Patent ID: 7028689

Claim:
A filtering face mask that comprises: (a) a 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) a valve seat that comprises a seal surface and an orifice through which exhaled air may pass to leave the interior gas space; and (ii) a flexible flap that is mounted to the valve seat such that the flap makes contact with the seal surface when the valve is in a 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, the flexible flap comprising at least first and second juxtaposed layers, wherein at least one of the first and second layers is stiffer than the other layer.