A filter cartridge, comprising: opposing cartridge outlet and cartridge inlet surfaces; an entry port for introducing air into the filter cartridge, the entry port being in fluid communication with at least one entry air space (1, 3, 5) formed in the filter cartridge; an exit port for directing filtered air out of the filter cartridge and, in use, into a respirator or other purified airspace, the exit port being in fluid communication with at least one exit air space (2, 4) formed in the filter cartridge; and a plurality of planar sorbent beds each having a constant depth of sorbent disposed in the filter cartridge between the entry port and the exit port for filtering air passing through the sorbent beds and the filter cartridge, said plurality of sorbent beds dividing an interior volume of the filter cartridge into said air spaces (1, 2, 3, 4, 5) which alternately fluidly communicate with said entry port and said exit port, each sorbent bed having a flat bed inlet surface adjacent to one entry air space (1, 3, 5) for airflow entry into the sorbent beds, and a flat bed outlet surface adjacent to one exit air space (2, 4) for airflow exit out of the sorbent beds; wherein the cartridge outlet surface is concavely curved to facilitate positioning of the filter cartridge, in use, adjacent a convexly curved interfacing surface of a user; and in that the sorbent beds are oriented with their bed inlet and bed outlet surfaces perpendicular to said cartridge outlet surface, each sorbent bed having an end which is adjacent to and which is shaped to conform to said concave curvature of the cartridge outlet surface. opposing cartridge outlet and cartridge inlet surfaces; an entry port for introducing air into the filter cartridge, the entry port being in fluid communication with at least one entry air space (1, 3, 5) formed in the filter cartridge; an exit port for directing filtered air out of the filter cartridge and, in use, into a respirator or other purified airspace, the exit port being in fluid communication with at least one exit air space (2, 4) formed in the filter cartridge; and a plurality of planar sorbent beds each having a constant depth of sorbent disposed in the filter cartridge between the entry port and the exit port for filtering air passing through the sorbent beds and the filter cartridge, said plurality of sorbent beds dividing an interior volume of the filter cartridge into said air spaces (1, 2, 3, 4, 5) which alternately fluidly communicate with said entry port and said exit port, each sorbent bed having a flat bed inlet surface adjacent to one entry air space (1, 3, 5) for airflow entry into the sorbent beds, and a flat bed outlet surface adjacent to one exit air space (2, 4) for airflow exit out of the sorbent beds; wherein the cartridge outlet surface is concavely curved to facilitate positioning of the filter cartridge, in use, adjacent a convexly curved interfacing surface of a user; and in that the sorbent beds are oriented with their bed inlet and bed outlet surfaces perpendicular to said cartridge outlet surface, each sorbent bed having an end which is adjacent to and which is shaped to conform to said concave curvature of the cartridge outlet surface.