I notice that during this cold winter at Edmonton that my gas furnace filters contain a larger amount of a whitish colored ash on the cold air return side of the filter. I would like to know where this ash is coming from. The air quality in the house seems fine so I cannot see how the ash is coming from the cold air returns. Could the ash indicate a leak in the heat exchanger?
My gas furnaces are mid efficiency ICG Ultimate II (17 years old)
Regards,
Michael Brady