3M's Fire Barrier Water Tight Silicone Sealants meet the new Underwriters Laboratories (UL) W Rating-Class One requirements for water tightness when used on horizontal floor penetrations. The sealants are used to firestop interior construction voids around blanks; metallic, non-metallic and insulated pipes; cable; cable trays; busways; HVAC ducts and combos in floor and wall penetrations. There are three sealants in the line, including the 3M Fire Barrier 1000 NS Silicone Sealant, a non-slumping silicone that has a UL firestop system rating for up to three hours; the 3M Fire Barrier 1003 SL Silicone Sealant, a self-leveling silicone that is rated for up to three hours; and the 3M Fire Barrier 3000 WT, an intumescent silicone that is rated for up to four hours. 3M. Circle 1.