a fireproof , compressible , intumescent , elastomeric material useful to seal expansion joints , curtain wall gaps and penetrations in floors and walls in order to prevent the passage of flame and smoke . a seal of the material retains strength before and after exposure to fire and provides superior resistance to the impact , erosion , and cooling effects of a hose stream used to combat a fire . the composition of this compressible , fireproof material consists of elastomers , vulcanizing agents , fillers , softening agents , and an intumescent . this fireproof material may be in cellular or noncellular form with various degrees of compressibility and softness . it can be produced in sheets , molded parts , and continuous length strips . it may be vulcanized or nonvulcanized .