Abstract: A flexible barrier for preventing the spread of fire through areas of a building includes a layer of inorganic fibrous material sandwiched between two panels of material having sufficiently high thermal conductivity to diffuse and dissipate heat without burning when exposed to a flame. The panels and blanket are joined together with a filament having sufficiently high tensile strength and resistance to heat to maintain the panels and layers in laminar relation. Plural barrier sections may be attached together with the filament at a factory or at the installation The laminar panel and blanket combination is lightweight, easily cut and installed, and advantageously retards the passage of heat when placed across an opening.