At what flight altitude must each air carrier flight deck crewmember be provided with a quick-donning type O2 mask?

The requirement for each air carrier flight deck crewmember to have access to a quick-donning type oxygen mask is established for safety during flight operations, particularly at higher altitudes where there is a risk of hypoxia due to reduced ambient oxygen levels.

At flight levels above 25,000 feet, the need for supplemental oxygen becomes critically important. Quick-donning oxygen masks can be donned rapidly, ensuring that crewmembers can respond quickly to situations such as cabin depressurization which may occur at those altitudes. This quick accessibility is essential to provide immediate oxygen supply to the crew, allowing them to maintain control of the aircraft while ensuring their oxygen needs are met.

While there are regulations regarding supplemental oxygen at lower altitudes, the specific requirement for a quick-donning mask is mandated at 25,000 feet. Above this altitude, the physiological changes that can occur require crews to be prepared for rapid descents or other emergencies where access to oxygen is crucial. Therefore, flight level 250 (25,000 feet) is where this requirement is specified, ensuring that flight crews are adequately equipped to handle high-altitude operations safely.