(a) The piping between the cylinders and the appliances must be seamless annealed copper tubing or such other seamless tubing as may be approved by the Commandant.

(b) All high-pressure tubing between the cylinders and the regulators must have a minimum wall thickness of 0.049 inch. All low-pressure tubing between the regulator and appliances must have a minimum wall thickness of 0.032 inch.

(c) Tubing connecting fittings must be of the flare type; or connections may be soldered or brazed with material having a melting point in excess of 1,000 °F.