Editing Death zone (section)

==Supplemental oxygen==
[[File:Sauerstoffflasche.jpg|thumb|right|upright|Bottled oxygen can help mountaineers survive in the death zone]]
Mountaineers use supplemental oxygen in the death zone to reduce deleterious effects. An open-circuit oxygen apparatus was first tested on the [[1922 British Mount Everest expedition|1922]] and [[1924 British Mount Everest expedition|1924]] British Mount Everest expeditions; the bottled oxygen taken in [[1921 British Mount Everest reconnaissance expedition|1921]] was not used (see [[George Finch (chemist)|George Finch]] and [[Noel Odell]]).  In [[1953 British Mount Everest expedition|1953]] the first assault party of [[Tom Bourdillon]] and [[Charles Evans (mountaineer)|Charles Evans]] used closed-circuit oxygen apparatus. The second (successful) party of [[Edmund Hillary]] and [[Tenzing Norgay]] used open-circuit oxygen apparatus; after ten minutes taking photographs on the summit without his oxygen set on, Hillary said he "was becoming rather clumsy-fingered and slow-moving".<ref>{{cite book |last=Hunt |first= John |title= The Ascent of Everest |url=https://archive.org/details/ascentofeverest0000hunt |url-access=registration |year= 1953 |publisher= Hodder & Stoughton |location= London |page= [https://archive.org/details/ascentofeverest0000hunt/page/206 206] }} </ref> 

[[Physiologist]] [[Griffith Pugh]] was on the [[1952 British Cho Oyu expedition|1952]] and 1953 expeditions to study the effects of cold and altitude; he recommended acclimatising above {{cvt|15000|ft|order=flip}} for at least 36 days and the use of closed-circuit equipment.{{cn|date=May 2025}} He further studied the ability to acclimatise over several months on the [[1960–61 Silver Hut expedition]] to the Himalayas. 

In [[Timeline of Mount Everest expeditions#1978|1978]], [[Reinhold Messner]] and [[Peter Habeler]] made the first ascent of Mount Everest without supplemental oxygen.<ref>{{cite web|url=https://www.pbs.org/wgbh/nova/everest/history/firstwoo2.html|title=First without Oxygen|work=Nova|publisher=PBS|access-date=2025-05-17|archive-date=2025-05-17|archive-url=https://web.archive.org/web/20250517205812/https://www.pbs.org/wgbh/nova/everest/history/firstwoo2.html     |url-status=live}}</ref>