hi alt oxygen

Thank you for the information. Very interesting!

On Wed, 10 Mar 2004 11:46:52 -0500, "Leslie Swartz"
wrote:

You live off off something called the "partial pressure of oxygen" in the
medium you are breathing. As altitude increases, the partial pressure of
oxygen in air decreases. Therefore, you must "enrich" the breathing medium
with more oxygen in order to achieve the *same* partial pressure of oxygen
that exists at lower altitudes.

Two solutions: 1) increase the relative percentage of oxygen inht e
medium, or 2) pressurize hte medium. 1) is much less expensive than 2).

Steve Swartz

(The partial pressure of oxygen is what gets the O2 across your lung tissue
into your bloodstream. As total pressure decreases, the partial pressure of
oxygen decreases. Eventually, as ambient pressure goes down, you would need
to breathe pure *pressurized* [3.2 psi IIRC] oxygen in order to make up the
deficit.)

"Arquebus257WeaMag" wrote in message
om...
Im just wondering why pure oxygen is used for high altitude flying
instead of regular air. I thought prolonged exposures to breathing
pure oxygen can be harmfull as you can become oxygen dependant.


all the best -- Dan Ford
email: (requires authentication)

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

Here's some quick and dirty info on oxygen - normally about 1/5 of
'air'. So the 'partial pressure' is 1/5 of 29.92 inches/760 mm Hg
equalling 152mm O2. The ambient air pressure drops by 1/2 every 18,000
feet (roughly). So at sea level you get 1/5 of 760mm; at 18,000 you
get 1/5 of 380mm. At about 34000 you get the equivalent of sea level
oxygen partial pressure breathing 100% oxygen. If you keep going on up
pretty soon you reach a dangerously low level of partial pressure -
that's at about 41,000. So modern diluter-demand O2 regulators start
feeding you oxygen under pressure. Easy to inhale - you have to work
to exhale. This gets worse as you keep going up. At 50,000 cabin
pressure it is physically demanding to exhale and the mask has to be
very tightly strapped on your face. Not to mention painful. Note that
so far we don't have any 'cabin pressure' - air bled from the
engine(s) to remedy the situation. Also as you keep climbing into
areas of lesser pressure water boils at progrssively lower
temperatures. At 63,000 ambient pressure water boils at 98.6F/37C -
body temp. That means your lungs are now filled with water vapor and
you can no longer absorb oxygen. Hence pressure cabins and pressure
suits over 50,000 feet. Breathing pure oxygen for extended periods of
time is a hassle. First, there is no water in Aviator's oxygen - can't
take the chance of water freezing in the lines. Therefore every breath
you're becoming more and more dehydrated. Second, oxygen can flood the
inner ears (through the eustachian tubes) and late at night in bed
that oxygen gets absorbed by the blood and you wake up with giant
earaches. Third, if you're breathing pure O2 and pulling lots of G -
the lower airsacs in your lungs tend to stick together because with
pure O2 you're not breathing as deeply. Back on the ground when you
take a deep breath it feels as if someone just knifed you. This is
termed 'atelactasis'.
Now, oxygen is used to keep pilots crew and passengers functioning at
more or less an efficient level. Rule of thumb - O2 over 10,000 feet.
There is a 'cheat' where one can got to 12 for 30 minutes. But the
brain needs O2 to function properly. With hard training one can
function adequately at higher altitudes. But even the best can screw
up - read 'Into Thin Air'. FWIW I used to teach this stuff.
Walt BJ

Subject: hi alt oxygen
From: (WaltBJ)
Date: 3/10/04 9:12 PM Pacific Standard Time
Message-id:

Here's some quick and dirty info on oxygen - normally about 1/5 of
'air'. So the 'partial pressure' is 1/5 of 29.92 inches/760 mm Hg
equalling 152mm O2. The ambient air pressure drops by 1/2 every 18,000
feet (roughly). So at sea level you get 1/5 of 760mm; at 18,000 you
get 1/5 of 380mm. At about 34000 you get the equivalent of sea level
oxygen partial pressure breathing 100% oxygen. If you keep going on up
pretty soon you reach a dangerously low level of partial pressure -
that's at about 41,000. So modern diluter-demand O2 regulators start
feeding you oxygen under pressure. Easy to inhale - you have to work
to exhale. This gets worse as you keep going up. At 50,000 cabin
pressure it is physically demanding to exhale and the mask has to be
very tightly strapped on your face. Not to mention painful. Note that
so far we don't have any 'cabin pressure' - air bled from the
engine(s) to remedy the situation. Also as you keep climbing into
areas of lesser pressure water boils at progrssively lower
temperatures. At 63,000 ambient pressure water boils at 98.6F/37C -
body temp. That means your lungs are now filled with water vapor and
you can no longer absorb oxygen. Hence pressure cabins and pressure
suits over 50,000 feet. Breathing pure oxygen for extended periods of
time is a hassle. First, there is no water in Aviator's oxygen - can't
take the chance of water freezing in the lines. Therefore every breath
you're becoming more and more dehydrated. Second, oxygen can flood the
inner ears (through the eustachian tubes) and late at night in bed
that oxygen gets absorbed by the blood and you wake up with giant
earaches. Third, if you're breathing pure O2 and pulling lots of G -
the lower airsacs in your lungs tend to stick together because with
pure O2 you're not breathing as deeply. Back on the ground when you
take a deep breath it feels as if someone just knifed you. This is
termed 'atelactasis'.
Now, oxygen is used to keep pilots crew and passengers functioning at
more or less an efficient level. Rule of thumb - O2 over 10,000 feet.
There is a 'cheat' where one can got to 12 for 30 minutes. But the
brain needs O2 to function properly. With hard training one can
function adequately at higher altitudes. But even the best can screw
up - read 'Into Thin Air'. FWIW I used to teach this stuff.
Walt BJ


I was just glad to get rid of the high pressure system with the spitbag to the
low pressure demand mask. It doesn't take much to make me happy.


Arthur Kramer
344th BG 494th BS
England, France, Belgium, Holland, Germany
Visit my WW II B-26 website at:
http://www.coastcomp.com/artkramer

There is a 'cheat' where one can got to 12 for 30 minutes. But the
brain needs O2 to function properly. With hard training one can
function adequately at higher altitudes.

Pensacola. Low pressure tank. 30,000 feet pressure. Instructor asks for
volunteer. (I tend to do dumb things) I said OK. "Please take this pencil
and write your name on this clipboard." "How many times?" "Don't worry. I'll
tell you when to stop."

Off comes mask. I write and I write and at the 4th perfect signature I stop --
wondering why am I doing this. "Hell, I can do this for the rest of my life."
(30,00 feet. Yeah) Instructor slams mask back on. My vision instantly
changed from looking down a soda straw to wide open, COLOR!, side vision. Wow!
Last signature was a straight line. (Hmmmm. Looked OK at the time.)

At 30K, one has about 4 seconds of useful consciousness -- unless one holds
one's breath. That may net one a couple of seconds more. No pain. No strain.
Quite pleasant. Been there. Done that. Fast and almost fun.

Humans need a constant supply of oxygen and we store almost none. Lack of
oxygen doesn't hurt. What hurts and gives the feeling of strangulation is an
overabundance of carbon dioxide. Want to know what too much CO2 feels like?
Hold your breath for 3-4 minutes.

Throw in a little exhaust gas and the ceiling easily drops to 20K or lower.

Quent

(QDurham) wrote:

There is a 'cheat' where one can got to 12 for 30 minutes. But the
brain needs O2 to function properly. With hard training one can
function adequately at higher altitudes.

Pensacola. Low pressure tank. 30,000 feet pressure. Instructor asks for
volunteer. (I tend to do dumb things) I said OK. "Please take this pencil
and write your name on this clipboard." "How many times?" "Don't worry. I'll
tell you when to stop."

Off comes mask. I write and I write and at the 4th perfect signature I stop --
wondering why am I doing this. "Hell, I can do this for the rest of my life."
(30,00 feet. Yeah) Instructor slams mask back on. My vision instantly
changed from looking down a soda straw to wide open, COLOR!, side vision. Wow!
Last signature was a straight line. (Hmmmm. Looked OK at the time.)

At 30K, one has about 4 seconds of useful consciousness -- unless one holds
one's breath. That may net one a couple of seconds more. No pain. No strain.
Quite pleasant. Been there. Done that. Fast and almost fun.

Humans need a constant supply of oxygen and we store almost none. Lack of
oxygen doesn't hurt. What hurts and gives the feeling of strangulation is an
overabundance of carbon dioxide. Want to know what too much CO2 feels like?
Hold your breath for 3-4 minutes.

Throw in a little exhaust gas and the ceiling easily drops to 20K or lower.

Quent

Yes, this is exactly correct...the Canadian Armed Forces has this
tank setup in Trenton Ontario. The short course is called HAI for
'high altitude indoctrination' and the effects are as Quent
mentions.

In addition to what he says the effects of hypoxia onset versus
altitude is very un linear. The armed Forces mandate oxygen use
above 10,000 ft but you can easily survive for very long periods
at 20,000 while sitting quietly (I've done it) but increase this
altitude by only slightly and bad things start to happen rapidly,
right down to several seconds of consciousness at 30k.
--

-Gord.

Subject: hi alt oxygen
From: "Gord Beaman" )
Date: 3/11/04 10:07 AM Pacific Standard Time
Message-id: 8o91509jd5cda3kuuemn759

n addition to what he says the effects of hypoxia onset versus
altitude is very un linear. The armed Forces mandate oxygen use
above 10,000 ft but you can easily survive for very long periods
at 20,000 while sitting quietly (I've done it) but increase this

Sure. But you can't operate a bombsight with any degree of accuracy under those
conditions. Keep your mask on. And at night from the ground up.


Arthur Kramer
344th BG 494th BS
England, France, Belgium, Holland, Germany
Visit my WW II B-26 website at:
http://www.coastcomp.com/artkramer

In article , ArtKramr
writes
Subject: hi alt oxygen
From: "Gord Beaman" )
Date: 3/11/04 10:07 AM Pacific Standard Time
Message-id: 8o91509jd5cda3kuuemn759

n addition to what he says the effects of hypoxia onset versus
altitude is very un linear. The armed Forces mandate oxygen use
above 10,000 ft but you can easily survive for very long periods
at 20,000 while sitting quietly (I've done it) but increase this

Sure. But you can't operate a bombsight with any degree of accuracy under those
conditions. Keep your mask on. And at night from the ground up.


Arthur Kramer
344th BG 494th BS
England, France, Belgium, Holland, Germany
Visit my WW II B-26 website at:
http://www.coastcomp.com/artkramer


Just out of interest, Art, did you ever have to use the A-7 mask (and
presumably a throat mike?) or was the A-14 in universal use while you
were operational?

Cheers,

Dave

--
Dave Eadsforth

On 10 Mar 2004 21:12:59 -0800, (WaltBJ) wrote:

Rule of thumb - O2 over 10,000 feet.

It used to amuse me, in the days before the Eisenhower Tunnel, that
the highway over Loveland Pass in CO took the driver above the
altitude at which the USAF wanted pilots to use oxygen masks.

At Aspen of course we skied all winter at above 11,000 feet. (At
Loveland, the parking lot was higher than that.) Do you suppose that's
why ski bums are famously so unstable?


all the best -- Dan Ford
email: (requires authentication)

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

Cub Driver wrote:

On 10 Mar 2004 21:12:59 -0800, (WaltBJ) wrote:

Rule of thumb - O2 over 10,000 feet.

It used to amuse me, in the days before the Eisenhower Tunnel, that
the highway over Loveland Pass in CO took the driver above the
altitude at which the USAF wanted pilots to use oxygen masks.

At Aspen of course we skied all winter at above 11,000 feet. (At
Loveland, the parking lot was higher than that.) Do you suppose that's
why ski bums are famously so unstable?

The difference being the rate at which you ascend from lower altitudes,
although the military's 10,000 foot rule seems very conservativ. IIRR,
even the FAA allows pilots to fly between 12,500 and 14,000 ft. for 1/2 an
hour without O2, and pax can do it indefinitely. Pity the poor fighter
pilots in WW1, who used to climb up to 17-20,000 feet without O2 and
patrol there for an hour or so in open, unheated cockpits. And suffered
massive headaches as a result.

Guy

Guy Alcala wrote:

The difference being the rate at which you ascend from lower altitudes,
although the military's 10,000 foot rule seems very conservativ. IIRR,
even the FAA allows pilots to fly between 12,500 and 14,000 ft. for 1/2 an
hour without O2, and pax can do it indefinitely. Pity the poor fighter
pilots in WW1, who used to climb up to 17-20,000 feet without O2 and
patrol there for an hour or so in open, unheated cockpits. And suffered
massive headaches as a result.


Ah, memories come back ... in my old freight dog days I used to fly with
an older guy who hated to waste fuel on pressurization while crossing
the Rockies in Montana. His only complaint was that he had a hard time
keeping his cigarettes lit when the MEA's were in the flight levels.

Rick