How many types of onboard oxygen systems are described?

• A. Three
• B. Two
• C. One
• D. Four

Answer: (A)

Onboard oxygen delivery is described in three basic delivery methods depending on how and when oxygen is provided. Continuous-flow systems push oxygen to the mask at all times, regardless of whether you’re inhaling. This makes the system simple and immediate but wastes oxygen and isn’t ideal for efficiency at lower altitudes. Diluter-demand systems provide oxygen on inhalation and mix it with surrounding air, so you get enough oxygen when you breathe while conserving supply. Pressure-demand (or demand) systems deliver oxygen at the required pressure when you inhale, ensuring adequate oxygen at high altitudes where ambient pressure is low, though they are more complex and costly. Since the material outlines three distinct types, three is the correct count.