FIG. 1 is a perspective view of a portable air compressor from the left front showing our new design;

FIG. 2 is a perspective view from the left rear thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a right side elevational view thereof;

FIG. 5 is a left side elevational view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a rear elevational view thereof; and,

FIG. 8 is a front elevational view thereof.

The elements shown in dotted lines in FIGS. 1-5, 7 and 8 form no part of the claimed design.