The ornamental design for a firedetector, as shown and described.
FIG. 1 is a front perspective view of the proposed design.
FIG. 2 is a front elevation view of FIG. 1.
FIG. 3 is a left side elevation view of FIG. 1.
FIG. 4 is a right side elevation view of FIG. 1.
FIG. 5 is a top plan view of FIG. 1.
FIG. 6 is a back elevation view of FIG. 1; and,
FIG. 7 is a bottom plan view of FIG. 1.
The broken line showing of elements, openings and the bottom of the design is included for the purpose of illustrating portions of the “article” and forms no part of the claimed design.