According to my chemistry textbook

[davidpt40]

According to my (college) chemistry textbook, humans can survive up to an altitude of 39,000 (thirty nine thousand) feet without supplimental oxygen.  That is considering that the human subject is not moving.

I know lots of B17 crewmembers passed out and died when their oxygen systems froze up.  Would they have survived if they had taken off their mask and passed out on the floor?  Maybe the CO2 build-up in the malfunctioning mask is what caused death.

[capt. apathy]

Would they have survived if they had taken off their mask and passed out on the floor?

probably just long enough to freeze to death

[RTR]

I rode the hyperbaric chamber while I was in the Airforce. My experience with altitiude is this. At 25,000ft with no supplimental O2 you can feel a need to breath. Your body demands more O2 than it is getting. It is very noticeable and uncomfortable. Given time (and not much of it) you will pass out, and un-aided you will die. I went for about 5 minutes before I plugged myself back into the O2. Some went a little longer, some went shorter. But we all went back on. (except one, who passed out and we had to plug him back in). I am sure that someone who is conditioned by familiarity with high altitudes would last considerably longer, however I am sure that the end result would be the same.

This is one of the reasons that modern ejection seats in aircraft will free fall to below 16,000ft before the man/seat seperation happens and the chute opens. Cold is another factor. At high altitude it is extremely cold, and the bodies demand for O2 increases.

As a side note...judgement gets pretty impaired as well.

Just my experience.
Cheers,
RTR

[Scootter]

Originally posted by RTR
I rode the hyperbaric chamber while I was in the Airforce. My experience with altitiude is this. At 25,000ft with no supplimental O2 you can feel a need to breath. Your body demands more O2 than it is getting. It is very noticeable and uncomfortable. Given time (and not much of it) you will pass out, and un-aided you will die. I went for about 5 minutes before I plugged myself back into the O2. Some went a little longer, some went shorter. But we all went back on. (except one, who passed out and we had to plug him back in). I am sure that someone who is conditioned by familiarity with high altitudes would last considerably longer, however I am sure that the end result would be the same.

This is one of the reasons that modern ejection seats in aircraft will free fall to below 16,000ft before the man/seat seperation happens and the chute opens. Cold is another factor. At high altitude it is extremely cold, and the bodies demand for O2 increases.

As a side note...judgement gets pretty impaired as well.

Just my experience.
Cheers,
RTR

You are correct sir,

The reason expeditions to Everest spent weeks working up to the summit from base camp to acclimate to low O2 levels. Now with lightweight supplemental o2 they do it faster.

The average man living below 3000 ft would die in about 8 min above 30k.
.

[Dinger]

Your textbook is wrong.

[mrblack]

When I did my Halo Jumps in the Army we used O2 at 24k:aok

[ra]

Originally posted by davidpt40
According to my (college) chemistry textbook, humans can survive up to an altitude of 39,000 (thirty nine thousand) feet without supplimental oxygen.  That is considering that the human subject is not moving.

I know lots of B17 crewmembers passed out and died when their oxygen systems froze up.  Would they have survived if they had taken off their mask and passed out on the floor?  Maybe the CO2 build-up in the malfunctioning mask is what caused death.

B-17's flew at about 25K feet, easily high enough to make crewmen pass out without O2, but probably not high enough to kill anyone.

39K is different.  Most people at that altitude would pass out in less than a minute, and probably be dead in five.

ra

[jigsaw]

Your book is so very wrong. Just ask Payne Stewart about hypoxic hypoxia.

Have your teacher go do one of the FAAs altitude chamber classes. It's not very expensive at all, and is one of the best training experiences I can recommend.

[Gunslinger]

the ACES II ejection seat performas man/seat seperation at 15,000ft.  If a pilot punches out above that he has about 15 min of breathable emergancy o2 and rides the seat down to 15,000 ft.  I think your textbook was written by somone who has never been that high up.

[davidpt40]

The human body requires a certain amount of oxygen.  The air at 39,000 feet above sea level has this amount.  Obviously there must be other factors that come in to play here.  

I'll type out the paragraph:

The human body at rest requires a partial pressure of O2 of at least .040 atm to sustain life, so sea level pressure supplies us with more than enough oxygen (.21atm) to live.  Is this true at, say, the top of Mt.Everest, 29000 feet (8900 meters), where the total air pressure equals .286 atms?
The P02 (P02= pressure of oxygen) of 0.079atm is still somewhat larger than the bare minimum needed to sustain life of .040 atm.  Why do so many who trek to Mt.Everest take along breathing equipment?  The figure of .040 atm assumes no additional demands for oxygen.  The hiker is at rest.  The oxygen demand when moving is higher, hence the need for supplemental oxygen.  Some mountaineers and guides have made it up to Mt.Everest without breathing apparatus.  The partial pressure of oxygen falls below .040 atm at an altitude above 12,000 meters (39,000 feet).  This means that passengers in a jet might barely survive a depressurization as high as 39,000 feet, though the safety margin dictates the use of oxygen masks well below that altitude.

Chemistry- A world of choices
Paul Kelter
James Carr Andrew Scott
Pg367-368

[NUKE]

Originally posted by davidpt40
This means that passengers in a jet might barely survive a depressurization as high as 39,000 feet, though the safety margin dictates the use of oxygen masks well below that altitude.

Chemistry- A world of choices
Paul Kelter
James Carr Andrew Scott
Pg367-368

What does being a passenger in a jet have to do with anything?

I'd say you would be dead w/o O2 at that alt, but what do I know.

[davidpt40]

I will answer your question with a question- What form of transportation puts millions of people per year 7 miles high in the air?

[NUKE]

I will answer your question with a question: What does transportation mode have to do with the human body's limitations when discussing O2 limits?

Does the crew of the "jet" have the same limits, or only the passengers?

[davidpt40]

The only reason a jet is mentioned is to make the example of humans at 39,000 feet more realistic.  It has nothing to do with anything else.

[GRUNHERZ]

I thought the jet example was pretty obvious - what chance could the passengers have to survive if the cabin was depressurized at 39k and no supplementary oxygen was provided.

I really dont see why you guys are arguning....