Thanks. That's as close as I will ever get to Mount Everest!
Here's an excerpt about the so-called "death zone" from the Wikipedia article about Mount Everest:
At the higher regions of Mount Everest, climbers seeking the summit typically spend substantial time within the death zone(altitudes higher than 8,000 metres (26,000 ft)), and face significant challenges to survival. Temperatures can dip to very low levels, resulting in frostbite of any body part exposed to the air. Since temperatures are so low, snow is well-frozen in certain areas and death or injury by slipping and falling can occur. High winds at these altitudes on Everest are also a potential threat to climbers.
Another significant threat to climbers is low atmospheric pressure. The atmospheric pressure at the top of Everest is about a third of sea level pressure or 0.333 standard atmospheres (337 mbar), resulting in the availability of only about a third as much oxygen to breathe.[111]
Debilitating effects of the death zone are so great that it takes most climbers up to 12 hours to walk the distance of 1.72 kilometres (1.07 mi) from South Col to the summit.[112] Achieving even this level of performance requires prolonged altitude acclimatization, which takes 40–60 days for a typical expedition. A sea-level dweller exposed to the atmospheric conditions at the altitude above 8,500 m (27,900 ft) without acclimatization would likely lose consciousness within 2 to 3 minutes.[113]
