Until the 1980s, asbestos was included in the manufacturing process of duct adhesives due to its fire-resistant properties. Even though it was also found in spray-on form, the most known duct adhesive was the tape one. This type of adhesive was made with a foil backing and heat-resistant cement or compound containing asbestos fibers.
For the people working with heating ducts, the adhesives used on them posed a high risk of asbestos exposure if they were found in a friable state. This happened due to the passing of time and the constant high temperatures. You could have been exposed if: