Oxygen-Enriched Atmosphere 4 : (Hcf-Hyp) For the purpose of this standard, and only for the purpose of this standard, an atmosphere in which the concentration of oxygen exceeds 23. 5 percent by volume
NFPA 99 Standard for Health Care Facilities, 2002 ed. https://law.resource.org/pub/us/cfr/ibr/004/nfpa.9 9.2005.pdf, (Std: Hlth Care Fcilty - Amer) {242 NFC}