SACAA NPL Human Performance Practice Questions - SACAA National Pilot Licence (NPL) Human Performance & Limitations Examination Exam

The partial pressure of oxygen decreases in direct proportion to the decrease in total atmospheric pressure, even though the percentage of oxygen remains constant at ~21%. The partial pressure of oxygen increases because the percentage of oxygen in the air rises at higher altitudes. The partial pressure of oxygen remains completely constant up to the tropopause because atmospheric pressure is uniform. The partial pressure of oxygen decreases because oxygen molecules sink to lower altitudes while nitrogen rises.