The effect of various chemical additives e.g., brominated phenyl ether, chlorinated paraffin wax, inorganic oxides and halogenated rubbers on the flame retardancy and impermeability of brominated butyl rubber (BIIR) has been described, Chloroprene rubber (CR) in combination with chlorinated paraffin wax, halogenated phenyl ether and chlorinated polyethylene elastomer was found to offer best match of restricted flammability, thermal stability, physico-mechanical properties and vapour impermeability.