Duct Sealants Duct sealant STC duct sealant is specially formulated for HVAC systems, air ducts, and ventilation applications. Ductwork sealant STC duct sealant is specially formulated for HVAC systems, air ducts, and ventilation applications. Palduct sealant PAL duct sealant is a weatherproof grade sealant specially formulated for HVAC systems, air ducts, and ventilation applications
