dust from vent

I have an 88 Oldsmobile in so-so shape. Today when I turned it on, dust started to fly from the vents (where the heat or air condition usually comes out). There was no smoke - only dust, and there are no warning lights. Even if the heat is turned off, dusty air still comes out of the vents. What could be the problem? I am a student and don't have much money to take it to a mechanic (I just spent a few hundred fixing the brakes). Please help me.

I don't know about your Olds specifically but most cars get fresh air from the lower part of the windshield/hood area. This is a great place for leaves and other stuff to gather. It could also be some of the duct/filter material deteriorating in the vent system.

Thanks for the reply. My car was burried under lots of snow for several days. Is it easy to clean the lower part of the windshield area? Should I just turn the car on and let the stuff flush out?

On mine, I had to remove plastic trim(screwed down) which allowed me to reach in with my hand to remove the big pieces and then I used my shop vac to clean out the rest.

I'll try to do that. Thank you for all your help.