Man it used to never bother me but today I am afraid of breathing dust, I inhaled larger quantities of it earlier this year and got sick as a dog! I had a fever, runny nose and a bad cough for like 2 weeks I felt rough (thou the first 2-3 days were the worst).
Come to find out, dust can kill you. Yes, literally, dead... Way I remember feeling, I don't doubt it anymore.
Mask? No way, if I even think I'm going to be around that stuff, I'm wearing either a respirator or a gas mask, funny as it may sound, after the way I got earlier this year, I don't take no chances with the dust anymore. If it's just a cloud here and there, I hold my breath.
Yeah, it does have to be a LOT of dust, if it's just some clouds, I can maneuver with it so I don't breathe it in, in between breaths.
National Geographic recently had an article about a farmer, now wears a thousand-dollar battery-powered full-cover respirator after some dust from barley made him sick, that stuff is rough I tell you.
Here's the thread I left about that (it got made fun of, but I am dead serious):
http://www.lawnsite.com/showthread.php?t=142668