3 different possibilities....

[UnAnswerd]

You are suddenly at an altitude of 35,000' in a non-pressurized aircraft, and have no source of suplemental oxygen with you. Do you pass out because:

There is simply less oxygen at FL 350 as opossed to sea-level, or

There is actually the same amount of oxygen regardless of altitude, but the atmospheric pressures associated with FL 350 are responsible for greatly reducing the pressure differential between the atmosphere and the expanded diaphragm, therby decreasing the actual amount of oxygen inhailed with each breath, or

a combination of these factors. There is less oxygen at higher altitudes, and breathing efficency is also sacrifised due to lower atmospheric preasures.

 

[Cutlass1287]

The air is less dense- there is still 21% oxygen in the air, no matter where you go.

 

[Stifler's Mom]

3 different answers....

1. Hmmm, I believe it is related to their being a lower pressure at higher altitudes.

2. You should probably be more concerned with how to properly tie down an aircraft from the looks of your avatar.

...and breathing efficency is also sacrifised due to lower atmospheric preasures.

3. Go back and edit your post before Tony C gets you.

 

[uwochris]

I'd say the 2nd one.

The concentration of oxygen is the same at SL as it is at altitude (21% for a given volume). The difference is that for a given volume, there is less air at FL350 because of the lower density, and thus, you get 21% of a smaller amount.

Think of it this way. I have two 2L bottles of pop. One is full, while the other is half empty. If I give 21% of the full bottle to you, and 21% of the half-empty bottle to someone else, who has more pop? In each case, you guys get 21% of my pop (i.e. the concentration is the same).

At higher altitudes, if I compared a volume of 2 L of air at SL with 2L of air at FL350, the density of air at SL is greater- in this case, because there is "more" air, a 21% oxygen concentration is more than a 21% oxygen concentration in the latter (more air versus more pop).

Also, you have to consider the concept of "partial pressure." At FL 350, the air pressure is lower, so when you breathe in a given volume of air, the pressure may not be high enough to get the oxygen molecules transported efficiently to the cells. The lungs have to be able to extract oxygen from the air, transport it to the blood, then the blood has to transport to our body cells, and the cells have to be able to absorb it. This process is not as efficient at higher altitudes (hypoxia- and remember there are different types: hypoxic, stagnant, histoxic, and anaemic, all of which apply to the 4 requirements of blood getting to our cells).

I hope this helps.

 

[Flying Illini]

Less pressure, not less oxygen.
You don't "suck" in air, your diaphram relaxes which allows the atmospheric pressure to force the air into your lungs. Your diaphram contracts which forces the air out of your lungs, then relaxes and air is forced into your lungs...and repeat...

 

[Kingairrick]

Get a hobby.

 

[mayday1]

"Get a hobby"

someone's asking a question to try and learn something.. if you don't feel the question is a worthy one, move on.. instead of posting some stupid, condescending response.

 

[UnAnswerd]

Get a hobby.

Sorry. I should've known better than to post an honest question. What in the F*ck was I thinking....

 

[UnAnswerd]

Uwochris, I think that helps. There is technically less overall oxygen at altitude, but still the same percentage for a given volume?

 

[Daveman]

Get a hobby.

I agree. I'm surprised this "unansweird" can tie his shoe laces without asking which lace to cross first.

 

[SiuDude]

There is less oxygen at higher altitudes. There is also less nitrogen, and whatever else the air is composed of.

 

[Pilot124]

Uwochris, I think that helps. There is technically less overall oxygen at altitude, but still the same percentage for a given volume?

The oxygen ratio stays the same...21%........78% Nitrogen....1% other crap

But FEWER oxygen molecules per given volume.

answer solved...........

 

[uwochris]

Unanswered,

Pilot124 has got it. He's also got an awesome avatar!

Concentration is the same, but there's less air in the same volume.

 

[qmaster3]

Super-Dave-Man

I am appalled you would attack ones quest for knowlege..You had such class the legendary MB. Guess, it's back to waxing the ole board for Dave.

 

[Kingairrick]

"someone's asking a question to try and learn something.. if you don't feel the question is a worthy one, move on.. instead of posting some stupid, condescending response.

Lighten up, Francis...

By his original post, I assumed that unanswered was attampting to start a game show rather than ask a question he didn't know the answer to. As evidence I would point out that he posted an acceptably close to correct answer in the original post. I assumed he knew the answer and was just making conversation.

The subject is well covered in most high school science classes. Which makes the shoe tying coment appropriate as well. If one asks truly silly questions on this board, be prepared to take some heat. I have, and surely will again.

It's not meant to be "condescending", it's meant to be "blatently making fun of."

 

[Daveman]

Super-Dave-Man

I am appalled you would attack ones quest for knowlege..You had such class the legendary MB. Guess, it's back to waxing the ole board for Dave.

Ahhh, I'm just given' him helll. It goes back a few months. But you are probably right. I shouldn't have answer Unanswerd.
I will and have gone out of my way to help anyone out. Including this guy.
Until I found out his questions were not sincere. There are a few others who can back me on this.
Look at all I have posted and you might not be that appalled.

 

[mayday1]

"Lighten up, Francis" -- ah, a favorite quote, from a great movie.

sometimes I just take things at face value - i.e. accepting someone's post/question as just that... in this case, a question from someone apparently new to flying (?). I've had similar "basic" or fundamental questions, and when I'm truly looking for an answer I can usually do without the mockery.

 

[UnAnswerd]

Trust me when I say, that none of you hurt my feelings. I do however, sometimes wonder why I get responces such as those already within this thread. It seems that within this age of faceless communication, such abrasive reactions are increasingly common, despite the utmost attempts at neutralizing otherwise honest questions. Upon searching for reasons, I can unfortunatly only point to bizarre human nature, and know that such does not nessasarily exclude pilots. Although, thus far many have given me friendly answers, and for that I am truly appreciative...

So all I can say is that I'm here to learn, and willing to accept the degrading comments if only to view those that are not.

 

[EagleRJ]

#2 is the correct answer.

The key here is the 'partial pressure' present at a given altitude. At 35,000', the air is the same mixture of oxygen, nitrogen, and trace gasses, but it's just at a lower pressure.

The key to getting oxygen in your blood is the transfer of oxygen across the alveoli (sp ?), the little air sacs in your lungs. There needs to be enough pressure to push O2 molecules across the membrane into the bloodstream.
Lots of people think, "If I have a depressurization, I'll be OK for at least a couple of minutes, because I can hold my breath for that long underwater". That doesn't take into account the fact that when you are holding your breath, you have air (and oxygen) trapped in your lungs at sea-level pressure. There is still some transfer taking place until the air is completely depleted of oxygen.
When you have a depressurization, the transfer of O2 ceases instantly. If you're in the higher altitudes (40,000' and above), that means a time of useful consciousness of around seven seconds- the time that the blood that is no longer carrying oxygen takes to travel to the brain. That's the reason FARs require quick-donning O2 masks to be put on within five seconds.

If a fit, healthy person is at 35,000 without O2, they might actually be able to function for a while, with just a slow onset of hypoxia. Remember that people have climbed Mt. Everest (29,000' and change) without oxygen. Sitting in your seat has a much lower oxygen demand than climbing a mountain, even for someone who isn't as fit or acclimated to high altitudes.

 

[FN FAL]

Trust me when I say, that none of you hurt my feelings. I do however, sometimes wonder why I get responces such as those already within this thread. It seems that within this age of faceless communication, such abrasive reactions are increasingly common, despite the utmost attempts at neutralizing otherwise honest questions. Upon searching for reasons, I can unfortunatly only point to bizarre human nature, and know that such does not nessasarily exclude pilots. Although, thus far many have given me friendly answers, and for that I am truly appreciative...

So all I can say is that I'm here to learn, and willing to accept the degrading comments if only to view those that are not.

At 35,000 feet...try holding your breath after decompression. It won't help you...no matter what the theorists say...you will expell all the gasses in your lungs until the pressure equilizes.

It is then that you'll realize why nobody uses a snorkel that is ten feet long.

 

[Daveman]

At 35,000 feet...try holding your breath after decompression. It won't help you...no matter what the theorists say...you will expell all the gasses in your lungs until the pressure equilizes.

It is then that you'll realize why nobody uses a snorkel that is ten feet long.

Or the bell chamber.

 

[qmaster3]

Daveman

After further research.....I saw the light. A public Apology is in order, and the healing must begin

Good luck with that mug shot.

 

[Dizel8]

The composition of the atmospehere remain the same, well at least where we are flying, however the pressure decreases with increase in altitude.

What you are worried about, IIRC, is the fact that it takes pressure to force O2 into your lungs, actually through the cell walls of the lungs, but I digress. Since less partial pressure at altitude, your system will receive less oxygen. Up to a point, we can mitigate this by using 100% O2, however, eventually the pressure differential becomes so small, that even 100% will not help. That is why at higher altitudes, 02 is pressure fed into your system.

If we get high enough, we start running into the same problems divers do, namely the bends, in the case of rapid decompression, hence the reason for full pressure suits as worn in the U-2.

(Just saw it: Or what EagleRJ said.)

 

[Eagleflip]

And, to add on to Dizel8's reply (and fabulous avatar...), due to the partial pressure issue already well documented on these responses, it requires pressure from the mask into your lungs to allow oxygen saturation within the aveoli.

Purely sucking on oxygen, or even an air mixture, would not suffice. Positive pressure is required at any altitude above 18 thousand.

 

[learflyer]

Forget all that. HTF are you "suddenly at FL350"? Just stop the climb at 10000 and u will have no problems!!

 

[TurboS7]

Take a deep breath and hold it as long as you can.

 

[TurboS7]

You will maintain conciousness about 30 seconds unless you have portable pressure breathing equipment.

 

[TurboS7]

I was on a test flight as a first officer once and we lost the cabin at 31000 feet. We were testing a bleed valve and it failed.The cabin went through 23000 feet and climbing. I got my mask on as the warning went off the captain and FE got mezmorized with the situation and didn't get their mask on in time. I had to help them get their mask on, it was funny because once they started getting the O2 they jumped like they had just woke up. We need O2 and we won't live long without it. We need to save trees and all that good stuff.

 

[TonyC]

Forget all that. HTF are you "suddenly at FL350"? Just stop the climb at 10000 and u will have no problems!!

The same way he was able to take his girlfriend flying and scare her before he even learned to taxi or even how to turn an airplane in flight.








.

 

[Guitar Guy]

I'm wondering why you'd be at FL350 without supplemental O2.