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Pressure Demand Aviation Oxygen Systems

Pressure-Demand-Oxygen-System-aircraftPressure Demand Oxygen System – A demand oxygen system that supplies 100 percent oxygen at sufficient pressure above the altitude where normal breathing is adequate. Also referred to as a pressure breathing system.

Pressure-Demand Oxygen Systems  are similar to diluter demand oxygen equipment, except that oxygen is supplied to the mask under pressure at cabin altitudes above 34,000 feet. Pressure-demand regulators create airtight and oxygen-tight seals, but they also provide a positive pressure application of oxygen to the mask face piece that allows the user’s lungs to be pressurized with oxygen. This feature makes pressure demand regulators safe at altitudes above 40,000 feet. Some systems may have a pressure demand mask with the regulator attached directly to the mask, rather than mounted on the instrument panel or other area within the flight deck. The mask-mounted regulator eliminates the problem of a long hose that must be purged of air before 100 percent oxygen begins flowing into the mask.


  1. Why above 34,000 ft ?

  2. Good question!
    It’s because at 34,000 feet 100% oxygen is needed to get the same partial pressure of oxygen into your lungs that you would get at sea level. The pressure at 34k is about 1/4 of the pressure at sea level.

    As the cabin altitude increases above 34K, the lungs will absorb less oxygen even though you are receiving 100%. The pressure demand system pressurizes the 100% oxygen in your lungs allowing for the maximum absorption available.

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