In which situation are oxygen masks required to be donned at 100%?

The requirement to don oxygen masks at 100% is particularly applicable in situations where there is smoke, fire, or fumes present in the cabin. This is crucial because inhaling any smoke or contaminated air can significantly impair the ability to breathe, and in such emergencies, it is vital to ensure that the oxygen being provided is uncontaminated.

In the presence of these hazardous conditions, using 100% oxygen helps to prevent the inhalation of harmful substances. The increased oxygen concentration enhances the efficacy of the oxygen provided, minimizing the risk of hypoxia and ensuring that passengers and crew can maintain their ability to function and potentially evacuate safely.

Other scenarios, while they may require the use of oxygen masks, do not specifically dictate the use of 100% oxygen; for instance, during a cabin fire, oxygen masks may be used, but their specific setting may vary based on the source of smoke and the situation's particulars. In the event of flight deck decompression, pilots are trained to respond with specific protocols that might not necessitate using 100% oxygen immediately, depending on the circumstances. Lastly, during an emergency landing, while oxygen masks are typically provided, the necessity for them to be set to 100% oxygen is contingent on the presence