A filtering face mask that includes 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 an exhalation valve that is in fluid communication with the interior gas space. The exhalation valve includes a valve seat with a seal surface and an orifice through which exhaled air may pass to leave the interior gas space; and 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 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. The flap is unbiased when in its closed position and exhibits a cantilever bend ratio of 0.0050 or less.