Patent ID: 7645426

Claim:
A multilayer mat comprising: an intumescent layer having opposite outer edges, opposite ends, a first major surface and a second major surface opposite the first major surface, said intumescent layer having an area A 1 ; a first non-intumescent layer facing the first major surface of said intumescent layer, said first non-intumescent layer comprising inorganic fibers and said first non-intumescent layer having opposite outer edges, opposite ends, and an area A 2 that is greater than area A 1 , wherein said first non-intumescent layer has a major surface facing said intumescent layer with a first trough in said major surface, and wherein said intumescent layer is positioned in said first trough; and a second non-intumescent layer facing the second major surface of said intumescent layer, said second non-intumescent layer comprising inorganic fibers and said second non-intumescent layer having opposite outer edges, opposite ends, and an area A 3 that is greater than area A 1 , wherein said intumescent layer is sandwiched between said first and second non-intumescent layers and positioned entirely within the area A 2 of said first non-intumescent layer and the area A 3 of said second non-intumescent layer, with at least one of the outer edges of said mat being free of intumescent material.