46 C.F.R. § 179.330 – Watertight doors.

(a) Hinged watertight doors are not permitted in bulkheads required by § 179.210 or § 179.212 unless the vessel will not proceed more than 20 nautical miles from shore and:
1. (1) The door separates a machinery space from an accommodation space and, in the judgment of the cognizant OCMI, the door will be kept closed except when a person is passing through the door; or
2. (2) The Commandant determines that, due to the arrangements of the vessel, the door will be kept closed except when a person is passing through the door.
(b) A hinged watertight bulkhead door must be fitted with a quick action closing devise operable from both sides of the door and indicator lights at the operating station showing whether the door is open or closed.
(c) Sliding watertight doors must meet the requirements of part 170, subpart H in subchapter S of this chapter.
(d) No more than one watertight door may be fitted in a watertight bulkhead, and it must be located as high and as far inboard as practicable.