Patent ID: 8828129

Claim:
A two-stage air filter, comprising: an inlet side filter element, the inlet side filter element having an inlet surface, wherein the inlet side filter element is formed from a nonwoven glass fiber material; an outlet side filter element of nonwoven fiber material and having an outlet surface, the outlet side filter element having a finer gauge than the inlet side filter element, wherein the outlet side filter layer is formed of materials selected from the group consisting of polyester fibers and polyester/cotton fiber blends, the inlet side filter element and the outlet side filter element each having a mutually contiguous periphery and an adjacent filter element contact face forming a continuous, unbroken, homogeneous contact interface therebetween; a porous fabric sheet being disposed across the inlet surface of the inlet side filter element and being configured for positioning adjacent the mouth and nose of a user; a filter element retainer disposed across an exterior face of the porous sheet; and a frame disposed about the periphery of each of the filter elements, the filter element retainer and the porous sheet, the frame securing the filter elements together.