The ornamental design for a humidifier, as shown and described.
FIG. 1 is a perspective view of a humidifier showing the design;
FIG. 2 is a front side elevation view thereof;
FIG. 3 is a rear side elevation view thereof;
FIG. 4 is a left side elevation view thereof;
FIG. 5 is a right side elevation view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof;
FIG. 8 is a cross sectional view taken in the direction of line 8-8 in FIG. 6; and,
FIG. 9 is an enlarged detail view of area 9 circumscribed within FIG. 8.
The evenly spaced broken lines in FIGS. 8 and 9 depict the boundaries of the detail area and the detail drawing and form no part of the claimed design.
The oblique shading lines in the drawings are included to denote the transparent or translucent quality of surface planes of the humidifier.