What is the requirement for supplemental oxygen above FL250?

The requirement for supplemental oxygen above Flight Level 250 is that each occupant on board must have access to at least 10 minutes of supplemental oxygen in the event of a decompression. This regulation is important because, at altitudes above 25,000 feet, the partial pressure of oxygen decreases, leading to a higher risk of hypoxia — a condition where the body does not receive enough oxygen. The 10-minute supply ensures that passengers and crew have enough time to descend to a safer altitude where supplemental oxygen is not necessary. This rule enhances safety and preparedness in the cockpit and cabin, ensuring that everyone can maintain consciousness and health until a safe altitude is reached.