Patent ID: 7117868

Claim:
A filtering face mask that comprises: (a) a mask body that is adapted to fit over the nose and mouth of a wearer; and (b) an exhalation valve that is attached to the mask body, the exhalation valve comprising: (1) a valve seat that comprises: (ii) a seal surface; and (ii) an orifice that is circumscribed by the seal surface; (2) a single flexible flap that has a fixed portion and a free portion and first and second opposing ends, the first end of the single flexible flap being associated with the fixed portion of the flap so as to remain at rest during an exhalation, and the second end being associated with the free portion of the flexible flap so as to be lifted away from the seal surface during an exhalation, the second end also being located below the first end when the filtering face mask is worn on a person, the flexible flap being positioned on the valve seat such that the flap is pressed towards the seal surface in an abutting relationship therewith, under any orientation of the valve, when no external forces from the movement of fluid are exerted upon the flap; and (3) a valve cover that is disposed over the valve seat and that comprises: (i) an opening that is disposed directly in the path of fluid flow when the free portion of the flexible flap is lifted from the seal surface during an exhalation; and (ii) a fluid impermeable ceiling that has an interior that has a means for preventing the free end of the flexible flap from adhering to the fluid-permeable ceiling when moisture is present on the ceiling or on the flexible flap.