U.S. Code of Federal Regulations
Regulations most recently checked for updates: Jan 20, 2020
(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.