The ornamental design for an ash pan, as shown and described.
FIG. 1 is a perspective view of an ash pan, showing my new design;
FIG. 2 is another perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a rear elevational view thereof;
FIG. 5 is a left side view thereof, the right side view being a mirror image of FIG. 5;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a partial enlarged view of FIG. 1.
The broken lines consisting of evenly spaced dash lines in the drawing depict portions of the ash pan that form no part of the claimed design; The broken lines encircling the enlarged detail views are for annotative purposes that form no part of the claimed design.