So I have read in numerous threads that my 2000 Dodge Durango 5.9L R/T does not have a cabin air filter. However, when my air conditioning is on, occasionally black spongey material similar to that of an air filter comes through my vents. What or Where could this material be coming from? Thank you.

 

Could be your flapper door deteriorating . I could not find a pic, but when I replaced my heater core and ac evap the material looked a lot like what you are describing.

 

It could also be the foam around the vents. I have already replaced all the foam around mine because it so deteriorated.

 

there is no cabin air filter.. its most likely what was said above.