We formulated this fire sealant to dry and form a monolithic firestop seal that also acts as a barrier to airborne sound transmission. 3M? Fire Barrier Sealant CP 25WB+ is a red, one-component, gun-grade, latex-based, intumescent firestop sealant. This fire barrier sealant helps control the spread of fire, smoke and noxious gases before, during and after exposure to a fire.