Highest Altitude Without Pressuresuit

[samkent]

What is the highest altutude a human can survive for extended periods using..

1 Supplemental O2 (mask and tanks)
2 Cold weather clothing (coats - gloves - hats)
3 External heating (warming suits etc)

Just not a pressure suit. And not having to climb for weeks to get there.

[Ilya]

not having to climb for weeks to get there.

From which I assume you are talking about an aircraft.

If you are breathing pure oxygen, you could conceivably survive at pressure as low as 0.16 atm, which is 13,000 meters. At that pressure water boils at 74 C, so your blood will not boil, but you will need to pre-breath pure oxygen for a significant time before ascent, lest you are in danger of decompression sickness. That's not a problem for mountain climbers, since they ascend so much slower than an aircraft.

Of course, if your oxygen supply fails, you will pass out in seconds.

[grant hutchison]

Highest permanent human habitation is at around 5000m altitude, where the barometric pressure is around half sea level, making the oxygen partial pressure equivalent to breathing about 10% oxygen at sea-level.
Folk at that altitude survive the temperature quite nicely with just adaptive behaviour (warm clothing, keeping out of the wind, etc). The only time you would need external heating, in any setting, would be if you weren't well enough insulated by clothing.
If we take that 0.1 atmospheres of oxygen as the limit for long-term survival, you could live a normal life span at 0.1 atmospheres barometric pressure breathing pure oxygen. If I'm figuring the scale height properly, that's equivalent to about 17000m altitude. This is still lower than the Armstrong Limit, at 19000m, where water boils at body temperature, so a pressure suit would not be required.

Grant Hutchison

[Warren Platts]

Highest permanent human habitation is at around 5000m altitude, where the barometric pressure is around half sea level, making the oxygen partial pressure equivalent to breathing about 10% oxygen at sea-level.
Folk at that altitude survive the temperature quite nicely with just adaptive behaviour (warm clothing, keeping out of the wind, etc). The only time you would need external heating, in any setting, would be if you weren't well enough insulated by clothing.
If we take that 0.1 atmospheres of oxygen as the limit for long-term survival, you could live a normal life span at 0.1 atmospheres barometric pressure breathing pure oxygen. If I'm figuring the scale height properly, that's equivalent to about 17000m altitude. This is still lower than the Armstrong Limit, at 19000m, where water boils at body temperature, so a pressure suit would not be required.

Grant Hutchison

No smoking allowed though!

[samkent]

I guess paper airplanes are no fun at that altitude.

[Warren Platts]

I guess paper airplanes are no fun at that altitude.

Really, so that would make the shores of the Dead Sea paper airplane heaven.

[Casus_belli]

I seem to remember that a Spitfire pilot managed an altitude of 45,000 ft breathing pure oxygen in an un-pressurised cockpit.

[neilzero]

It likely varies with the person and the preconditioning. It also depends on weather extended period is a few hours or a few years. My guess is most people would die of something within a year at 1/10 th bar of 98% oxygen = 1.47 psi. Dry skin would be one of the problems even at 100% relative humidity which I think is less than 2% water vapor, even at 90 degrees f and 1/10 th bar.
90 degrees f would likely be less comfortable than naked at 40 degrees f. Waste body heat disposal is difficult at low pressure. Neil

[joema]

Exposure duration, partial pressure O2, altitude and individual condition are all factors. The below graphs show an acclimatized person could probably survive extended periods at 45,000 ft (13,716 m) breathing pure O2 at 2 psi.

I don't know if that assumes "positive pressure breathing", where the O2 is forced into your lungs and you work to exhale, vs a normal "demand breathing" regulator.