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Duct Insulation

Asbestos in Duct Insulation and Other Building Materials

Before the early 1980s, asbestos duct insulation was extremely common. Because it was used so extensively in the HVAC and ventilation systems of homes, buildings and large marine vessels, it is likely that much of this material still remains in service.

There were three types of asbestos used for duct insulation materials during most of the 20th Century. Most of this consisted of "white" asbestos. Also known as chrysotile, this product is found in a type of metamorphic rock known as serpentine. The largest producer of chrysotile in the U.S. before 1990 was W.R. Grace, which used the substance not only in its own products, but supplied many other firms with raw asbestos as well.

One common duct insulation material manufactured and marketed by the W.R. Grace Corporation was Monokote. This product is still sold, and today is gypsum-based. As late as 2007 however, the product still contained up to 1% asbestos fiber; prior to the 1980s, the amount of asbestos in this product was 5% or more. During the construction of the World Trade Center in the late 1960s, late asbestos disease specialist Dr. Irving Selikoff recalled seeing large amounts of this asbestos insulation falling from the construction site "like snow."

Duct Insulation Products Containing Asbestos

The following partial list of duct insulation products were known to contain asbestos:

Product Name Start Year End Year
Celotex Carey Insulation Duct

Hazards Associated with Duct Insulation Products

HVAC building and maintenance workers suffer some of the highest rates of asbestos diseases, largely as a result of exposure to duct insulation products. Demolition workers laboring on buildings where Monokote or other similar products were installed are also at risk, as tearing down structures containing old and worn asbestos can release clouds of asbestos dust into the air. Asbestos exposure is strongly linked to the development of malignant mesothelioma.



Bowker, Michael. Fatal Deception: The Untold Story of Asbestos (New York: Touchstone, 2003)

N/A. "Asbestos Linked to Autoimmune Diseases." Environmental Health Perspectives, vol. 113 (2004)

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