Abstract: A uni-directional fluid valve particularly for use as an exhalation valve for a filter mask comprises a flexible flap attached at one end to a concave portion of a seat. The mounting of the flap imparts to it a transverse curvature, stiffening the flap sufficiently for it to remain seated in the absence of a pressure differential across it even when orientated with the seat above the flap.

Abstract: A filter mask has an eye shield comprising a sheet of flexible transparent material sealed to the mask along its lower edge. That edge of the eye shield material has one or more widthwise folds so that, while the upper edge of the mask can follow the contours over the nose and along the cheeks of a user the eye shield can adopt a more gentle curvature by relative compression of the folds where they pass over the nose and relative opening of the folds to each side. A comfortable fit can thereby be achieved without creasing of the eye shield and without detriment to the sealing of the mask against the user's face and the sealing of the eye shield to the mask.

Abstract: A uni-directional fluid valve particularly for use as an exhalation valve for a filter mask comprises a flexible flap attached at one end to a concave portion of a seat. The mounting of the flap imparts to it a transverse curvature, stiffening the flap sufficiently for it to remain seated in the absence of a pressure differential across it even when orientated with the seat above the flap.

Abstract: A uni-directional fluid valve particularly for use as an exhalation valve for a filter mask comprises a flexible flap attached at one end to a concave portion of a seat. The mounting of the flap imparts to it a transverse curvature, stiffening the flap sufficiently for it to remain seated in the absence of a pressure differential across it even when orientated with the seat above the flap.