What is the time of useful consciousness at 35,000 feet?

The time of useful consciousness is a critical concept in aviation, particularly concerning hypoxia, which can occur at high altitudes where the oxygen levels are significantly reduced. At 35,000 feet, the effective available oxygen for human respiration diminishes to a point where a lack of supplemental oxygen can lead to unconsciousness or impaired cognitive function very quickly.

The correct response indicating a time of 30-50 seconds reflects the reality that at this altitude, an unprotected individual would typically have about half a minute to less than a minute to act before losing consciousness. Factors such as individual physiology and activity level can influence this duration, but the average time frame recognized in training and safety protocols places it firmly within that 30 to 50-second range.

Understanding this time frame is vital for pilots and crew members, as it underscores the urgency of deploying oxygen masks or initiating emergency procedures when cabin pressure loss occurs at cruising altitudes.