FST™ closed-cell duct sealant provides superior pressure-blocking power in the toughest environments. It stops methane and other gases to keep electrical systems intact. FST Duct Sealant is stronger, more chemically resistant, and cures 50 times faster than open-cell aerosol foams. The FST seal has excellent adhesion to PVC, rigid steel, EMT, IMC, fiberglass and polyethylene conduits.