Patent ID: 6874499

Claim:
A filter cartridge that comprises: (a) a housing that has at least one inlet and at least one outlet; and (b) a mass of filter material that is contained within the housing such that a fluid to be filtered passes through the at least one inlet, the filter material, and the at least one outlet; wherein the housing comprises a sheet material that has been thermo-formed around at least part of the mass of filter material to form at least a housing sidewall that assists in preventing passage of fluid between the filter material and the sheet material so that fluid passes through the filter material before exiting the housing, and wherein the housing includes attachment means for securing the cartridge to a face piece and the housing comprises a tray in which the mass of filter material is located, the tray having upstanding internal ribs on its base that engage and support the mass of filter material and define a space, forming an air chamber, between the base of the tray and the mass of filter material.