We have oil hot-air heat. There was an issue of an oil smell, so I called our service company. They came out, said they needed to adjust an injector or ignitor and the problem seemed gone for a few days but then came back. Different guy came out, said the injector or ignitor (sorry, this was a while ago, forgot which) was bad and replaced it. Problem solved. No more smell. That was last winter. Furnace was off for the summer though we have A/C so air was blowing through the ducts all summer. Now, cold nights have us turning on the furnace. When it first comes on, some black ash comes out of the 2 ducts that are closest to the furnace (not all of them). It looks like black flakes but when you touch them they disintegrate basically - looks and smells like ash to me. It's maybe 5-10 flakes around the 2 ducts, and seems to stop as the furnace runs. (i.e. if I vacuum them up, no more appear).
Any idea what this is, and a guesstimate of the cost to fix/replace? Minor or major problem here..?