Does the FAA require a specific grade of supplemental oxygen for part 91 operations? In a recent FAA knowledge exam, a question was asked whether medical grade or industrial grade oxygen can be substituted for the aviation grade supplemental oxygen for General Aviation, Part 91 flight. I have looked in the FAR/AIM for answers. But, there is not a specific regulation prohibiting the use of medical grade oxygen in aviation.
The FAA Safety Brochure OK-09-439 recommends that medical grade oxygen should not be used. Yet, there is a Civil Air Patrol document (another government entity that is regulated in part by the FAA) that refutes this due to changes in the understanding and delivery of supplemental medical grade oxygen.
Does anyone have a clear cut and recent regulation or document that clarifies this question? Please include links to the documentation.
Regulations don't usually include detailed technical requirements or specifications, but AC61-107B - Aircraft Operations at Altitudes Above 25,000 Feet Mean Sea Level or Mach Numbers Greater Than .75 / with Change 1 says (p. 33, emphasis in the original):

Only oxygen that meets or exceeds the Society of Automotive Engineers
(SAE) International Aerospace Standard AS8010 (as revised), Aviator’s
Breathing Oxygen Purity Standard, should be used.