Dear Glenn: I have noticed a lot of "soot" along the edges of my carpets and on the walls. Is this the sign of a dirty furnace?

-- Molly, Trenton

Dear Molly: The black lines are not signs of a dirty furnace but of negative air. Your house is expelling more air than is being replenished naturally through windows and doors. This causes a pressure imbalance that is pulling air through tiny cracks in the walls. The air carries a good deal of dust, which is "filtered" through the carpeting, depositing the line of dirt you see along the wall. One solution to the problem would be an EQUALIZ-AIR air makeup unit by Xavier, (734) 462-1033, www.equaliz-air.com. They are carried by Damman Hardware and www.wattbusters.com.