Certified shaft alternative 1- and 2-hour fire-rated duct wrap. 3M Fire Barrier Duct Wrap 615 is a fire wrap certified for grease ducts to ASTM E 2336 (including ASTM E119 engulfment) in 2-layer systems. Certified for ventilation ducts to ISO 6944 in 1-layer systems and for other key life safety duct applications.