Q. My daughter was trying to sell her home, but when the buyer found out the house had asbestos on the furnace he decided to buy some other home. I have read that boilers have asbestos, but I never heard of asbestos on a furnace. Have you ever seen something like this?
A. Your question was short on details, but quick to the point. In some older homes, asbestos can be found on the joints of the furnace's ductwork, as a binder in floor tiles, in the glue below foor tiles, and as a binder for plaster. Asbestos is a known carcinogen when inhaled, so it is best never to disturb the materials.
The asbestos in floor tiles and the glue for floor tiles are in a solid form and are not easily disturbed. Asbestos fibers in plaster are also bound up in the plaster and become a concern if and when the plaster is damaged or disturbed. Asbestos used in the tape to seal ductwork is more fragile and can become airborne because of all the air movement in and around the ducts. This is often referred to as "friable asbestos" and should be removed only by a professional environmental contractor.
When the furnace fan is on, the return ducts will be under a negative pressure and air can be pulled into the ducts at the seams that are covered with asbestos tape. Some of the asbestos fiber will most likely be pulled into the ducts as well and distributed to the whole house.
The supply ducts that send air to the registers are under a positive pressure, which will blow asbestos fibers into the air at the joints and seams. If you look at the registers at the ends of the supply ducts, they may also be wrapped with the asbestos tape. Whether or not your daughter sells the home, she should have the asbestos professionally removed and the air in the home flushed through a HEPA (high-efficiency particulate air) filter to remove any lingering asbestos fibers.
• Dwight Barnett is a certified master inspector with the American Society of Home Inspectors. Write to him with home improvement questions at C. Dwight Barnett at d.Barnett@insightbb.com.
Scripps Howard News Service