Where air pipes to ballast and other tanks extend above
the freeboard or superstructure decks, the exposed parts of the pipes
shall be of substantial construction; the height from the deck to
the point where water may have access below shall be at least 760
millimetres (30 inches) on the freeboard deck and 450 millimetres
(17½ inches) on the superstructure deck. Where these heights
may interfere with the working of the ship, a lower height may be
approved, provided the Administration is satisfied that the closing
arrangements and other circumstances justify a lower height. Satisfactory
means permanently attached, shall be provided for closing the openings
of the air pipes.