Which description matches a diluter-demand oxygen system?

• A. A system that delivers oxygen mixed with air to maintain constant partial pressure as altitude changes
• B. An oxygen system that provides only pure oxygen
• C. A system that measures cabin humidity
• D. Diluter-demand oxygen system

Answer: (D)

As altitude increases, the air becomes thinner and the partial pressure of oxygen drops. A diluter-demand oxygen system handles this by delivering a mixture of oxygen and ambient air, rather than pure oxygen, so the amount of oxygen in the breatheable mix is kept at a safe, constant partial pressure as you climb. It operates on demand—you breathe in and the system provides the breathable mix, diluting with outside air to maintain the target oxygen level. This precise mixing is what keeps your blood oxygen within safe limits at high altitude, without wasting oxygen.

That’s why the description describing oxygen delivered mixed with air to maintain constant partial pressure as altitude changes is the best fit. Pure oxygen systems deliver only oxygen and don’t automatically adjust with altitude; a system that merely measures cabin humidity isn’t about supplying breathable oxygen; the term diluter-demand alone doesn’t specify the functional mixing and on-demand delivery that defines how it works.