Patent ID: 8225553

Claim:
A fumetight gasket for use in a doorway, the gasket comprising: an elongated member having a substantially D-shaped cross-section mountable to a substantially U-shaped gasket retainer of a door frame, the elongated member having: a substantially D-shaped outer core comprising silicone rubber; and an inner core within the substantially D-shaped outer core, the inner core comprising an intumescent material having an expansivity that allows the intumescent material to expand and exit the inner core of intumescent material to fill doorway voids left by the deterioration of the outer core during fires, when the inner core is exposed by the deterioration of the outer core, wherein the inner core of intumescent material is located at a substantially central portion within the D-shaped outer core, the inner core of intumescent material having a circular cross section, and wherein the front side is a curved side, the curved side being formed substantially symmetrical with the circular inner core section, wherein the substantially D-shaped outer core comprises: a flat back side for contacting a back wall of the substantially U-shaped gasket retainer; two side portions for contacting side walls of the substantially U-shaped gasket retainer; and a front side protruding to make contact with a door panel under pre-fire conditions when the door panel is in a closed position, and wherein the ratio of a diameter of the inner core of intumescent material, to a length of the flat back side is about 2:3, and the ratio of the diameter of the inner core of intumescent material, to a height from the flat back side to the top of the front side is about 2:3.