What is the death zone on Everest?

The death zone is the altitude where the human body can no longer adapt to the thin air and slowly starts to die, however well acclimatized it is. It is usually put at 8,000 m (26,247 ft)26,247 ft; our Everest guide draws the line at 7,500 m (24,600 ft)24,600 ft, where the deterioration already begins. On Everest it covers everything above the South Col on the Nepal side and above the North Col camps on the Tibet side, the last day or two of the climb.

What happens to the body

At the summit the air holds about a third of the oxygen it holds at sea level. Digestion slows and stops, sleep hardly comes, and the body burns its own reserves, losing weight by the hour. Thinking slows down, and the judgement a climber needs to turn back is the first thing to go. Fluid can collect in the lungs or the brain (HAPE and HACE). The rule is to spend as little time up there as possible, ideally no more than three days.

Why people die there

Most deaths on Everest's normal routes are not falls or avalanches. Climbers die of exhaustion, a heart attack or stroke, or the cold, often while still clipped to the fixed rope, and a twisted ankle or a failed headlamp can be fatal because nobody can carry a person down. Rescue above 8,000 m26.247 ft is the exception: the rescuers are in the same state. That is why the bodies of many climbers who died there remain on the mountain; carrying 80 to 90 kg down that terrain is beyond anyone.

How climbers survive it

Supplementary oxygen, a strict plan for when to turn back, and enough reserve to get down. How many oxygen bottles do I need on Everest? has the sums. The guide chapter Danger, Death Zone and turnaround is the one to read before deciding anything else, and What are HAPE and HACE? explains the two illnesses.