FIG. 1 is a perspective view of the humidifier for use with a portable oxygen unit embodying the design of the present invention;

FIG. 2 is a front end elevational view thereof;

FIG. 3 is a rear end elevational view thereof;

FIG. 4 is a side elevational view thereof, the side opposite being a mirror image of the side shown in FIG. 4; and,

FIG. 5 is a top plan view thereof, the bottom view being a mirror image of the top view shown in FIG. 5.

The broken line showing of environmental structure in FIGS. 1, 4 and 5, is for illustrative purposes only and forms no part of the claimed design.