Spotless HVAC filter
Why would my HVAC filter show absolutely no dirt or dust? It fits tightly and there is no residual dust in the air handler unit. A couple of years ago I found that the top of one of the return runs was never closed in, leaving it open to the mechanical room in which that return was located. I covered the opening with duct board and sealed it with mesh and mastic. The majority of returns are panned (what a joke!) and are not accessable. Those that are accessable, I have also sealed appropriately. The filter may not display dust, but the house sure does! Climate Zone 5.