Under what conditions is the use of the "Emergency Oxygen" system mandated?

The use of the "Emergency Oxygen" system is mandated when cabin pressure exceeds safe limits. This situation typically occurs when there is a rapid decompression or a failure in the pressurization system, which could jeopardize the safety and health of the crew and passengers. In such circumstances, the ambient air outside the aircraft can become inadequate to breathe, potentially leading to hypoxia. The emergency oxygen system provides necessary supplemental oxygen to maintain consciousness and enable safe operation of the aircraft.

Takeoff procedures and landing do not inherently require the use of the emergency oxygen system unless specific circumstances arise that compromise cabin pressure. Low visibility conditions, while they pose operational challenges, do not directly necessitate the oxygen system either, as these conditions are more related to navigation and safe aircraft handling rather than issues concerning cabin pressure and oxygen availability.