That caught your attention, right?!
When my brother-in-law started asking me about his furnace problems of course one of the first things I asked him was: "Is your filter clean"? His response was that years ago he took his filter out because the air wasn't coming out like it used to. After a drug-out conversation at our family get-together I finally gave up and pulled his son aside and suggested he help his dad out, he's not thinking clearly. Oh, boy..... For Years he hasn't run his furnace with a filter.