the enclosure. In my testing it's best to create a slight negative pressure gradient inside the enclosure. If you can simply exhaust from the top, out a window then you will not need to scrub the air.

In the next few months, I'm planing on doing a complete redesign of my scrubber to take advantage of filtering from the top, instead of the current design.

Hi, I liked the design concept and made one of these but I think i've found another couple of flaws in the current design.

Firstly, the second grate that you have, in the middle, being circular, doesn't really have a purpose that I can see because the second flaw is that there's very little reason that any incoming air should go down into the carbon pellets before turning through 90 degrees and then traveling horizontally towards the fan. I suspect that an analysis of airflow would have it just passing through the HEPA filter and then along the top of the carbon before diving below the extra little plate and out via the fan.

To try to avoid this, I made an additional piece to fill the gap above that middle grate and then I left the closed half of the chamber empty. I then used the end of a pair of my wifes tights ("hose" to you lot over the pond ;) ) and put some carbon granules in that. I didn't fill much of the space before I found that airflow was impeded.

I'm pretty sure that a better design will have the HEPA filter opposite the fan such that airflow MUST pass through it then a charcoal area before passing out of the other side and not allow any short circuits. I'll probably mix one up because i've got all the bits now but wanted to feedback my thoughts.

Great points, and perhaps you are correct, at least in part. I will assume you saw the testing video's I made? I did test the airflow with just the HEPA; then with the Carbon in place. As you can see there is a significant CFM drop with the Carbon in place, 'magnitudes' more over just having the HEPA in place.

This leads me to believe there is potentially more air moving through the Carbon then being bypassed. At the very least the amount of carbon that is active can be measured from the bottom of the gasketed HEPA support and the top of the 'suction' port of the chamber mouth, but I suspect much more is active.

I do agree, a completely 'pull-through' design is way more efficient, but space is extremely limited inside the FFCP. The next design will be a top mount design (through the top lid) that should be far more effective.

The middle grate is completely optional. I added it in the case of using a desiccant or splitting the Carbon volume.

I did see the videos yes. As I said, when I filled the end of some nylons with charcoal, only a small amount at the throat of the filter would cause a significant flow drop.

I've uploaded some pics of my make and you'll see what I came up with as a modification. I am also using mostly fish tank charcoal foam which is very open and free air flowing and then in my extension piece, I have a sandwich of charcoal foam, charcoal and charcoal foam again. A bit experimental but i've loads of airflow with this and I used my "Mk1 Ultra Sensor" (aka "wife") and she couldn't smell my printing odours seems to be a good result :)

Ah nice, I better understand what you did now.

If I'm reading this correctly, the HEPA filter filters down to 3 micron, but we're talking about 1 micron particles? Wouldn't a lot of them get through the HEPA filter regardless then? Just trying to figure out how safe this is.

Yes, but the hope is the carbon will pickup the harmful stuff.

Thanks for replying so fast :)

I can probably exhaust the air out of a window. I'll look into that. I just fear it'll get too cold to keep open in the winter.

About the intake hole, is there a way to make it "one way" so the toxic air doesn't get out? Or is some kind of filter needed there also (It'll just block the airflow too much I fear)? If I don't let the electronics have cold air in for cooling they will overheat within an hour.

Did you ever solve this? I'm looking to make sure toxic air doesn't escape either, and am similarly located in a winter climate. Did you succeed in making it "one way"?

I did. I used an 80mm noctua fan (can't recall which one, but the PWM version that has the highest static pressure. They have an overview on their webpage) and two foam carbon pads to make an exhaust on one end. The intake goes directly to the control box on the printer. The exhaust moves slightly more air, even through the filters, so the negative pressure keeps all the toxic air inside until it has been cleansed. It works very well and I can't smell anything even after 10+ hour printing sessions while sitting right next to it. Send me a pm if you want more information :)


I'm thinking of also creating a scrubber, though am wondering what active carbon filter to use.

I notice on commerical enclosures such as the Buzzbox they use, what looks like, quite thin carbon pads - as opposed to a much thicker filter that you'd find in something like a vacuum cleaner.

What filter(s) did you end up using?



Hi there

I'm sorry, I don't remember the specific brand, but I use two activated carbon (they have to be activated!) foam pads from a local aquarium store. They're about 1.5cm thick each and I stack them on top of each other, fitting them tightly into the mount I have for then in my enclosure exhaust vent.

For reference, holding one of the pads up towards a light source and looking through it, you can see light coming through. Holding both of them on top of each other and it's pitch black.

It's time to replace them, too, as the smell isn't filtered anymore, so I'd say they last about 2-5 months depending on usage.

How do you connect the fan to to power supply?

Added Assembly Video. Please let me know what you think Youtube

Did you ever try a push-pull configuration with the respirator filter?

Is there a reason to vent the air out of the box instead of just recirculating?

Love your design by the way. I always feel like my 3d printer aggravates my lungs and any filtration is better than none.

Hello Nutmegz,
I did not test a Push/Pull setup (using 2 fans motors; one pushing and another pulling) as I only had one fan motor at the time. I have more now, so that sounds like and interesting test. That said, I did test pushing air through the respirator and the results were worst then pulling.

My thinking was I would get better results (attempting to process most of the air inside the build chamber) if I could create a slight negative gradient inside the build chamber. As it turns out, it is one of the most difficult things to achieve (impossible for the FFCP). That said, with the chamber sealing mods I've implemented I have been able to burn a incense stick inside the printer and only get slight hints of the smell, so I know it's working to some degree,. :-)

It may be that a recirculating implementation would work, but I don't know how to test it's effectiveness. recirculating would give the added choice of using some desiccant in a divided chamber setup. (the carbon reservoir can be divided up into section)

I'm about to do another air flow test on the scrubber, once I hit 20 hours of printing. I'm currently at 15. I'm interested to find out how much the air volume has been reduced.

Thanks for your kind words.

Could you make a version for using pvc pipe? Reduction in build time would be very useful. After playing the game "the Division" this made me wonder about air filtration for biological issues and this design looks incredibly useful.

Could you elaborate on your proposal? My biggest concern would be how to easily cut the PVC pipe to receive the HEPA filter mount.