Everest

The news reported that the climbers who were trying to conquer Everest were killed. And they did not perish from the fall or injuries received as a result of climbing to the top. They died from lack of oxygen. Also it is asked, and in what sense was.
The Japanese climber was found dead in his tent on May 21, 2018. This was his 8th climb to Everest. The peak was never conquered by them.
I can understand when the falls or failures occur, but the amount of oxygen can be checked, is there the same device or does the oxygen supply run out? If he intends not to use oxygen, then why climb into the mountains. You can not breathe and lower, for example, wherever you are on the area. Create conditions without oxygen is not difficult. And try how much you can live. Strange ...
A person can not breathe. But you can conquer Everest! But not all of this is given.

By Joe Hastings - https://www.flickr.com/photos/joehastings/538538099/in/photolist-PA9BD-6e9mNF-KZFwM-KYKy6-66ZiD7-KYqcG-aQiEoD-4Ns87y-4Nserf-k2SBS-54Dvv6-4NnWf8-PfJe2-9vDwgE-4NsbtY-4PZBGk-4NnXyZ-aSqQdM-aCnihY-4NsaMC-4Nsbeh-4NnXSv-4NsbJ1-4NsaFy-bwhryJ-4NsaUW-b3Sz84-4Ns9oq-4Ns9xu-4NnYTk-b5BAJ6-4NnYu4-4Ns8W1-4Nsbkh-4NnXEM-4Nsb3m-4NsaYo-4Ns8sE-4Ns7j9-4NnZPe-4NsbCo-4NnV7i-bStsfM-Pfc9C-2PzCCz-k1U8Q-6VfVus-298BX-4WLbHu-4WFUZH, CC BY 2.0, Link