Which system is primarily affected during a cabin pressure loss?

During a cabin pressure loss, the oxygen system is primarily affected because the aircraft's pressurization relies on maintaining a specific pressure in the cabin to ensure the safety and comfort of the occupants at high altitudes. When cabin pressure is lost, the available oxygen in the atmosphere decreases, which can lead to hypoxia—a dangerous condition caused by insufficient oxygen. As a safety measure, pilots and passengers must use supplemental oxygen to maintain adequate oxygen levels in such situations.

The other systems, while vital for the overall operation of the aircraft, do not directly relate to the consequences of cabin pressure loss. The electrical and hydraulic systems are not directly impacted by changes in cabin pressure, and while the fuel system is crucial for the operation of the aircraft engines, it does not play a role in managing cabin pressure or the immediate needs of the crew and passengers under pressure loss conditions.