I have really light carpet and I've had a terrible time with soot marks in this house.
They are around the room perimeter and under closet doors and even in the middle of the room over seams in the floor.
I was carpet shopping with my daughter and the sales person said
to call the HVAC guy and have them adjust how strong the air flow is from the vents
Are these soot marks caused by too much air flow from the vents?? Or did she just make this up?