Air tank

FIG. 1 is a top, front perspective view of an air tank;

FIG. 2 is a front view thereof;

FIG. 3 is a back view thereof;

FIG. 4 is a left-side view thereof;

FIG. 5 is a right-side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The dashed broken lines depict portions of the air tank that form no part of the claimed design. The dot dashed broken lines represent symbolic break lines. The dot dashed break lines and any portion of the air tank between the break lines forms no part of the claimed design.