FIG. 1 is a front view showing the ornamental design of a first embodiment of an air heater according to the present invention;
FIG. 2 is a top view of the air heater of FIG. 1;
FIG. 3 is a bottom view of the air heater of FIG. 1;
FIG. 4 is a back view of the air heater of FIG. 1;
FIG. 5 is a perspective view of the air heater of FIG. 1;
FIG. 6 is a reverse perspective view of the air heater of FIG. 1;
FIG. 7 is a front view showing the ornamental design of a second embodiment of an air heater according to the present invention;
FIG. 8 is a top view of the air heater of FIG. 7;
FIG. 9 is a bottom view of the air heater of FIG. 7;
FIG. 10 is a back view of the air heater of FIG. 7;
FIG. 11 is a perspective view of the air heater of FIG. 7;
FIG. 12 is a reverse perspective view of the air heater of FIG. 7;
FIG. 13 is a front view showing the ornamental design of a third embodiment of an air heater according to the present invention;
FIG. 14 is a top view of the air heater of FIG. 13;
FIG. 15 is a bottom view of the air heater of FIG. 13;
FIG. 16 is a back view of the air heater of FIG. 13;
FIG. 17 is a perspective view of the air heater of FIG. 13; and,
FIG. 18 is a reverse perspective view of the air heater of FIG. 13.