A filtering face mask that has a mask body and an exhalation valve. The mask body is adapted to fit over the nose and mouth of a wearer. The exhalation valve is attached to the mask body and includes a valve seat that comprises a seal surface, an orifice that is circumscribed by the seal surface, a flap-retaining surface, and 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 is associated with the fixed portion of the flap so as to remain at rest during an exhalation, and the second end is 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 is located below the first end when the filtering face mask is worn on a person. The flexible flap is positioned on the valve seat such that the flap is pressed towards the seal surface in an abutting relationship therewith when a fluid is not passing through the orifice. A valve cover is disposed over the valve seat and comprises a surface that mechanically holds the flexible flap against the flap-retaining surface.