312.50. Lines: Each line of the breathing mixture or oxygen supply system must
(1) be designed for its intended use and clearly identified to the diver supplied;
(2) include an easy-to-reach shockproof supply valve; and
(3) be equipped with a pressure gauge, downstream from the supply valve, indicating the supply pressure of the breathing mixture or oxygen, with a dial and numbers easily readable by the diver’s tender.
The use of flexible hoses in an oxygen supply line is prohibited, except if the high speed flow of the oxygen in the flexible hose does not create a differential pressure greater than 700 kPa from one end of the hose to the other.
The use of quick-opening valves in an oxygen supply line is also prohibited, except if emergency stop valves are located at the point where the line goes through the hull of a hyperbaric chamber.
For the purposes of this section, “lines” means the rigid and flexible hoses and fittings of the breathing mixture or oxygen supply and distribution system.