Ready-to-use, gun-grade, one-component silicone elastomers. Both cure upon exposure to atmospheric humidity to form a flexible seal. 3M Fire Barrier Sealants firestop openings and penetrations through floor slabs, walls and other fire-rated building partitions and assemblies. 3M Fire Barrier Sealants, when installed properly will control the spread of fire before, during and after exposure to open flames.