Wherever there are seams or joints in ductwork or the sidewalls of the duct are pierced, the potential for air leakage exists. Besides contributing to energy waste, leaks can also create noise. Sealing of ductwork can be accomplished with the use of a viscous material which fills gaps and conforms to the surface without running. Duro Dyne DDS-181 is a UL181A-M and UL181B-M listed non-flammable water based duct sealant designed for sealing joints in low to high pressure systems. Specially formulated to be used indoors and outdoors.