Commercial Pilot License (CPL) Practice Exam

The correct answer is the diluter-demand mask, which is specifically designed to provide a flexible oxygen delivery system that allows for the mixing of 100% oxygen with ambient air. This capability is particularly beneficial for pilots and passengers flying at altitudes between 25,000 and 35,000 feet, where the partial pressure of oxygen is reduced, potentially leading to hypoxia.

At these altitudes, the diluter-demand mask automatically adjusts the oxygen delivered based on the wearer’s breathing pattern. When the user inhales, the mask supplies 100% oxygen; during exhalation, the mask allows exhaled air to escape, diluting the oxygen with ambient air. This method ensures that the individual receives the appropriate concentration of oxygen as required, optimizing oxygen usage and preventing the risks associated with hypoxia while maintaining comfort.

In contrast, other oxygen systems do not provide this dual capability. A pressure-demand mask requires a higher altitude and pressure to deliver oxygen, while a continuous flow mask delivers a steady stream of oxygen without regard for the breathing cycle, leading to waste and less efficiency at higher altitudes. The fixed slot mask is an older technology that does not provide the adaptability needed for varying altitude conditions.