BOSS 136 Fireblock/Draftstop Sealant is a single component fire rated sealant and is a non combustible filler caulking used for fireblocking applications in the annular space around wires, pipes, ducts, vents, cable lines and other penetrations to the building envelope. It is a non-slumping sealant that sets to form a hard surface. BOSS 136 can be applied to any gap or penetration where the specification is noncombustible and/or ASTM-E136 rated. BOSS 136 is to be used for interior applications only. BOSS 136 is colored red for ease of inspection. Std Cartridge.