Soot in house from oil furnace?
I cleaned the windows when we moved in 8 months ago and it came off jet black. After that, we had our oil furnace cleaned and he said it was VERY dirty but otherwise in good shape. I just cleaned the windows again and I am getting jet black again, not as much, but a significant amount. I can't imagine where this could be coming from except the heat. Does anyone know what could be causing this and how to stop it?