How long can you survive at high altitude?
How long can you survive at high altitude?
Indefinitely up to about 5,500 metres if you acclimatise. Above 8,000 metres the body only deteriorates.
Indefinite below ~5,000 m with acclimatisation; hours to days above 8,000 m
Air is 21 per cent oxygen at every altitude — what falls is pressure, and with it the amount of oxygen each breath delivers. Acclimatisation works: over days to weeks the body makes more red cells, breathes deeper and adjusts blood chemistry, which is how permanent settlements exist at 4,000-5,000 metres in the Andes and Himalaya. The highest permanent human habitation sits around 5,100 metres, and above roughly 5,500 metres people lose weight and condition continuously no matter how long they stay. Ascending faster than the body can adjust causes acute mountain sickness, which can progress to high-altitude pulmonary or cerebral oedema — both potentially fatal within hours and both treated the same way, by descending. Above 8,000 metres, acclimatisation stops being possible at all.
What happens, in order
| When | What |
|---|---|
| 2,500-3,500 m | Acute mountain sickness common if ascent is rapid: headache, nausea, poor sleep |
| 3,500-5,500 m | Acclimatisation possible; permanent habitation exists up to about 5,100 m |
| 5,500-8,000 m | Continuous deterioration; weight and strength are lost steadily |
| Above 8,000 m | The death zone — no acclimatisation is possible |
What changes the figure
- Slow ascent with rest days is the single most effective measure
- Descent reverses altitude illness faster than any drug
- Supplemental oxygen effectively lowers the mountain by 1,000-1,500 metres
Thresholds compiled from published high-altitude medicine guidance; individual tolerance varies substantially.
Physiology, not instruction. Every figure here is a population range under particular conditions, and individual variation is large — temperature, exertion, fitness and health move all of them substantially. Nothing on this page is medical advice.
Conditions
- Can you survive being struck by lightning? Usually, yes — around nine in ten people struck by lightning survive, though many are left with lasting injuries.
- How long can you survive in freezing water? Around an hour before unconsciousness in water near 0 °C — but the first minute is the one that kills most people.
- What happens to your body in a vacuum? You do not explode. Consciousness goes in about fifteen seconds from oxygen leaving the blood.
- How long can you survive in extreme heat? It depends on humidity more than temperature — once the wet-bulb temperature reaches about 35 °C, sweating cannot cool you at all.
- How long can you survive in extreme cold? Hours in still air with dry clothing; under an hour in wind at -30 °C — and people have survived core temperatures near 12 °C.
- How much radiation can a human survive? Below about 1 sievert most people recover; around 4.5 sieverts kills roughly half; above 8 sieverts survival is very rare.
- How long can you survive carbon monoxide exposure? Hours at low concentrations, minutes at high ones — and it has no smell, colour or taste to warn you.
- How long can you survive in a house fire? Around three minutes in a modern room before flashover, and smoke rather than flame is what kills most people.
- How loud does a sound have to be to kill you? Sound alone cannot exceed about 194 dB in air — beyond that it is a blast wave, and blast is what causes injury.
- How deep can a human go before pressure kills them? About 200 metres on a single breath, around 60-70 metres on air, and roughly 500-700 metres in a saturation chamber.
- How much g-force can a human survive? About 4-6 g sustained before blacking out, 9 g in a pressure suit, and over 100 g briefly in a crash.
- How much electricity can a human survive? Current decides it, not voltage — around 100 milliamps through the chest can stop the heart.
- How long can you survive in boiling water? No meaningful time. Water at 100 °C causes full-thickness burns instantly, and burns over a large area are fatal.
- How long can you survive if an aircraft cabin decompresses? Roughly 30 to 60 seconds of useful consciousness at 35,000 feet — which is why the mask goes on before helping anyone else.
Common questions
- How long can you survive at high altitude?
- Indefinitely up to about 5,500 metres if you acclimatise. Above 8,000 metres the body only deteriorates.
- What changes how long?
- Slow ascent with rest days is the single most effective measure Descent reverses altitude illness faster than any drug Supplemental oxygen effectively lowers the mountain by 1,000-1,500 metres
Related pages
- Can you survive being struck by lightning? Usually, yes — around nine in ten people struck by lightning survive, though many are left with lasting injuries.
- How long can you survive in freezing water? Around an hour before unconsciousness in water near 0 °C — but the first minute is the one that kills most people.
- What happens to your body in a vacuum? You do not explode. Consciousness goes in about fifteen seconds from oxygen leaving the blood.
- How long can you survive in extreme heat? It depends on humidity more than temperature — once the wet-bulb temperature reaches about 35 °C, sweating cannot cool you at all.
- How long can you survive in extreme cold? Hours in still air with dry clothing; under an hour in wind at -30 °C — and people have survived core temperatures near 12 °C.
- How much radiation can a human survive? Below about 1 sievert most people recover; around 4.5 sieverts kills roughly half; above 8 sieverts survival is very rare.
- How long can you survive carbon monoxide exposure? Hours at low concentrations, minutes at high ones — and it has no smell, colour or taste to warn you.
- How long can you survive in a house fire? Around three minutes in a modern room before flashover, and smoke rather than flame is what kills most people.
- How long can you survive without water? Going without something
- How long can you survive without food? Going without something
- How long can you survive without air? Going without something
- How long could you survive in deep space? Places
- How long can you survive without sleep? Going without something
- Could you survive on Mars? Places
Sources
- Typical range compiled from manufacturer specifications — At One Place