Defogger Controls problems of the 1996 Nissan Altima

Debris collects in the windshield well of my car. It then apparently falls down into the heating vent section. As a result, I have had smoke come out of the driver's side hood of my car, and a burning smell pour into the car cabin. I took the car to the dealer, who informed me that there was no filter on the car to prevent this from happening, and wants to charge me to fix the problem (by cleaning out debris). When I asked him how I prevent this from happening, he told me not to park under trees. This is virtually impossible to do where I live.