Black film?

We have a window literally next to my Glowforge plus where it’s vented out of, but the handyman told my landlord that it’s bad for the house and causing a black film to come in through the air conditioner. My air conditioner was replaced last week because the air filters were black and I was having to replace them every few days. Now I’m being told that I need to move the machine outside (which makes no sense) or to the garage. I live in the southwest where we reach 100+ temps. My garage is not air conditioned, nor does it have a window to vent.

I’m at a loss as to what to do to. I’ve been using the machine for a year and a half and the black film on the air conditioning filters has only started happening in the last 6 weeks. I cut every Monday from 4-6hrs and Tuesday-Friday for about an hour and a half. I work all weekend, so I never cut on Sat-Sun.

The electrician suggested an inline fan, but it would still be vented outside the same window. Can it really make that much of a difference? I’d hate to spend the $1000 on the Glowforge air filter if I can avoid it.

Any advice is greatly appreciated!

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An inline fan would make the expelled smoke be much thinner, but unless the AC is importing air from directly down wind of the exhaust there is no way it would make much of a difference. It would also be my expectation that there would not be a lot of exchange with the outside air with such a difference in temperature outside.

I would also look about for a better expert than that handyman. :roll_eyes:


That’s exactly what I tried to explain to my landlord. We live in a duplex and they are putting on a new roof too, but since they can’t figure out what is actually causing the black film, they want to automatically blame the cutter. The electrician said the cutter “could” be the problem, but he was in the house for like 2 minutes and not when the machine was on and cutting.

Thanks for your response!

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If youre having to replace the filters every few days, how about if you put in clean filters, wait several days without using the gf, then check the filters? If they are clean, resume using the gf and then check again. That will tell you if it’s the gf causing the problem.


unless the GF is venting right next to the air intake for your AC (not necessarily the external unit, but where the air is being pulled into the fan inside your house), it would be almost impossible for it to clog up your filters.


That’s literally what I was just discussing with my husband. I haven’t used the cutter since last week because the roofers detached the satellite dish for my internet. I’m going to look at the air filter in the morning. Thank you!

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Thank you for your response! The air conditioner is on the roof. We are in monsoon season with lots of wind and rain, so I just don’t know what to think anymore.

What have you been cutting in the laser? I’m having a hard time seeing the laser venting leaving a black film. How about an exterior picture of the vent in relation to the air conditioner condenser.


Sounds really, really, unlikely. I’ve never seen any soot or smoke traces next to my vent.

Has anyone ever seen soot or smoke traces by their vents?

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Are you getting smoke from the western wildfires in your area? If so I’d guess that’s far more likely a culprit then the GF unless your exhaust is right next to your ac intake (which you wouldn’t want anyway).

I vent out my window screen and do see an exhaust hole shaped residue patch on the screen. Mostly cutting BB ply and acrylic.


This whole topic is confusing me. Air conditioners don’t bring in outside air. So the premise that your GF is venting something that’s being sucked in by the air conditioner is invalid. The handyman should know that. The stuff that collects on your AC filter comes from your indoor air.

It is still possible it’s your Glowforge, since the exhaust could be leaking into the house. Do you smell smoke when you’re using it? Has the ventilation performance dropped lately? Maybe it needs a cleaning, or maybe your duct is loose somewhere.

Any chance you’re using candles in the house? I had that exact thing (filters turned black) and I realized it happened after I had burned a candle. That’s when I decided I don’t need a source of soot in my house and lungs.


I cut 3mm Baltic birch, acrylic, and leather. I’ll try to get pictures before I go to work. I vacuum inside the laser before I even turn it on.

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Actually I do burn a lot of candles and incense. My business partner makes them with essential oils.

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Yeah I felt the same from the start. Either something isn’t clear here or someone’s mistaken/full of it.

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I don’t see smoke in the house while I’m using the Glowforge, but my husband says when he comes home, he can tell I’ve been using the machine. I guess maybe I don’t have my venting out of the window properly sealed. If I don’t have it sealed properly, do you think it would cause the black soot/film that’s in the air conditioner filter?

About 2 months ago I removed and replaced the vent tube and cleaned the fan.

Sorry, it’s so hard to describe without showing everything we’re seeing so I know it’s confusing.

My gut feeling is no. I have my Glowforge in a room with a ductless mini-split air conditioner, and I can smell the smoke when it’s running. Despite that, I have no residue on my AC filters.

I think it might be the candles. They produce a lot more soot than you might realize and if you have nice white pleated filters in your AC, they might be collecting it. I think the Glowforge vaporizes more than carbonizes.


I am with the confused crew on here.

the facts as I understand them.

  1. the FILTER INSIDE your AC UNIT is turning black with some kind of film/soot/dirt what have you?

  2. your Glowforge is vented to the OUTSIDE through a window.

  3. the venting “hardware” of the GF is NOT leaking. all joints taped.

how HVAC systems work.

the air gets sucked out of the living space via return ducts that lead to the filter.
the air passes through the filter then through the heat exchanger(only a factor when heating) and then through the AC coil which cools the air and then blasts it to the rest of the house.

Now I know that is simplistic, and widely known. I just wanted to make the point of reference so when we all sit here going so how is venting the GF out the WINDOW. causing anything to collect IN the AC unit’s filter.

to be clear and to your husband’s point you can tell that you’ve been running the unit. because when you pull the completed cut out of the GF you get a little smell from the air inside, and what you pull out Stinks too. so he could be smelling that.

I am agreement with Chris1 in that unless your venting setup is completely terrible(unlikely because you’re not saying “HOLY CRAP IT STINKS THE WHOLE TIME I’M RUNNING IT”

Has to be the candles producing a lot of soot. you could take the return register covers off and wipe a white paper towel inside on the ductwork and perhaps get some idea. how close is the candle burning to the return closest to filter?

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See also 3 Reasons Your Home's Air Filter Is Turning Black | Energy Air, Inc.


Not sure where the OP lives, exactly. But the handyman may have heard on the news that most of the west coast is on fire and that heavy smoke is drifting slowly across the entire country. I would suggest that may be the reason why your AC filter is black. The air has a pissload more dirt in it this summer.

Also, I guess I’d be highly suspicious of a handyman who replaced an entire AC unit because the filters got dirty. Seems like replacing the filter would be the right course of action. If the GF truly is to blame, just suggest that you’ll pay for the AC filters yourself. The handyman can show you how to replace them, and you can probably buy a caseload of them at Home Depot.


And sand and dust beyond most of the country. I recall that my mother was going nearly crazy every day when we moved out there as she could dust and need to dust ten min later :roll_eyes: Mold is not a likely issue, but western fires, much more likely. in any case, they seem to be making an issue just to make an issue.