FAA Office of Aerospace Medicine 
Civil Aerospace Medical Institute

Report No: DOT/FAA/AM-25/52

Title and Subtitle: Low Flow / Optimized Flow Oxygen Systems for Passengers – (OFOS) - A Physiologic Inquiry into Emergency Supplemental Oxygen Supply Needs and Procedures

Report Date: 9/1/2025

Authors: Dr. James E. Campbell (ORCID 0000-0002-4062-4710) Dr. Susan M. Jay (ORCID 0000-0002-1331-0396)

Abstract: The OFOS study evaluated SpO2 values and oxygen flow rates via FAA-approved phase-dilution passenger oxygen masks at simulated cabin altitudes between 12K’ and 45K’. Results favor establishment of performance-based, physiological criteria (e.g., range of SpO2 values) that can be used as a minimum performance standard for the minimum mass flow of supplemental oxygen to a passenger mask for adequate hypoxia protection. OFOS data demonstrate significantly higher stable human blood oxygenation levels are maintained through use of a phase-dilution passenger oxygen mask than is required by 14 CFR 25.1443(c)(2) regulation, and a brief transit as a passenger to 45k’ while breathing oxygen from a PAX mask is tolerable (SpO2 does not fall below 14 CFR 25.1443 (c)(2) regulation guidelines). OFOS data support, 1) 14 CFR 25.1443(c)(2) regulation modification in favor of SpO2 focus, 2)use of less oxygen as a result of SpO2 focused findings, 3) fuel/cost-savings, 4) less CO2 emissions, and 5) evidence that passengers are adequately protected under circumstances of a gradual decompression to 45K’ pressure-altitude if exposed for less than 1 minute (validation of FAA Memorandum ANM-03-112-16 (24 MAR 2006)). As a result of this evidence, if more aircraft are type-certified for 45K’ flight, then overall safety will improve as a result of decongested NAS national airspace.

Key Words: Passenger Oxygen Mask Continuous Flow Pressure Altitude Hypobaric Chamber Tracheal Partial Pressure 8025A Ernsting 25.841 25.1443 TSO C64a Decompression TPP Blood Saturation SpO2 45000 45k hematocrit hemoglobin physiology AS5722 human PAX

No. of Pages: 75