Cal. Code Regs. tit. 8, § 5507 – Equipment Assembly and Installation.

(a) Equipment making up a bulk oxygen system shall be cleaned in order to remove oil, grease or other readily oxidizable materials before placing the system in service.
(b) Joints in piping and tubing may be made by welding or by use of flanged, threaded, slip or compression fittings. Gaskets or thread sealants shall be suitable for oxygen service.
(c) Valves, gages, regulators and other accessories shall be suitable for oxygen service.
(d) Installation of bulk oxygen systems shall be supervised by personnel familiar with proper practices with reference to their construction and use.
(e) After installation all field erected piping shall be tested and proved gas tight at maximum operating pressure. Any medium used for testing shall be inert and oil free.
(f) Storage containers, piping, valves, regulating equipment, and other accessories shall be protected against physical damage and against tampering.
(g) Any enclosure containing oxygen control or operating equipment shall be adequately vented.
(h) The bulk oxygen storage location shall be permanently placarded to indicate: “OXYGEN--NO SMOKING--NO OPEN FLAMES,” or an equivalent warning.
Note: Bulk oxygen installations are not hazardous locations as defined and covered in the California Electrical Safety Orders.