What indication lights up if the oxygen system fails the BIT approximately 4 minutes after initial power up?

The OBOGS FAIL indication lights up when there is a failure in the On-Board Oxygen Generating System (OBOGS) during the built-in test (BIT). This specific light appears approximately 4 minutes after the initial power-up if the oxygen system encounters an issue that prevents it from functioning properly.

This is crucial for pilots as it warns them of a potential problem with their oxygen supply, which is essential for maintaining a safe and operable cockpit environment, especially at high altitudes where supplemental oxygen is required. Understanding the function of this indication is important for ensuring pilot safety and readiness to respond to oxygen system failures efficiently.

The other options represent different warning systems that activate under different conditions, but they do not specifically pertain to the OBOGS' functioning, making them less relevant in this scenario.