46 CFR § 197.330 - PVHO - Closed bells.
(1) Have underwater breathing apparatus for each occupant stored inside each separately pressurized compartment;
(2) Have an umbilical;
(4) Be capable of recompressing on the surface to the maximum design diving depth;
(5) Be constructed and equipped as required by § 197.332;
(7) Have a capability to remove an injured diver from the water; and
(8) Have a life support capability for the intact closed bell and its occupants for -
(ii) A period of time, at least equal to 1 hour plus twice the time required to retrieve the bell from its designed operating depth and attach an auxiliary lifesupport system, after an accident severing the umbilical to the surface when the umbilical is one of the two independent installed means of retrieving the closed bell, each meeting the requirements of paragraph (a)(3) of this section.
(2) Meets the requirements of paragraph (a)(3) of this section;
(3) Is capable of attachment to a decompression chamber meeting the requirements of paragraphs (a)(4) and (a)(5) of this section; and