Why is cabin pressurization necessary at altitude?

Why is cabin pressurization necessary at altitude?

• A. Keeps outside air out of the cabin
• B. Maintains safe cabin pressure for crew comfort and oxygenation
• C. Heats the cabin to room temperature
• D. Improves wing lift

Answer: (B)

At altitude the air is too thin to provide enough oxygen for safe breathing, so the cabin is pressurized to a breathable level—typically equivalent to being at about 6,000–8,000 feet. This keeps the partial pressure of oxygen in the cabin high enough for normal oxygen uptake, preventing hypoxia and making it comfortable for crew and passengers during flight. Pressurization is not about keeping outside air out, heating the cabin, or improving wing lift—the first is a separate function of filtration and sealing, the second is handled by the environmental control system, and the last depends on aerodynamics and airspeed.

At altitude the air is too thin to provide enough oxygen for safe breathing, so the cabin is pressurized to a breathable level—typically equivalent to being at about 6,000–8,000 feet. This keeps the partial pressure of oxygen in the cabin high enough for normal oxygen uptake, preventing hypoxia and making it comfortable for crew and passengers during flight. Pressurization is not about keeping outside air out, heating the cabin, or improving wing lift—the first is a separate function of filtration and sealing, the second is handled by the environmental control system, and the last depends on aerodynamics and airspeed.