Patent ID: 6843248

Claim:
A filtering face mask that comprises: (a) a mask body that is adapted to fit over the nose and mouth of a wearer, the mask body comprising a filtration layer through which inhaled air may pass before being inhaled by a wearer of the face mask; and (b) an exhalation valve that is attached to the mask body directly in front of where the wearer's mouth would be when the mask is worn, the exhalation valve allowing air exhaled by a wearer to pass from an interior of the mask body to its exterior without having to pass through the filtration layer, the exhalation valve comprising: (1) a valve seat that comprises: (i) a seal surface; and (ii) an orifice that is circumscribed by the seal surface, the orifice having a cross-sectional area greater than about 2 square centimeters; and (2) a single flexible flap that has only one stationary portion and only one free portion and a circumferential edge, the circumferential edge having a first segment that is associated with the only one stationary portion of the flap so as to remain at rest during an exhalation and having a second segment that is 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 second segment of the circumferential edge also being located below the first segment when the filtering face mask is worn on a person, the flexible flap being mounted to the valve seat such that the one free portion of the flap exhibits a curvature over the orifice area when viewed from the side in the closed position and is pressed towards the seal surface in an abutting relationship with it, under any orientation of the exhalation valve, when a fluid is not passing through the orifice.