The ornamental design for a fire and/or smoke detector, as shown and described.
FIG. 1 is a top perspective view for a fire and/or smoke detector showing my new design;
FIG. 2 is a top view thereof;
FIG. 3 is a side view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a top view thereof; and,
FIG. 6 is a bottom view thereof.
The broken lines defining the central circular region, and the round circular regions seen at the top, bottom, and right side in FIG. 2 depict environmental subject matter that forms no part of the claimed design.