Patent ID: 7503326

Claim:
A filtering face mask that comprises: (a) a filtering mask body that is adapted to fit at least over the nose and mouth of a wearer to create an interior gas space when worn; and (b) an exhalation valve that is in fluid communication with the interior gas space, the exhalation valve comprising: (i) valve seat that comprises a seal surface and an orifice through which exhaled air may pass to leave the interior gas space, wherein the seal surface exhibits a hardness of 0.05 Gpa or higher; and (ii) a monolayer flexible flap that is mounted to the valve seat such that a first major surface of the flap contacts the seal surface when the valve is in its closed position and such that the flap can flex away from the seal surface during an exhalation to allow exhaled air to pass through the orifice to ultimately enter an exterior gas space, wherein the flexible flap is unbiased when in the closed position, and wherein the flexible flap exhibits a cantilever bend ratio of 0.0050 or less.