[Code of Federal Regulations] [Title 46, Volume 7] [Revised as of October 1, 2004] From the U.S. Government Printing Office via GPO Access [CITE: 46CFR197.322] [Page 427] TITLE 46--SHIPPING CHAPTER I--COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PART 197_GENERAL PROVISIONS--Table of Contents Subpart B_Commercial Diving Operations Sec. 197.322 Surface-supplied helmets and masks. (a) Each surface-supplied helmet or mask must have-- (1) A nonreturn valve at the attachment point between helmet or mask and umbilical that closes readily and positively; (2) An exhaust valve; and (3) A two-way voice communication system between the diver and the dive location or bell. (b) Each surface-supplied air helmet or mask must-- (1) Ventilate at least 4.5 ACFM at any depth at which it is operated; or (2) Be able to maintain the diver's inspired carbon dioxide partial pressure below 0.02 ATA when the diver is producing carbon dioxide at the rate of 1.6 standard liters per minute.