Air temp. VS. oxygen content | DeeperBlue.com Forums
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Air temp. VS. oxygen content

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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Jersey Jim

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Mar 21, 2002
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Does anyone have knowledge of the oxygen molecule density for a given volume of air (lungs) with varying temperature? I realize that warmer air will contain less due to expansion, but by how much. This was clearly evident to me back in the 80's when learning to fly small Cessna aircraft. The lift on the wings was far better in the winter. I have been training all winter by trail running in the woods, in 30-50F temps. With the first run in the 70's, it was a difficult run trying to make the same time. Is there a formula for temp/density ratio? Particularly with hard numbers for various temps. As most of my diving is in warmer air, I see this as a major disadvantage over colder air. (But maybe offset by less body heat loss in the water).
Thanks in advance,
Jim in S. Jersey
 

thin_air

Alphabet
Sep 15, 2001
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well i think we can use the general gas law to figure this out...

(p(v))/t = (P(V))/T

where
p= pressure 1
v= volume 1 (in liters)
t= temperature 1 (kelvins)
these are in the first conditions...

P= pressure 2
V= Volume 2 (in liters)
T= Temperature 2 (kelvins)

all temperatures are in degrees kelvin (degree celcius plus 273)
all pressure in absolute pressure (gauge pressure plus 14.7 psi)
since the pressure will remain constant we can eliminate it

v/t = V/T
10L/273 = x/300 273=0 degrees celcius 300=27 degrees celcius
10L/273 = 10.98L/300
therefore 10 liters of air at 0 Celsius is equal to 10.98L at 27 celcius


form this you can measure the amout of O2 in the air,(volume x 0.21)

so for 10 liters of air you would have 2.1liters of O2 (by volume)
and for 11 liters of air you would have 2.31 liters of O2

hope this helps..
(i also hope that my math is right...)
gotta love high school physics..
 

Longfins

Well-Known Member
Oct 28, 2001
254
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Hello Jim,

I think you brought up two separate phenomena:

1. Your training, which was easier in 30-50F range, became more difficult in the 70F range. I think that's more related to heat transfer of hot, moist air out of your body, and that the air's density change plays a more minor role. In colder air, which is also going to be drier in general, the delta T is greater to your body temperature (98F plus) and as a result waste heat is expelled from your lungs more efficiently and more cool air brought in. This increases your comfort level. So at higher temperature (and probably higher humidity), delta T is less and your body can't transfer waste heat out as well as in colder air. So the training feels tougher.

2. Your Cessna's lift is better in winter than in summer. This probably is related to the air density change, which (see below) doesn't seem to change all that much with temperature. But you've got to consider too that you're flowing thousands of liters of air per second over your wings. So the effect adds up to kilograms of lift easily.

Here are some numbers from a table for you to play (interpolate) with:

At 1 Bar atmosphere, the atmospheric density is:
T(Kelvin), Rho (g/L)
100, 3.556
200, 1.746
300, 1.161
500, 0.696

Peter S.
 
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icarus pacific

Human-in-training
Nov 7, 2001
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Originally posted by thin_air
well i think we can use the general gas law to figure this out...

(p(v))/t = (P(V))/T

where
p= pressure 1
v= volume 1 (in liters)
t= temperature 1 (kelvins)
these are in the first conditions...

P= pressure 2
V= Volume 2 (in liters)
T= Temperature 2 (kelvins)

all temperatures are in degrees kelvin (degree celcius plus 273)
all pressure in absolute pressure (gauge pressure plus 14.7 psi)
since the pressure will remain constant we can eliminate it

v/t = V/T
10L/273 = x/300 273=0 degrees celcius 300=27 degrees celcius
10L/273 = 10.98L/300
therefore 10 liters of air at 0 Celsius is equal to 10.98L at 27 celcius


form this you can measure the amout of O2 in the air,(volume x 0.21)

so for 10 liters of air you would have 2.1liters of O2 (by volume)
and for 11 liters of air you would have 2.31 liters of O2

hope this helps..
(i also hope that my math is right...)
gotta love high school physics..


jesus... this kid's 15?!

sven
 
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efattah

Well-Known Member
Mar 2, 2001
3,294
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No difference

I thought of this problem before; but, your throat & nose warm the air so fast that it enters your lungs at a high temperature anyway.

If it didn't, it would be possible to embolism by inhaling cold air to the max, then holding your breath; as the air warmed and expanded, your chest would explode. But it doesn't!


Eric Fattah
BC, Canada
 

Jersey Jim

New Member
Mar 21, 2002
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Thanks for formula

Vincent, Peter & Eric:
Thanks so much for your input on this subject. Especially Vincent for reducing that formula to one that is easy to interpret, and practical to apply. Here's how I see it now with your formula example: Assuming a diver could have 10L lungs as in your example, he would need 10.98L lungs at 27C in order to carry the same oxygen he inhaled at the 0C temp. Since his lungs are going to expand to the same capacity at either temperature, and not 10.98L that the air expanded to at the higher temp., the diver would therefore inhale 9.8% less oxygen at the warmer temperature than he did with the more condensed air at 0C. This 9.8% holds true at even a more typical lung capacity than your formula example. Say, 5L & 5.49 Liters for the 2 temp extremes. Exactly half. 0.49L/5L=0.098 This seems pretty significant if you ask me, and I wouldn't have been able to put this into perspective without your formula! That's what so great about this forum. Where else can you get such practical, expert opinions from such a collective group of knowledgable people!
Also Eric, I have not learned or practiced packing yet, but is it possible to pack an additional volume of 9.8%? I wonder what number of pack this would require. Somewhere on this forum weeks or more ago, I read someone who seemed to know the total packs of his lung capacity. That would sure be helpfull to know. I think it's fascinating how you say the nose & throat can preheat the incoming air that quickly. Do you think this is more efficient with or without a dry throat, which seems to happen from the snorkel?
Again, thanks to all for such good input.
Jim
 

Walrus

Oz freediver
Oct 3, 2001
693
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Elevation vs oxygen content

Hi All,

since some of you already got the formulae’s out I thought I might ask a similar question. What would the difference in oxygen content be at 580m (1900 ft) elevation vs sea level ?
And how much would this affect doing a static breathold ?

I live at 580m elevation and in the past I have noticed I could usually do better statics when I tried them at the coast. Now part of it could be psychological or that it was warmer etc. I realize it wouldn't be a huge difference but think it might be around 2 or 3 % ?

Anybody got any clues ?
 

Bill

Baron of Breathold
Oct 17, 2001
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PO2

A real rough 'rule of thumb' is 1% loss per 150 meters. I did some training at cruise altitude (2000-2500 meters cabin altitude) and I'm sure it's close.

Aloha
Bill
 

A Brownsword

Well-Known Member
Mar 25, 2002
102
3
108
Martin Stepanek's lung volume has been measured at 8 litres (!!), and I recall Kirk saying that with packing he could get over 10 litres (in fact half my brain keeps telling me that he said 12L, but the other half refuses to believe it). Either way that is 25+% increase due to packing.
 

efattah

Well-Known Member
Mar 2, 2001
3,294
487
173
Lung volumes

I don't always like talking about the lung volume issue because it's not as important as it seems -- air is the worst kind of energy store because of the compressibility, narcosis, and pressure on the arteries during packing. Nevertheless, I know that Hubert Maier gets 14 litres with packing; Herbert has 7L without packing, 10L with packing. I have a spirometer, and in my case the most I ever got without packing was 7.89L, and with packing, 10.55L (with packing & reverse packing I once got 10.90L). I also once tried various positions to see which one I could get the most volume:
- Lying on my back floating on the water
- Sitting on the edge of the pool
- Face down breathing through my snorkel
- Standing up

Standing up gave the most, face down with my snorkel was a surprising second, and the other two were tied at a distant fourth.

However, my friend Stephanie gets the most while lying on her back. She can get over 7.20L with packing, which is a lot for a woman.

On another interesting note, when I first got my spirometer I could only pack 9.5L, and only after lots of practice could I increase that by another litre. I can also say that stretching is extremely important; if I don't stretch I can even break 9L.

Eric
 
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thin_air

Alphabet
Sep 15, 2001
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Re: or on his knees

Originally posted by icarus pacific
Anderson get's most of his on his back too! rofl

sven

im just happy sven hasnt turned on me yet...

what do people recommend as a good way to measure lung volume....

i usually just use the displacement method... (water in a jug upside down in a sink)

ps. sven, who says 15 year olds have to be dumb
 

Bill

Baron of Breathold
Oct 17, 2001
1,805
332
188
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15

>ps. sven, who says 15 year olds have to be dumb

Vincent
Maybe he's just doing a flashback to when he was that age. Some of us were pretty dumb. At least I joined the Royal Canadian Air Force at sixteen, that wasn't dumb.

Aloha
Bill

P.S. Thanks for the help on Absolute. I couldn't remember that number
P.P.S. The jug method is accurate enough, lung volume is not that important as Eric says.
 
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A Brownsword

Well-Known Member
Mar 25, 2002
102
3
108
Re: Lung volumes

Originally posted by efattah
I don't always like talking about the lung volume issue because it's not as important as it seems -- air is the worst kind of energy store because of the compressibility, narcosis, and pressure on the arteries during packing.

Its a bit off-topic for this thread, but this is an interesting comment (which I'm quite prepared to believe), but it begs the question of what is most important and what can you do about it...?
 

Bill

Baron of Breathold
Oct 17, 2001
1,805
332
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new topic??

Andrew
Good idea. How about a new thread. 'What helps most' 'How do I get to Eric/2' or ?

Aloha
Bill
 

icarus pacific

Human-in-training
Nov 7, 2001
2,880
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All I know is, I've got a Master's in Engineering and I had to go look for that formula. And even then I didn't get it, same as when I was 15 and it was probably being taught to me then.
Of course my attentions were devoted to the blonde across the classroom... :inlove And yes, Anderson, she was a she.

sven DB's advocate for 15 yr olds.
 
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