According to the Food and Drug Administration Safety and Innovation Act (FDASIA), XI, Subtitle B, sections 575 and 576, gases for direct administration to human beings or animals have to be certified as medical gases.
Recently, the FDA has published a new Guideline as a draft on that topic which details this certification process. For the FDA, certifiable gases are: nitrogen, oxygen, carbon dioxide, helium, Nitrous oxide and air. An additional requirement has to be met, i.e. complying with the requirements of the respective compendia. Here, the FDA refers to the US Pharmacopoeia (USP), the Homœopathic Pharmacopœia of the United States (HPUS) as well as to the National Formulary (NF).
The certification of a medical gas has to take place before the placing on the market for human/veterinary use otherwise the gas is considered as a new non-authorised medical product.
Normally, the producer of the medical gas submits the application for certification. An application form for certification is included in the Guideline. Information like type of gas, place of manufacture, a short description of the manufacturing process as well as further measures taken to ensure purity and quality, etc. have to be provided. The FDA indicates a 60-day deadline for the certification process.
You can find the draft of the Guideline on Certification Process for Designated Medical Gases on the FDA website.