The ornamental design for an airtransferdevice, as shown and described.
FIG. 1 is a front view of an air transfer device showing my new design.
FIG. 2 is a right-side elevation view of FIG. 1.
FIG. 3 is a top view of FIG. 1.
FIG. 4 is a bottom view of FIG. 1.
FIG. 5 is a left-side elevation view of FIG. 1.
FIG. 6 is a back view of FIG. 1; and,
FIG. 7 is a frontal perspective view of the air transfer device.
The broken lines in the drawings views are included for the purpose of illustrating portions of bthe air transfer device that form no part of the claimed design.