This has been happening to me as well. Im noticing it more right now and we just started using the heat again last week, so that sounds consistent. I only have electric, so that rules that out. What the Repairguy said sort of makes sense; If a coil or whatever is getting dusty/rusty during the humid summer and the it gets used again and gets very hot with the air blowing out our vents....
Im not very concerned about the health impacts, because the flakes seem to be too big to breathe in (as far as we can see). Im just sick of picking them up. Its less gross now that I know what it probably is. Thank you for posting.

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