Abstract: A two-way valve for use in breathing apparatus comprising a valve chamber having a supply end and a mask end, both ends having openings, a valve plate member of thin lightweight material freely movable within the valve chamber between the supply end and the mask end for closing respective openings, the valve plate member defining a flow axis and a generally circular opening centered on the flow axis, a plurality of support arms extending radially inwardly from the perimeter of the circular opening, the support arms defining and being joined together at a solid central hub, a plurality of stub members extending radially inwardly from the perimeter of the circular opening, a fastening boss extending from the central hub towards the mask end of the chamber, retaining flanges on the boss spaced from the valve plate, a flat planar flexible valve membrane attached to the valve plate member, the membrane having a central opening fitting elastically over the boss, and fitting between the valve plate member and the fl