46 CFR § 197.330 - PVHO - Closed bells.
(a) Except as provided in paragraph (b) of this section, each closed bell must meet the requirements of § 197.328 and -
(1) Have underwater breathing apparatus for each occupant stored inside each separately pressurized compartment;
(2) Have an umbilical;
(3) Have lifting equipment attached to the closed bell capable of returning the occupied closed bell when fully flooded to the dive location;
(4) Be capable of recompressing on the surface to the maximum design diving depth;
(5) Be constructed and equipped as required by § 197.332;
(6) Have an emergency locating device designed to assist personnel on the surface in acquiring and maintaining contact with the submerged PVHO if the umbilical to the surface is severed;
(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 -
(i) Twelve hours after an accident severing the umbilical to the surface when the umbilical to the surface is the only installed means of retrieving the closed bell; or
(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.
(b) A closed bell that does not meet the requirements of paragraphs (a)(3), (a)(4), and (a)(5) of this section, must be capable of attachment to another PVHO that -
(1) Allows the transfer of personnel and diver's equipment under pressure from the closed bell to the PVHO;
(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
(4) Allows the transfer of personnel and diver's equipment under pressure from the PVHO to the decompression chamber.