I really don't know how to explain my question, but here is a shot. The filters on my heat-AC are metal and washable. With the size of the holes in them I don't see how they can do much filtering. It takes months before they even show any traces of dirt. I would like to replace them with something with more filtration, because we can dust and the next day its back, plus allergies. The slots that the filters slide into are only about ¼" wide so I can't find anything that will fit. Can I just add filters over the top of them? Will it damage my fan, ETC.?