We claim the ornamental design for the dryer exhaust duct alarm, as shown.
FIG. 1 is an isometric view of a top view showing our design.
FIG. 2 is an isometric view of the underside of our design
FIG. 3 is a right side elevation view.
FIG. 4 is a left side elevation view.
FIG. 5 is a rear end elevation view.
FIG. 6 is a side elevation view;
FIG. 7 is side elevation view; and,
FIG. 8 is an end view of our design.
The dotted lines are an electronic housing shown for context as it may be placed in any position on the Figures and is not a part of the claimed Design.