The ornamental design for a gas phasefilter, as shown and described.
FIG. 1 is a top, front, and right side perspective view of a gas phase filter showing the new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side thereof;
FIG. 5 is a right side view thereof; and,
FIG. 6 is a top view thereof.
The evenly spaced broken lines depict portions of the gas phase filter that form no part of the claimed design. The dot dash dot broken lines denote the boundaries of the claim and form no part thereof.
The bottom view thereof is omitted since it does not contain ornamental features.