That’s a good idea. Ironically I bought some incense sticks for just this purpose - when I was building my last PC and wanted to check airflow. However, my wife made me throw them out because they were stinking up the place. I guess I’ll have to get some more.
Does the GF unit itself leak fumes when the lid is closed? I’d like to understand if this is expected behavior, or something specific to my set-up.
That is the point of them isn’t it?
The inside of the GF should be under negative pressure so nothing should get out from the various cracks.
Do a search using the terms ‘@chris1’ and ‘leaks’. His sensitive nose lead him to banish all odors due to the GF. Here’s a start:
https://community.glowforge.com/t/airflow-measurements/11260?source_topic_id=14784 https://community.glowforge.com/t/let-s-talk-about-fans/10850?source_topic_id=14784Strange, when I click your first link, I get a message saying I don’t have access to that topic.
Bad link.
I’ve added links that work.
How important is it that I disconnect the Forge from the vent hose when not in use? The outside of the window attachment does have a flapper that closes when there isn’t air blowing. Can I just leave it connected? This would allow me to jetison this quick-disconnect, which I think is the source of at least some of the leaks.
The most common source of leaks seem to be at the connection to the GF and the connection at your window. The clamps are not very good at completely sealing out air leaks. A lot of us have resorted to metal foil tape at those two connections.
During operation air should be sucked IN through lid cracks. After the fan stops any residual smoke or smell could enter the room but should not during operation.
I have never ever disconnected my hose from the machine or wall. I live in the mountains of WV with cold temps and have been using the unit since late February. Like you I have a standard dryer style flapper.
I have an extended exhaust run and had difficulty tracking down the source of odor. After trying for a week I eventually got fed up and sealed every joint/seam with clear silicone. Nailed it wherever it was.
Properly functioning exhaust with no restriction there is no odor. The only thing I can think of is the hose connections.
Ok, I am off to Home Depot as soon as they open. I already have the foil tape, but I want to get some weatherstripping to seal the area around that window vent.
Also - anyone have a suggestion to secure this window? It’s not latched anymore, obviously, since I inserted that window vent. But I would like to at least make it slightly less easy for burglars.
You could cut a brace of wood to place between the top edge of the open section and the top of the window preventing it from opening any further.
Depending on where you live condensation, energy efficiency, or black widows may have to be a consideration in sealing the duct when not in use:
https://community.glowforge.com/t/my-glowforge-is-full-of-water-condensation/9876?source_topic_id=14784I am in Western Washington (near Seattle). Temperatures are generally mild due to the proximity to the ocean, so I guess I will see. I don’t want condensation, but OTOH I don’t want lung cancer.
I also have the screw clamp at the machine tight. I used a nut driver instead of a screwdriver to cinch it down. I don’t doubt it’s possible to break the flange, but the structure of a circle can withstand considerable pressure applied evenly around it’s circumference as those screw clamps do.
I was just going to mention that the Quick Disconnect that we use was not designed to be air tight, and that might be the source of your leaks. We got around it with copious application of clear silicone caulk. 
I have foil tape around the pipe side of the quick disconnect, so I am pretty sure that’s not leaking. But I don’t see how I could caulk the disconnect mechanism without eliminating it’s ability to disconnect (quickly). I think I will just remove that part from the equation.
While there may be some smell from time to time, I never experience a sharp odor unless there is some leak or the exhaust is somewhat obstructed. Double check the length of the hose, all connections, eliminate all hose leaks and also ensure that the final exhaust has nothing that would restrict it, like a fine mesh screen or something.
It’s hard to describe without taking it apart - just check the connections, there might be places where it needs caulking.
Here’s a really lousy picture, but you can see some of the places where we caulked on the inside through the acrylic panel.
Thanks, Jules. That looks like a MUCH better quick-disconnect. The one I am using is really flimsy, and I am sure is not sealing well. Where did you get that one?
My quick-disconnect likes to leak too. One other question: what’s the prevailing wind direction? If you’re trying to exhaust into the wind you can have problems. Oh, and how’s the seal around the panel that’s blocking the window?
It’s actually two parts - one is the end cap flap things, and the other is a two-part Quick Disconnect, which makes it possible to caulk the pieces where they are permanently attached to the hose and flap cap.
I think we got that at Lowe’s. (Might have been Home Depot though, they both should carry similar products in the dryer hose connection section.)