I claim the ornamental design for a respirator valve, as shown and described.
FIG. 1 is a front perspective view of a respirator valve showing my new design;
FIG. 2 is a rear perspective view thereof;
FIG. 3 is a top plan view thereof;
FIG. 4 is a bottom plan view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a left side view thereof;
FIG. 7 is a front elevation view thereof; and,
FIG. 8 is a rear elevation view thereof.
The ornamental design which is claimed is shown in solid lines in the drawings. The broken dot-dash lines define boundaries of the claimed design and form no part thereof. The broken lines in the drawings illustrate portions of the respirator valve that form no part of the claimed design.