Patent ID: 7188622

Claim:
A negative pressure filtering face mask that comprises: a) a mask body that is adapted to fit at least over the nose and mouth of a person to help define an interior gas space when worn; and b) a unidirectional exhalation valve that is secured to the mask body and that permits fluid communication between the interior gas space and an exterior gas space, the exhalation valve comprising: (i) a valve seat that comprises a resilient 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 flexible flap makes contact with the resilient seal surface when the valve is in its closed position and such that the flexible flap can move away from the seal surface in response to an exhalation to allow exhaled air to pass through the orifice to ultimately enter the exterior gas space.