The ornamental design for a combination gas pressurereliefvalve and safety whistle, as shown and described.
FIG. 1 is a perspective view of a combination gas pressure relief valve and safety whistle showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a left side view thereof, the right side view being a mirror image of FIG. 3;
FIG. 4 is a back view thereof;
FIG. 5 is a top view thereof; and,
FIG. 6 is a bottom view thereof.
The broken lines shown in the figures are for the purpose of illustrating portions of the combination gas pressure relief valve and safety whistle and form no part of the claimed design.