What safety measure is triggered at a cabin altitude above 13,500 feet?

When the cabin altitude exceeds 13,500 feet, the oxygen flow activation is an essential safety measure that ensures the well-being of passengers and crew. At these altitudes, the atmospheric pressure decreases, which can lead to hypoxia due to inadequate oxygen levels in the cabin. To counteract this, the oxygen system automatically activates, supplying supplemental oxygen to maintain a safe and breathable environment. This precaution is crucial for preventing physiological effects that can impair cognitive and motor functions, ensuring the safety of everyone onboard.

The activation at this altitude is a standard response in aviation safety protocols, underscoring the importance of efficient oxygen supply mechanisms when operating at higher elevations, making this answer the most appropriate choice for the question asked.