What is that black stuff on the walls and registers?
The black “soot” on walls and registers is usually not a product of the machine running. Many factors cause these stains, including candles, especially scented, cooking with oils/grease, poor filter maintenance, and a variety of others. In addition, high velocity air from the registers causes air in the room to be pulled in toward the walls and registers. The dust particles suspended in the air collide against the wall and cause staining.
