Odor/Venting Questions


We just got and GF basic and are very excited about it, and we’ve had some good prints already and some very helpful replies in the forums. But we are getting more odor than we would like in an extra room in our basement. I don’t believe this is in the category of “problem”–there’s not a lot of smoke or anything visible in the room or something that seems disturbing. But we’d sure like to reduce the odor. I’ve been trying to track the many venting threads, including those the reference external fans, but I still have lots of questions, and I’m hoping you might help.

In terms of our set-up, we’re venting out an egress window through a piece of plexiglass with a 4" hole in it, and we’re about eight feet of ducting from the back of the GF to the window. I know that I need to do a better job of sealing the plexiglass against the window, which I will do with some insulation. I also need to do a better job of sealing around the duct that runs through the plexiglass. I suspect addressing those issues will help. In the meantime, I am wondering about the following:

I’ve read several suggestions about various types of ducts that seem to be better than the one that is included because they are somehow quieter and less likely to let smells escape. I was thinking that I should go with this one or this one, though there was some debate about whether or not ducts that have a layer of PVC add to fire risks or maybe make any would-be fires worse. I’d be curious what your thoughts are here and to what degree that might help solve some problems.

I was also reading that external fans are a useful addition, but I was little unclear about three things:

Is the idea to run the external fan WITH the built-in fan? Are there any risks to that? Does doing so compromise the warranty? I wasn’t clear if there was an internal fan shut-off that people switch off when using an external fan.

What size fan should I be using? Initially I was going to get something like this. But some posts suggested I need one that is at least as strong as the GF built-in fan (which I think is 200 CFM?) so as to avoid air actually being sucked backwards into the GF. Is that correct? Any recommendations on the fan? Ideally it would 4" but I don’t know if that’s doable. Again, we’re only going about eight feet with a couple of turns.

Finally, ff the addition of an external fan is recommended and doesn’t put anything else at risk, is it best to put it closer to the machine or perhaps into the plexiglass at the window?

Thank you for your thoughts here.

You’ve definitely done your research! I kept on waiting because I wanted to be sure I was doing it right - and the only thing I regret is the almost a year of noisy lasering :stuck_out_tongue:

I’m currently using your first option above, and previously I used this one; both work well, the first one is a little easier to deal with because it doesn’t have the thick insulation so I’d say go with that one.

I am using two of these, but a single one worked just fine. I “upgraded” to this 6" one and it was way louder and no better at clearing the air so I went back to the 4" and put one right at the rear of the :glowforge: and the 2nd at the window. I can’t even smell acrylic anymore. It’s lovely :slight_smile:

The switch to turn off the fan is in the GFUI here (this being on means the fan is off):

Doooo eeeet!! You’ll be happier :smiley:


I use a 4" rated at 190 CFM and it works quite well.
The compunds in the vent hose make no difference because you are not burning them.

If you are venting out a double-hung window there will be an opening at the top of the bottom half that needs to be sealed.

If using a booster (highly recommended) placing the fan as close to the exit as possible will create suction along the entire length of the vent, so any leaks will be pulling air in.
If the fan was located at the machine the exhaust run would be pressurized so any leaks would be pushing smoke out of them.
As @deirdrebeth said, when the leaks are stopped there is zero smell,. And it is indeed lovely. :kissing_heart:


Thank you to both of you for the information. It’s very helpful, and I’m ordering pieces accordingly.

From what else I’ve read it sounds like I can use both the external and internal fans simultaneously, depending on how much smoke, and I appreciate your showing me how to turn off the internal fan.

I look forward to more quiet and less odor, and I’ll let you know how it goes.

Thanks again.

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Two things on the internal - keep in mind you can only turn it on or off when 1) your system is on and 2) before starting a cut.

Plus once you hear how quiet it is without the fan you’ll likely never turn it on again!


I highly recommend the AC Infinity Cloudline S6 6" inline fan.

I’ve been using mine with my Glowforge since 2019, and I am a pretty heavy user. The S6 is a hardy fan, well-built, quiet, easy to take apart to clean and goes back together without issue.

I have seen too many complaints about cheaper 4" fans that (1) aren’t air-tight, (2) fail or leak after a few months or after cleaning, or (3) don’t achieve anywhere near their rated CFM so they don’t clear smoke well or the Glowforge starts overheating often.

My vote is to get a 6" fan at minimum. You don’t have to run it at 100% speed. The bigger the fan, the quieter it’ll be moving the same volume of air.


I bit the bullet too and bought the fan and duct. Currently I use large, uncomfortable sound-dampening ear muffs. It has to be better than that. Let’s compare notes on how we like it.

I recorded this (terrible) video when I finally did my set-up - you can hear just how quiet it is :smiley:


Well, I ordered one 4 inch fan, though I appreciate the additional recommendation and consider myself well-warned regarding the possibility that I’ll ultimately have to do 6 inches.

Good to know, too, about on/off timing for internal fan. It sure sounds quieter without that internal fan going!

I’ll be happy to compare notes soon and hope to have everything in place in the next couple of days (If I don’t, my son will not be happy with me.)


I might be going with your setup. What do you recommend using as a 6” to 4” converter. For what I can see in your picture you have two (one on each side of the fan)

Last question is- do you run the glowforge internal fan along with the 6 inch booster or you only run that one.

Thank in advance for your time. My glowforge is coming in about a month and I want to be ready :slight_smile:


That is super quiet! Love it. I’m mostly going to be cutting acrylic and I’m scared of the possible smell haha.

Thank you for sharing


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The 6" to 4" reducers came from Home Depot: https://www.homedepot.com/p/Master-Flow-6-in-to-4-in-Round-Reducer-R6X4/100111736

I only run the inline fan, not both.


Thank you for your time and response.

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What a difference this external fan makes! I don’t need the uncomfortable ear muffs anymore. It is so quiet!

I am a happy camper. Thanks to all for your suggestions.


Hi, everyone,
I initially tried this fan that @deirdrebeth had suggested but found that it did seem to leak from the central seam. So I exchanged it for the 4" version of the one suggested by @dan84. It’s double the price but it’s a very high quality and efficient fan and seems to do the trick even though it’s not 6" (though we’re not cutting on nearly the scale that many people here are). Between the fan and the new, improved duct, we are quite happy. Thank you all for the suggestions.

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Oh I’m sorry you got a bad fan - I hope you returned it for a refund!

and yay on finding a system that worked :slight_smile: It’s SO nice isn’t it!

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Or use this

I have Tis and use a 4” to 6” reducer to my 6” fan. Works ok.


Yes, full refund, and yes, very nice new setup. Thanks again for your help.

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Well, I’m back because we recently got one of those air quality testers since we have kids and the GF is in our spare bedroom. And what we see is that even with our new seemingly great setup, we get highly spiking PM2 and AQI numbers when we run the GF using draftboard. This is true when we run the external and internal fans together, and when we just run the external fan. We’re also running a small hepa in the room.

The numbers are especially high next to the external fan, right by the window. But even beside the GF, the numbers are bad.

I’ve attached pictures of our set-up–the run is 8ft with a few bends to the fan at the window. Based on what I’ve read, I don’t think that’s too long, especially with both fans running. I sealed up all the seams on the fan using shiny silver duct tape in case that was part of the problem, but it didn’t help. I sealed completely around the plexiglass in the window as well, using the silver tape, and I also taped the backside of the GF .

I’m wondering where the problem could be at this point. Perhaps there’s some leaking around the hole where the fan is vented through the plexiglass–it’s not perfectly sealed because we have to remove the fan when we’re done printing to close the window and put the screen back on. But as you can see I did put some insulation around the venting duct so as to get it pretty tight.

Maybe it’s the plexiglass itself, which is somewhat thin, 1/8 inch–I had my hardware store cut it, and I could have gotten a thicker version–but it doesn’t seem like that could be the problem as I’m not sure how even with thin plexiglass the smoke or whatever could be coming through.

I’m wondering if there is a problem with the external fan (I exchanged one that was obviously leaking air for this one, though that was before I had the air quality tester so I have nothing to compare to in that regard). Or maybe there are pinholes in the duct, but I bought a higher quality one as per the recommendations here, and it seems unlikely (and besides the numbers spike up, as I say, even with just the external fan, which would suggest it’s not a pinhole issue).

Just a note: usually, when we aren’t snowed in (which is mostly the case), the window is open completely. Also the tape on the duct is just because it’s longer than we need and the tape keeps it together.

I’ll be curious if anyone has any good ideas or suggestions. This is quite a mystery to me at this point. Thank you!

First thing I see is a wide open window that everything can waft right back into. Might want to toss a few feet onto the other side of that fan, put the fan further out the window, or you’ll need to create a window insert that creates a barrier to prevent the backdraft.

Edit: Wow…that is some clean plexi-glass…nevermind. nothing to see here…literally. move along, move along.