Patent ID: 8679415

Claim:
A mat for use as a mounting mat or end cone insulation in an exhaust gas treatment device having a gas inlet end and a gas outlet end, the mat comprising a sheet of inorganic fibers having opposite first and second major surfaces, a length, a width and an uncompressed thickness; wherein the sheet comprises a first portion having a first uncompressed basis weight and a second portion having a second uncompressed basis weight that is greater than the first basis weight; wherein the sheet comprises a base sheet having a substantially uniform basis weight and a separate piece of sheet material joined to at least one of the first and second major surfaces of the base sheet; wherein at least one of the base sheet or the separate piece of sheet material is intumescent; and wherein the separate piece of sheet material is joined to the base sheet such that, when the sheet is installed in the exhaust gas treatment device, the sheet is positioned in the exhaust gas treatment device such that the separate piece of sheet material is proximate to the gas inlet end of the exhaust gas treatment device.