How much supplemental oxygen for emergency descent must a pressurized turbine-powered air transport airplane carry for each flight crewmember on flight deck duty above 10,000 feet?

For pressurized turbine-powered air transport airplanes, the regulation governing supplemental oxygen requirements stipulates that a minimum of a 2-hour supply of oxygen must be available for each flight crewmember on flight deck duty when flying at altitudes above 10,000 feet. This requirement is in place to ensure that in the event of a loss of cabin pressure, each crew member has sufficient oxygen to maintain consciousness and perform necessary emergency procedures during an emergency descent.

The rationale behind this specific duration is to provide an adequate safety margin, ensuring that even if an emergency occurs, there is enough oxygen not only for descent but also for any necessary actions taken during that timeframe, such as communicating with air traffic control or preparing the aircraft and passengers for the emergency.