Section 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.