At least semiannually and after any system activation, maintenance shall be conducted with the manufacturers design, installation and maintenance manual.
Fixed temperature-sensing elements of the fusible metal alloy type shall be replaced at least semiannually from the date of installation or more frequent, if necessary, and shall be destroyed when removed.
The year of Manufacture and the date of installation of fixed temperature sensing elements shall be marked on the system inspection tag, and the tag shall be signed or initialed by the installer.
The following parts of wet chemical extinguisher systems shall be subjected to a hydrostatic pressure test at intervals not to exceed 12 years: