The ornamental design for a firedetector, as shown and described.
FIG. 1 is a perspective view of the invention.
FIG. 2 is a front elevation view of FIG. 1.
FIG. 3 is a top plan view of FIG. 1.
FIG. 4 is a left side elevation view of FIG. 1.
FIG. 5 is a right side elevation view of FIG. 1.
FIG. 6 is a bottom plan view of FIG. 1; and,
FIG. 7 is a bottom plan view of FIG. 1.
No claim is made to the portions shown in shadow lines in the images. The bottom is unadorned and no claim is made to the bottom surface as the item is claimed as if on a surface.