I have a fancy HEPA air filter in my GF room and two different air quality sensors that report PM2.5 and PM10 at being less than 8μg/m3 which is way less than the outdoor levels. The numbers barely go up when I am running the laser, so my venting is good. Yet, that room always has a low level smell of burnt wood. This isn’t a question of how to vent better or get rid of the smell. Its a question of what is the smell? Because I don’t think its PM2.5 or PM10 given my readings. Im curious about the chemistry behind the smell. What actually is it? What size is it?
When you burn anything on the laser, there is an ashy, sticky resin that will deposit on the grid, the inside of the machine and the material itself. (It’s why they put paper masking on both sides of the Proofgrade to capture most of the residue.)
Removing that masking immediately after lasering and popping it into a ziploc eliminates that small residual smell pretty promptly. When you get a buildup inside the machine, you can turn off the machine and clean things with a moist (not wet) wipe down of 50/50 vinegar and water. Cleaning occasionally prevents buildup and keeps the smells down.
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The chemical molecules related to smell are not particles any more than the smell of anything else. If you have an activated charcoal filter those chemicals can get bound to the carbon but the finest HEPA filter will not stop them. That is why the charcoal filter is usually after the HEPA filter.
You’ll notice it more if you open the lid soon after printing. Give it a little time to draw more out of the machine and you might notice a difference.
That said - I generally have no odor in my workshop, but if I leave the lid open, I notice some. Same can be said for the ginger/garlic dressing I had on the coleslaw I didn’t finish last night, and left the plate in the sink! 
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And Popcorn can be thick but only carbon filter can deal with it 
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