46 CFR §111.60-9

1. (a)General. A branch circuit that supplies equipment vital to the propulsion, control, or safety of the vessel must not supply any other equipment.
2. (b)Passenger vessels.
   1. (1)Each passenger vessel with firescreen bulkheads that form main fire zones must have distribution systems arranged so that fire in a main fire zone does not interfere with essential services in another main fire zone.
   2. (2)Main and emergency feeders passing through a main fire zone must be separated vertically and horizontally as much as practicable.