Red Devil offers a full line of duct sealants for professional HVAC contractors and DIYers. Red Devil’s versatile lines of duct sealants include D-Seal Water-Based Duct Sealant and F-Seal Water-Based 181 Duct Sealant, both offering superior adhesion for sealing metal and flexible ducts, vents, air conditioners and other interior and exterior HVAC appliances. Designed for use in conjunction with metal fasteners, Red Devil D-Seal is a smooth, water-based duct sealant suitable for all types of HVAC duct systems including metal ductwork, fiberglass, and duct board. Ideal for commercial HVAC applications, D-Seal is specially formulated for permanent flexibility and adhesion. It has excellent water-resistance and sealing strength, exceeding all SMACNA Pressure and Sealing Classes, and is UL 181A-M and B-M approved.