No. It’s a non-issue for me, as the fan is only operated while I’m using the machine.
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Perhaps others have those problems but I wish I had those problems in anyplace I have lived (though mostly in Florida)
For a bit more than triple the price of a Vivosun 4" fan you can get a Cloudline 4" fan and an extra 10 CFM
Thank You for the feedback. I’ve wanted to do this for a while and I think I may just pull the trigger.
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I think I am going to do it with the 4" hole but If I were to enlarge the hole I think I would either try to make a circular blank to the size of the 4" hole so I would have center point for the pilot drill on a 6" hole saw or nail a piece of plywood to cover the 4" hole and create a guide for a 6" hole saw. Might still be sketchy though.
As is mine. But as soon as the fan stops the negative air pressure pulls residual fumes back into the room - not to mention humidity and pollen from outside into the GF. Maybe that’s not an issue for others but where I live all the oaks are in bloom and the cars are all yellow. When I noticed some pollen inside the GF it was a bit of a revelation for me about negative air pressure.
I live in Atlanta, I’ve never had this issue.
If you’re going to expand a vent, you’re generally better off cutting square holes, and using a flange/vent cover of some kind.
It all comes down to how the walls are constructed.
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@eflyguy Good idea. I also think @tjleasa’s suggestion for enlarging the hole could work, if the plywood was mounted on one side of the wall, and the hole was drilled from the other. That way the plywood would continue to support the pilot drill as the hole was being cut. I think I’ll try that first, if all else fails go with the square hole & cover.
i haven’t had this issue either. but i live in a 70 yr old house, so i’m guessing my house is probably a lot less pressurized than a lot of newer homes.
that said, if you have this problem, an external fan will be your best buddy. because you can just leave it running until you know there’s no smoke/fumes left inside your machine. you can let it run for a couple of hours after you’re done, even.
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Yeah, the house I grew up in, also in FL, had jalousie windows and the household envelope was as porous as a screen door. My current house is 2003 vintage and “energy efficient” means “tight envelope”. When they first tried to sell me on the ERV system I was skeptical but now that I can see and feel in inbound draft through the GF duct I realize there was something to it.
I’ll probably follow @shop’s suggestion and use an outboard fan that I can set up to run for an hour so so after the print stops. Then I can disconnect the vent right when I turn off the fan so no pollen or humidity gets sucked back in.
Thanks for the feedback, folks.
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i use a blast gate on mine (although i rarely close it and it has the vent louvers outside to keep any varmints from coming in when the fan isn’t running to keep them open). i’m not sure if that seals enough for you, but it could also be an option.
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Hello Where did you get the white extender?
there are some 3D files floating around here, so if you have a 3D printer, you can make your own.
i don’t, so i purchased it from someone on amazon.
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I have a dryer vent hood on the outside with a flap and a varmint cage. When my window fan is creating positive air pressure, the flap floats out a half inch and a draft can be felt. When I don’t have the window fan running and negative pressure from GF, dryer, bath fans, etc., the air flow is sufficient to pull the flap closed. I propped it open and ribbon tested and there’s quite a bit of ingress.
Unfortunately, the vent flap doesn’t seal well so I also borrowed from my wood shop. I used a 30x20 sheet of 1/2 UMHW, some T-Track and some clamps. I then printed a cap that seals tight for when the GF hose is disconnected. I don’t know if it seals better than a blast gate but it seals well enough that the smell from the print room doesn’t infiltrate the rest of the house anymore when we have negative pressure and I cap the vent.
In any case I’ve ordered an inline fan as per other suggestions and will keep using the window fan until I have another solution for equalizing indoor pressure. Surprised it isn’t a well known issue with some canned solutions but I’ll come up with something. Probably from my wood shop downstairs. 
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You may just have one of the better-sealed houses of all GF owners. 
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Here’s one source that says a 45-degree bend is equal to 2.5 ft of straight pipe. A 90 is equal to 5 ft. It also mentions make-up air, which is a concern particularly if you have a non-sealed source of combustion (non-airtight fireplace or stove, low-efficiency furnace or water heater), or you live in a properly built newer house with an air barrier and sealing.
Dryer Vent Safety
Whole house heat recovery ventilators are the automatic but high initial cost way of providing make-up air. Opening a window is the low initial cost but you-have-to-remember-to-do approach, and if the outside temperature isn’t moderate it will cost to heat or cool that make-up air. There’s no perfect, easy, low-cost solution, it’s simply an aspect of laser operation that you need to accept. As with dust collection for woodworking, once you are part of the community you hear plenty about it, but manufacturers never bother to mention it because they want you to think you can just buy a machine, plug it in, and crank out amazing stuff. Hah! I can only hope there’s a special place with minimal make-up air for the people responsible for such deceptive marketing.
It’s not something to take lightly, but as long as you understand it and take appropriate measures there’s no need to panic. I raised it way back when the first discussions of venting were taking place here. A refresher - note especially Factor 3 in the section “When Things Go Wrong”.
Combustion Gases in Your Home – Things You Should Know About Combustion Spillage
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Wow, @whitehill, thanks! I was beginning to think I was making a mountain out of an air pressure molehill. I have some reading to do now.
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I would upgrade to a fan like this but I need one that can be mounted outside.
i feel like someone early on mounted an exterior fan with PVC pipe running alongside the house up above the roofline. saying part of why they did it that way was so that it looked like a radon thing, maybe?
Yeah, a radon fan may be my best option, and it was @dwardio.
I just posted a question on amazon about the cloudline fan and weatherproof-ness. I’ll report back.
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