Definition
An oxygen delivery system that supplies oxygen to the user's mask only when the user inhales, and delivers it under positive pressure at higher altitudes so that oxygen is forced into the lungs rather than relying on the user's breathing effort alone. It is used in aircraft operating at altitudes where a continuous-flow or simple demand system cannot maintain adequate blood oxygen levels.
Plain English
An oxygen system that only releases oxygen when you breathe in, and at very high altitudes pushes the oxygen into your lungs under pressure so your body still gets enough to function.
Context Anchor
Seen in high-altitude aircraft oxygen equipment, oxygen regulator descriptions, mask checks, and maintenance procedures.
Derivation
‘Pressure’ refers to the positive pressure used to force oxygen into the lungs at high altitude. ‘Demand’ means the system only delivers oxygen on inhalation, in response to the user’s breathing demand. The combined name describes a demand-type system with the added feature of pressurized delivery when needed.
Why Pilots Care
It prevents hypoxia by ensuring oxygen actually reaches the lungs when ambient pressure drops at altitude.
Grounding Statement
Picture taking a breath through a tight mask at very high altitude: the system senses the breath and supplies oxygen with enough push to help it enter your lungs.
Intuition Check
“Demand” does not mean the pilot asks for oxygen with a switch. Here, it means the user’s inhaling starts the oxygen flow.
Example Sentence 1
The technician inspected the pressure-demand oxygen system regulators during the scheduled high-altitude aircraft maintenance check.
Example Sentence 2
During inspection the technician verified regulator output on the pressure-demand oxygen system.