Section 197.328 - PVHO-General(a) Each PVHO, contracted for or purchased after February 1, 1979, must be built and stamped in accordance with ASME PVHO-1.(b) Each PVHO, contracted for or constructed before February 1, 1979, and not Coast Guard approved, must be submitted to the Coast Guard for approval prior to February 1, 1984.(c) To be approved under paragraph (b), a PVHO must be-(1) Constructed in accordance with part 54 of this chapter; or-(2) Be built in accordance with section VIII, division 1 or division 2 of the ASME Code; and- (i) Have the plans approved in accordance with § 54.01-18 of this chapter;(ii) Pass the radiographic and other survey tests of welded joints required by section VIII, division 1 or division 2, as appropriate, of the ASME Code; and(iii) Pass- (A) The hydrostatic test described in § 54.10-10 of this chapter; or(B) The pneumatic test described in § 54.10-15 of this chapter and such additional tests as the Officer-in-Charge, Marine Inspection (OCMI) may require.(d) Each PVHO must- (1) Have a shut-off valve located within 1 foot of the pressure boundary on all piping penetrating the pressure boundary;(2) Have a check valve located within 1 foot of the pressure boundary on all piping exclusively carrying fluids into the PVHO;(3) Have the pressure relief device required by ASME PVHO-1;(4) Have a built-in breathing system with at least one mask per occupant stored inside each separately pressurized compartment;(5) Have a two-way voice communications system allowing communications between an occupant in one pressurized compartment of the PVHO and-(i) The diving supervisor at the dive location;(ii) Any divers being supported from the same PVHO; and(iii) Occupants of other separately pressurized compartments of the same PVHO;(6) If designed to mechanically couple to another PVHO, have a two-way communications system allowing communications between occupants of each PVHO when mechanically coupled;(7) Have a pressure gage in the interior of each compartment that is-(i) Designed for human occupancy; and(ii) Capable of having the compartment pressure controlled from inside the PVHO;(8) Have viewports that allow observation of occupants from the outside;(9) Have viewports that meet the requirements of ASME PVHO-1 except those PVHO's approved under paragraph (b) of this section which have nonacrylic viewports;(10) Have means of illumination sufficient to allow an occupant to-(ii) Operate the installed systems within each compartment;(11) Be designed and equipped to minimize sources of combustible materials and ignition;(12) Have a protective device on the inlet side of PVHO exhaust lines;(13) Have a means of extinguishing a fire in the interior;(14) Have a means of maintaining the oxygen content of the interior atmosphere below 25 percent surface equivalent by volume when pressurized with air as the breathing mixture;(15) Have a means of maintaining the interior atmosphere below 2 percent surface equivalent carbon dioxide by volume;(16) Have a means of overriding and controlling from the exterior all interior breathing and pressure supply controls;(17) Have a speech unscrambler when used with mixed-gas;(18) Have interior electrical systems that are designed for the environment in which they will operate to minimize the risk of fire, electrical shock to personnel, and galvanic action of the PVHO; and(19) Be tested after every repair, modification, or alteration to the pressure boundaries as required by § 197.462 .