Patent ID: 7428903

Claim:
A filtering face mask that comprises: (a) a mask body that is adapted to fit over the nose and mouth of a wearer, that is fluid permeable to air, and that comprises filter media; and (b) an exhalation valve that is positioned on the mask body substantially opposite to a wearer's mouth when the mask is being worn, the exhalation valve comprising: (1) a valve seat that comprises: (i) a seal ridge that terminates at a seal surface; and (ii) an orifice that comprises a plurality of openings separated by cross members and that is circumscribed by the seal ridge and the seal surface; and (iii) a flap-retaining surface; (2) a single flexible flap that has a generally uniform thickness and that is held in an abutting relationship to the flap-retaining surface to create a non-centrally disposed stationary portion and only one free portion of the flap, the flexible flap also having a peripheral edge that includes only one stationary segment and only one free segment, the stationary segment of the peripheral edge being associated with the non-centrally disposed stationary portion of the flap so as to remain at rest during an exhalation, and the only one free segment being associated with the only one free portion of the flexible flap so as to be lifted away from the seal surface during an exhalation, the only one free portion also being located below the non-centrally disposed stationary portion when the filtering face mask is worn on a person, wherein the flexible flap would normally assume a flat configuration when not secured in the valve seat and having no forces applied to it but when secure to the valve seat and viewed without a fluid passing through the orifice, the flexible flap (i) has a curved profile over the orifice area when viewed from a side elevation in its closed position on the valve seat and (ii) is pressed towards the seal surface in an abutting relationship therewith under any orientation of the mask body; and (3) a valve cover that has a ceiling that is distanced further from the valve seat proximate the free segment of the peripheral edge of the flexible flap than proximate the stationary segment of the peripheral edge, the valve cover further including a surface that holds the flexible flap in the abutting relationship against the flap-retaining surface.