What is the reason for disconnecting from the aircraft oxygen system during an OBOGS inop situation?

Disconnecting from the aircraft oxygen system during an On-Board Oxygen Generating System (OBOGS) inoperative situation is primarily done to improve breathing capability and reduce the risk of suffocation. In circumstances where the OBOGS is not functioning properly, the supplied oxygen may not be adequate to sustain life at high altitudes or during emergency situations. By disconnecting from the malfunctioning system, the pilot or crew may have the option to revert to alternative oxygen supplies that are more reliable, ensuring that they can breathe more effectively and maintain situational awareness during critical phases of flight.

The emphasis on improving breathing capability highlights the urgent need to ensure that oxygen supply is adequate for survival, especially when flying at altitudes where ambient air is insufficient. Other options speak to considerations like conserving oxygen or maintaining cabin pressure, but the primary and immediate concern in an OBOGS inoperative situation is ensuring a reliable source of breathable air to prevent suffocation.