Dependable and Easy-to-Use Firestop Sealant. Tough and ready-to-use, 3M Fire Barrier Sealant CP 25WB+ is a high-performance, one-component, latex-based, intumescent sealant that dries to form a monolithic firestop seal. This sealant also acts as a barrier to airborne sound transmission. As penetrants are exposed to fire, the unique intumescent property of this material allows 3M Fire Barrier Sealant CP 25WB+ to expand and help maintain a firestop penetration seal for up to 4 hours. This sealant is designed to help control the spread of fire, smoke and noxious gases before, during and after exposure to a fire when installed in accordance with a listed through-penetration or fire-resistive joint assembly system (STC-Rating of 54 when tested in a STC 54-rated wall assembly). Recommended Applications: HVAC ducts and vents; Metallic and non-metallic pipes; Blank openings; Single and bundled cables; Insulated pipe; Pipe and cable through-penetrations; Busways; Combos; Rated wall, floor and floor-ceiling assemblies; Static construction joints. Ready to Protect for Consistent Results - 3M Fire Barrier Sealant CP 25WB+ firestops blank openings and penetrations passing through fire-rated floor, floor/ceiling or wall assemblies and other fire-rated interior building construction. This halogen-free sealant is capable of expanding a minimum of 3 times its dried volume when exposed to temperatures above 1000°F (538°C). We engineered this sag-resistant sealant to exhibit strong adhesion to a full range of construction substrates and penetrants. Applied with conventional caulking equipment, this gun-grade sealant offers an excellent caulk rate, no mixing is required. In addition, this water-based sealant is paintable as well as re-enterable and repairable, offering easy application and clean-up. Reliable and Affordable Fire Protection Effective and easy to install.