The majority of mountaineers climbing above 25,000 feet use bottled, compressed oxygen, accessed via a face mask and tubing connected to a gas cylinder. The slopes of Everest are littered with discarded oxygen canisters; Sherpas are now incentivized to bring them down from Everest to help to reduce pollution.

The human body is susceptible to a huge range of complications when exposed to high altitude. Two of the most dangerous of these are HAPE, or high-altitude pulmonary edema, where there is excess fluid in the lungs, and HACE, or high-altitude cerebral edema, where there is excess fluid in the brain. Both of these require that the victim be immediately transported to a lower altitude, as well as obtain immediate medical help.

Hypoxia is a state where inadequate oxygen is available. Symptoms can include disorientation, confusion, extreme fatigue, susceptibility to cold, and death.