Abstract: A fire block sheet is provided comprising a laminate of (a) at least one rigid support layer comprising a cured glas fiber sheet impregnated with fire retardant epoxy resin and (b) an elastomeric cured silicone foam rubber layer containing alumina trihydrate secured to said support layer, said fire block sheet being capable, in a thickness of 1/16 inches, of withstanding flame penetration and preventing backside ignition when exposed at one side to a flame at a temperature of 1000.degree. C. for a period of at least 15 minutes. In a preferred embodiment, the elastomeric cured silicone rubber layer is sandwiched between two rigid support layers.

Abstract: A thermally insulative fire block sheet having an elastomeric layer is provided which has a surface flammability flame spread index of zero at 20 minutes of exposure in accordance with ASTM E-162 and which is capable, in a thickness of 1/16 inch, of blocking a flame of 1900.degree. F. for more than an hour. The sheet comprises at least two layers. One layer, facing the direction of the expected flame, is a silicone foam rubber comprising the reaction product of a vinylterminated polysiloxane containing --Si(CH.sub.3).sub.2 O-- units and an organohydrogensiloxane polymer containing Si(H)(CH.sub.3)O-- units. The silicone foam rubber also contains alumina trihydrate. The other layer is an adherent flame resistant support layer for said foam, preferably a glass cloth layer.

Abstract: A length of longitudinally extending duct assembly for heated corrosive gases includes an outer support duct and a substantially gas-tight liner. The liner is spaced from the outer support duct by a relatively yielding spacer material that accommodates expansion of the liner in directions parallel to the inner surface of the outer support duct and in directions normal to the inner surface of the outer support duct without imposing any substantial resistance to such thermal expansion.

Abstract: A length of longitudinally extending duct assembly for heated corrosive gases includes an outer support duct and a substantially gas-tight liner. The liner is spaced from the outer support duct by a relatively yielding spacer material that accommodates expansion of the liner in directions parallel to the inner surface of the outer support duct and in directions normal to the inner surface of the outer support duct without imposing any substantial resistance to such thermal expansion.