Why it is important to have a ventilation system! I was doing a little house cleaning in the workshop, (something I do frequently) and on this particular session I pulled the inlet vent off my paint booth's exhaust system. Guys & Gals this is what you are breathing in if you do not have an exhaust system in your modeling area.
I check and clean this duct work every month or so, the build up you're seeing isn't from a prolonged period of time. If you don't have a ventilation system, consider wearing a mask until you can install one. This stuff accumulates in your lungs.
I'm not trying to scare anyone, but please take reasonable precautions to protect yourselves. We like having you here.