Parashas Bamidbar · Passuk 3:31
Their duties comprised: the ark, the table, the lampstand, the altars, and the sacred utensils that were used with them, and the screendscreen I.e., the screening curtain; cf. 4.5.—all the service connected with these.
Chabad.org — English translation + Rashi
Source: Arachin 11a.
English: “And the altars” — it was taught: All the vessels that were in the Temple require immersion after the festival.
In context: Because the common people handled them during the pilgrimage gatherings, they need purification afterward.
Custom
Chazal teach that Temple vessels used by the public at the festivals require subsequent immersion.