This is not about the filter for the heating apparatus, but the refrigerator: ours was thick with dust and dirt on its backside. Friges are hard to pull out so no one bothers to clean the drip pan or the grills. Ours had 20 years of accumulated grime and it was so gross to clean! A big yuckkk of a job. I think Beach Runner hit the nail on the head. No one takes care of property, no matter how much you pay them, as much as the owner. You have to be on top of things all the time or they'll go to pot.