Asbestos in Heating Ducts and Other Building Materials
Asbestos was used in a number of different applications in heating ducts. A type of asbestos cloth was commonly used to cover air handler vibration dampers. Asbestos insulation was often wrapped directly around the outside of the ducts to insulate them and make the more efficient at carrying hot or cool air through a building. Transite cement, a form of cement made with asbestos fibers, was commonly used for flues, pipes, and in the ducts themselves.
Hazards Associated with Heating Duct Products
The most common type of asbestos used for fireproofing and the protection of heating ducts is a variety known as chrysotile. White in color and relatively soft, chrysotile fibers are extracted from a type of metamorphic rock known as serpentine. Due to their molecular structure, chrysotile fibers tend to curl up (hence the name "serpentine"). The most common disease caused by exposure to this type of asbestos is known as asbestosis. This condition occurs when the fibers are inhaled and cause abrasions on the internal surfaces of the lung. This in turn results in a build-up of scar tissue, which over time reduces the ability of the lungs to take in oxygen. Other conditions that result from exposure to asbestos include the formation of pleural plaques, which is a hardening of lung tissue as well as mesothelioma, a form of cancer.
Heating ducts and HVAC systems pose a particular threat to building maintenance workers. Insulation in older buildings constructed prior to 1980 that have not undergone significant renovation may still have asbestos insulation and other materials in them. As these materials age, they become friable, meaning that they become fragile and capable of releasing fibers into the environment. Once they are airborne, these fibers can easily be inhaled by those working in the area.Sources
Bowker, Michael. Fatal Deception: The Untold Story of Asbestos (New York: Touchstone, 2003)
InspectAPedia. “ASBESTOS HVAC DUCTS - A Guide to Identification of Asbestos Materials On or In Heating and Cooling Duct Work.” (http://www.inspectapedia.com/aircond/DuctAsbestos.htm). Retrieved 6 January 2011.