Oxygen Tanks on Everest: Not Required, But Often Used—Here's the Math

Climbing Everest does not require oxygen tanks. But most climbers use them above 7,000 m. Here's the nuance:

Physiology at Altitude

• Sea level: pO₂ = 21 kPa (21% of 101 kPa).
• Everest summit (8,849 m): pO₂ = 7 kPa — **33% of sea level**.
• Arterial O₂ saturation: Drops from 98% (sea level) to 50–70% (summit, no O₂). Cognitive/motor impairment severe.

Who Climbs Without O₂?

• Elite high-altitude mountaineers (Messner, Habeler, Loretan, Nims Purja, Kilian Jornet).
• <2% of summiters. Requires: genetic hypoxia tolerance, years of acclimatization, slow pace, low BMI.
• Risk: HACE/HAPE, frostbite (poor perfusion), death — mortality 2–3x higher than O₂ users.

Typical O₂ Regimen (Commercial Expeditions)

• Start: Camp 3 (7,200 m) or Camp 4 (7,900 m / South Col).
• Flow rate: 1–2 L/min (rest), 2–4 L/min (climbing).
• Bottles: 4–6 L carbon fiber (Poisk, Summit Oxygen). Each lasts 4–8 hrs at 2 L/min.
• Total per climber: 5–8 bottles (summit push + reserve). Sherpas carry 2–3 each.
• Cost: $500–$800/bottle (filled) + regulator/mask ($1,500).

Why "Not Required" ≠ "Not Needed"

Without O₂: summit day = 12–18 hrs in Death Zone. With O₂: 8–12 hrs, clearer decisions, warmer extremities, higher success rate (60% vs. 30% for non-O₂ on commercial teams).

Ethical Note

Discarded bottles litter the mountain (thousands). Some operators now require carry-down. "Clean climbs" gain respect.

O₂ on Everest is like a parachute: not mandatory, but jumping without one is a very specific kind of hubris.