Me’ila 25 - Kohanim Guarding The Temple (Tamid)
There were three places in the Temple where Kohanim stood honorary guard. These were chambers elevated above floor of the Temple, and one of them was called "The Hall of Fire." It was a dome, where large fires were burning throughout the night, because Kohanim had to perform their service barefoot and in only one layer of clothing. Young Kohanim were used for guarding: since they could not yet bring sacrifices, they could therefore afford to be up all night.
The Hall of Fire was a large structure, whose interior was encircled with ledges of stone. The heads of the group of Kohanim who were to serve the next day slept on these ledges. The ledges were not sanctified, which allowed sitting and sleeping on them, for otherwise sitting in the Temple is prohibited for everybody except for kings of the Davidian dynasty. Young Kohanim were not accorded this privilege, but slept each with his cushion on the ground. They would not sleep in their holy vestments, but would rather remove them, and fold them under their heads, and cover themselves with their personal garment.
If one of them experienced a seminal emission during the night, he would exit the Hall of Fire and proceed through an underground tunnel, where lamps were burning to illuminate his way, until he reached the Immersion Room, where he would immerse himself in a mikveh. A large fire was burning there for people to dry and warm themselves after immersion. There was also a "latrine of dignity," whose door was closed when someone was there, and thus one never had to speak in it.
Art: Charles Bargue - A Footman Sleeping