What action should be taken if descent below 10,000 feet MSL is initiated?

When a descent below 10,000 feet mean sea level (MSL) is initiated, the appropriate action often involves deploying supplemental oxygen systems, particularly in scenarios where cabin pressure might not be adequately maintained or if there are specific protocols to follow for crew and passengers in terms of safety. The function of the Green Ring indicates the procedure to activate emergency oxygen systems should they be needed, particularly in the event of sudden decompression or if cabin altitude exceeds safe limits for unprotected personnel.

Undergoing rapid descent can lead to various physiological effects, and the deployment of oxygen can mitigate risks associated with altitude and reduced oxygen availability. This is essential to maintain cognitive function and physical performance during periods of possible hypoxia.

While the other options may represent valid considerations in different circumstances, they are not the immediate procedural focal point when a descent below 10,000 feet is initiated, particularly in the context of enhanced safety measures during descent. Proper oxygen management ensures that all personnel can maintain their functionality and safety during such maneuvers.