Advanced hypoxia occurs at what altitude?

• A. 10,000 ft
• B. 14,000 ft
• C. 20,000 ft
• D. 37,000 ft

Answer: (B)

Advanced hypoxia happens when the brain isn’t getting enough oxygen due to the drop in the partial pressure of oxygen as you climb. As altitude rises, the amount of oxygen available in each breath decreases, so even with normal breathing your blood carries less oxygen to the brain. At around fourteen thousand feet, this lack becomes enough to noticeably impair thinking, reaction time, and coordination, which is why this level is used as the threshold for the advanced stage. The body’s quick fixes—faster breathing and higher heart rate—can’t fully counteract this at that height, so performance must be monitored and, if needed, supplemental oxygen or exposure reduction is required. Early signs typically appear closer to ten thousand feet, while at twenty thousand feet or higher the effects are far more severe, and at very high altitudes (like thirty-seven thousand feet) pressurization and oxygen systems are essential.