What is the Time of Useful Consciousness at 18,000 feet during rapid decompression?

Time of Useful Consciousness (TUC) refers to the duration a person can function effectively at high altitudes before losing consciousness due to hypoxia—a deficiency of oxygen reaching the tissues. At 18,000 feet, the atmospheric pressure is significantly lower than at sea level, which reduces oxygen levels available to the body.

The correct choice indicates a TUC of 20-30 minutes at this altitude. This is based on studies and data that have shown that, while individuals may initially feel fine, their ability to think clearly and perform tasks diminishes as they begin to experience symptoms of hypoxia. It is important to note that individual responses may vary due to factors such as physical fitness, health, and acclimatization levels, but this range is generally accepted for most people, making the estimate of 20-30 minutes realistic for the scenario described.

As altitude increases beyond this point, TUC decreases significantly, which is why understanding these specifics is crucial for aviation crew members, particularly in the context of rapid decompression scenarios.