NFPA 418 section 4.3.2, Oxygen and other medical gases shall be stored and used in accordance with NFPA 99.
NFPA 418 section 4.3.3, Above ground flammable liquid storage tanks, compressed gas storage tanks, fuel storage tanks, and liquefied storage tanks shall be laterally located at least 50 feet from the edge of the FATO as defined in FAA AC 150/5390-2C Heliport Design Advisory.
Confusing yes, I think you need to go with 4.3.3