Which oxygen flow condition is indicated by the PX Oxygen AUTO setting?

The PX Oxygen AUTO setting is designed to automatically provide oxygen when the cabin altitude exceeds a certain threshold, specifically over 14,500 feet. This setting is vital for ensuring that passengers and crew remain safe and oxygenated in an environment where the air pressure is insufficient for normal respiration.

At cabin altitudes above 14,500 feet, supplemental oxygen is necessary due to the reduction in available oxygen to breathe. The AUTO function activates the oxygen system seamlessly, which means that as the aircraft ascends and the cabin altitude surpasses this level, oxygen is automatically supplied. This is crucial for preventing hypoxia, where the body does not receive enough oxygen.

In contrast, the other conditions listed do not accurately represent the mechanics of the AUTO setting. For example, constant flow and restricted flow are not relevant to the AUTO function, as it is specifically intended to activate under the condition of elevated cabin altitudes. This automatic response helps ensure that oxygen is provided when needed, aligning with safety protocols in aviation.