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Darwin Teague

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Why is inhaling argon a bad idea?
« on: 10/07/2008 21:59:19 »
Darwin Teague asked the Naked Scientists:

I heard you discussing helium and other gases and their effects on one's voice on a recent show. I had never heard of the gases you mentioned, but I've heard that argon gas works - it lowers one's voice. You failed to mention something that is pretty important.

If one inhales these heavier gases, the only way to get them out of your lungs is to hang upside down. Otherwise some of the gas will stay trapped in the bottom of your lungs. Thanks for your great show.

What do you think?


 

Offline JonBoy

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Why is inhaling argon a bad idea?
« Reply #1 on: 13/07/2008 09:44:26 »
if you breathed then wouldent the gases would come out the same as any other gas
 

Offline Bored chemist

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Why is inhaling argon a bad idea?
« Reply #2 on: 13/07/2008 09:56:11 »
About 1% of the gas I have been inhaling since the day I was born is argon.It doesn't seem to have done me any harm.
As JonBoy says, the argon is expelled from your lungs just the same as the other gases. One of the fundamental properties of gases is that they are miscible.
Breathing pure argon is risky because there's no oxygen in it and you need oxygen to survive, on the other hand most of us can hold our breath for a minute or so- much longer than you need to demonstrate the efects of argon or helium on your voice.
 

lyner

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Why is inhaling argon a bad idea?
« Reply #3 on: 13/07/2008 13:23:45 »
Mild Hypoxia isn't a serious problem as long as there is someone around to make you start breathing  'pure' air once you start acting daft.
You would probably need quite a rich mixture of Argon to get the effect of significant voice lowering.
 

Offline jmmnq5

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Why is inhaling argon a bad idea?
« Reply #4 on: 02/11/2011 19:54:08 »
It is safe to breath argon in the atmosphere because it is thoroughly dissolved in the rest of the air, lowering it's density. If you breath argon in any concentration it can be difficult to impossible to inhale it on your own. In this case, it is NOT a matter of mild Hypoxia. You can DIE IN A MATTER OF SECONDS!!!! It is not an issue of someone helping you because they will not have time! I work in steel mills where argon is used extensively and many of them have had workers just fall over dead before anyone knew what was happening because argon, which is COLORLESS AND SCENTLESS, had filled an area. Even a single breathful of concentrated argon can be fatal. NEVER BREATH PURE ARGON!!!! And don't say that you'll be fine because you can hold your breath for a minute or more. You can hold your breath because it takes about that long to deplete the air you inhaled of oxygen (you don't use all of it in a single typical breath), but if you are breathing argon, there is no oxygen to deplete! It takes a few seconds without oxygen to be fatal!
 

Offline Bored chemist

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Why is inhaling argon a bad idea?
« Reply #5 on: 02/11/2011 20:57:09 »
jmmnq5.
Everything you say about argon is just as true for helium.
Yet practically everyone has heard the "squeaky voice" effect of breathing helium.
Essentially everyone who tries that survives.
Breathing argon is no more risky than breathing helium.
There is a risk, but it's a small risk, roughly the same as letting off fireworks.

On the other hand, I agree that people die from entering areas where there is no oxygen because it has been displaced by argon or nitrogen.
People think "I will be OK- I'm just going in for a few seconds".
In some cases that's the last thing they think.
These non toxic gases probably kill more people in a year than the toxic ones like chlorine etc.

 

Offline damocles

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Why is inhaling argon a bad idea?
« Reply #6 on: 02/11/2011 22:17:06 »
jmmnq5.
Everything you say about argon is just as true for helium.
Yet practically everyone has heard the "squeaky voice" effect of breathing helium.
Essentially everyone who tries that survives.
Breathing argon is no more risky than breathing helium.
...(snip)...

Argon is more dangerous than helium. I have no experience of working directly with argon in this way, so do not know whether the difference is trivial or major. In theory, the following points could be important:
  • Argon is heavier than air, and its atoms move more sluggishly than nitrogen or oxygen molecules. It might take very deep and vigourous breathing to remix it thoroughly into exhaled air, and prevent it from pooling at the bottom of the lungs
  • Argon is more soluble in body fluids than helium is. It is quite likely that it might act as an anaesthetic.
    http://www.general-anaesthesia.com/noblegas-anaesthesia.html

However the MSDS for argon (easily located with google) do not mention this latter effect.
 

Offline Bored chemist

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Why is inhaling argon a bad idea?
« Reply #7 on: 03/11/2011 06:54:30 »
If gases pooled in the way you suggest then we would have already drowned in the argon present in the air.
Why,even after having it pointed out that gases mix, do people not believe this?

Xenon is occasionally used as an anaesthetic.
Argon is vastly cheaper; if it worked they wouldn't use Xenon. Even krypton ( which is cheaper than xenon doesn't work.
 

Offline CliffordK

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Why is inhaling argon a bad idea?
« Reply #8 on: 03/11/2011 08:00:25 »
I think your seconds and minutes are off.  As Bored Chemist stated, most people can hold their breath for a minute or so.  It takes several minutes of anoxia to cause death.

One's typical respiratory rate is about 10 to 20 breaths per minute (at rest).  One or two breaths would be sufficient to rid one's lungs from 100% Argon.

And, the heart will continue beating, and one will continue breathing for several minutes, even if one passes out.

There have been studies with "Argox" which can be mixes of about half oxygen, half argon, although not frequently used, one can safely breathe it for a while.

All that being said, there is a difference between breathing a gas like helium or argon from a balloon and breathing it in a confined space. 

If one is overcome by fumes in a confined space, then one collapses.  One continues breathing and the heart keeps pumping, but no oxygen is available, and one eventually dies.  The rescuing person can also be overcome by fumes, and have the same thing happen to them.

If you are breathing the gas from a balloon and collapse, the balloon will go Pfffft...  and you get good clean air, and you will eventually recover unless there is an underlying heart condition which could have also caused problems with swimming under water or....

As far as hanging upside down like a monkey.
Air is typically about 1% Argon with no ill effects, and no trapping in the lungs.
The molecular weight of N2 is about 28, O2 about 32, and Argon about 40.  They are close enough that they will mix, even in the lungs.

Somewhere around 70% of the air in the lungs is expelled with each breath, and about 30% is left, mostly in the airways.  That seems higher than I thought.  But, within a few breaths, the argon would be diluted, and exhaled. 

The other thing mentioned is that argon may enter the blood (which is also true about the 1% argon naturally in the air).  There is a difference between argon and carbon monoxide.  Even if dissolved in the blood, the argon doesn't interfere with the oxygen/carbon dioxide transport in the body.  Carbon monoxide binds to the hemoglobin better than oxygen, and causes long lasting effects beyond the period of time that one is exposed to the gas.  Carbon monoxide exposure might require treatment with 100% oxygen in a hyperbaric chamber for an extended period of time.  Argon will naturally diffuse out of the body quickly. 

Now, if you are exposed to argon or nitrogen under pressure (diving), then more than normal will dissolve in the blood, and you run risk of bubbles developing in the blood if the pressure is reduced.  This is not possible if exposed to 100% argon or nitrogen at ambient pressure.  And, thus decompression would not be required.

There is discussion Argon Narcosis (similar to Nitrogen Narcosis).  But, I believe that it will only cause the narcosis effect if delivered under pressure for an extended period of time.  Again, with a few breaths of argon being insufficient to cause argon narcosis.
 

Offline damocles

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Why is inhaling argon a bad idea?
« Reply #9 on: 03/11/2011 11:59:22 »
If gases pooled in the way you suggest then we would have already drowned in the argon present in the air.
Why,even after having it pointed out that gases mix, do people not believe this?

Xenon is occasionally used as an anaesthetic.
Argon is vastly cheaper; if it worked they wouldn't use Xenon. Even krypton ( which is cheaper than xenon doesn't work.

Sorry, BC -- not sure what way you think i am suggesting. Gases do pool in the sense that if you release a pure heavy gas into air, it will immediately form a layer across the floor, or the bottom of a vessel, or whatever. Gases diffuse into one another only relatively slowly. The important thing about mixing is that gases, once mixed, do not unmix. SO if you breathe pure argon it will indeed pool at the bottom of your lungs. Vigorous breathing will mix it and allow it to be exhaled.

The pooling effect is important -- radon gas can accumulate in basements, or along creek beds in uranium rich parts of Northern Australia. It is important not to camp in certain dry creek beds.

Some air conditioning service people claimed that CFCs do not get to the stratosphere because they are heavier than air. When told that gases mix, they thought it was rubbish because they had seen the CFCs pool in the pan that they used when conditioning an automotive air conditioner.
 

Offline Bored chemist

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Why is inhaling argon a bad idea?
« Reply #10 on: 03/11/2011 18:39:16 »
Meanwhile, back in reality, we are perfectly capable of exhaling CO2 which is even denser than argon.
 

Offline damocles

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Why is inhaling argon a bad idea?
« Reply #11 on: 03/11/2011 20:25:28 »
... provided that the CO2 is in a mix of about 75% nitrogen, 15% oxygen, 5% water vapour and 5% CO2. 100% CO2 is a different matter!
 

Offline CliffordK

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Why is inhaling argon a bad idea?
« Reply #12 on: 03/11/2011 20:39:17 »
There is an official OSHA/NIOSH category for a "Confined Space".  It is a serious issue.  If one is welding inside of a tank, for example, there would be a potential risk of displacing oxygen with Argon.

One should have someone monitoring the workers in the tank.  Have an extraction plan, and also monitor for both oxygen levels and volatile compound levels.  It is unlikely that one would need to monitor Argon levels as the risk factors would be lack of oxygen, or volatile compounds, depending on the situation.

As far as high CO2 levels.  The acute risk is anoxia, which can be treated with providing fresh air, or oxygen.  There is also a chronic risk of ambient CO2 levels above 5-10% which could lead to blood acidification, difficulty exhaling, headaches, and a host of other problems, again reversed by providing fresh air.  In fact, it is likely that one could tolerate a much higher Argon percentage than a CO2 percentage in the air.
 

Offline Bored chemist

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Why is inhaling argon a bad idea?
« Reply #13 on: 04/11/2011 07:25:34 »
Damocles, you can keep ignoring reality if you like.
Lungs are built to be good at gas exchange.
The body has oxygen reserves that will tide it over for a minute or so.
Finally, here's a video of a bloke inhaling SF6 which is a lot denser than argon. (Note that you can tell he's not hanging upside down.
Even a few breaths are OK
http://www.youtube.com/watch?NR=1&v=XzT2Xqp1Q5Y
So, no matter how often you say that this is impossible, you will still  be wrong.
 

Offline damocles

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Why is inhaling argon a bad idea?
« Reply #14 on: 04/11/2011 08:20:50 »
Bored Chemist I would like you to reread my posts to this thread carefully -- nowhere do I say that gases will not mix or that anything is impossible. I certainly do not say that breathing argon is impossible -- what I am saying is that it is more hazardous than breathing helium. I also have said that I simply do not know (in practical terms) whether it is trivially or seriously more hazardous.

In my second post I say that gases pool before they mix, and that mixing can be quite a slow process. I also say that gases heavier than air will pool in your lungs. That will mean that there will be a tendency for them to be retained in your lungs in higher concentration than in your exhaled air, and that it will take more breathing to get rid of them -- whether that is a matter of one vigorous breath, or several, or a few minutes I know not, and do not claim to know. But the fact that gases pool before mixing is undeniable.

(video wars: http://www.youtube.com/watch?v=ad1KuQlu4Fk)

I think that if your SF6 breathing film star had tried to run a 400 m event immediately after the take he might have noticed a decline from his usual performance.

In my third post I point out that normal exhaled air is a mixture that is richer in carbon dioxide and water vapour and poorer in oxygen than normal air, but that its composition is not so very different and that it is certainly not the same as "exhaling CO2 which is even denser than argon".

Finally a link to a "factsheet" describing a catastrophe that occurred simply because flow and pooling of gases is much faster than intermixing of gases. There is plenty of carbon dioxide in the atmosphere (and even more argon) that could easily kill us all if it sank to the bottom. Once mixed, it stays well mixed. But until it mixes, it pools.

http://www.co2crc.com.au/dls/factsheets/CO2CRC_FactSheet_09.pdf
« Last Edit: 04/11/2011 08:23:57 by damocles »
 

Offline Bored chemist

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Why is inhaling argon a bad idea?
« Reply #15 on: 04/11/2011 11:00:08 »
"In my second post I say that gases pool before they mix,"
But we are talking about lungs where this doesn't happen.

There seem to be a number of posts here that muddle up localised high concentrations of gas that people walk into unaware and die and huffing a balloon full of argon. One of them will kill you, the other won't.

They really are not the same thing.

What I am saying, and have been all along is that the OP is simply flat out wrong.
This bit "If one inhales these heavier gases, the only way to get them out of your lungs is to hang upside down. Otherwise some of the gas will stay trapped in the bottom of your lungs. "
simply isn't true. Gases mix, in particular they mix in lungs because lungs are designed to be good at gas exchange.


You told me to read what you said and I did.
You said "Argon is heavier than air, and its atoms move more sluggishly than nitrogen or oxygen molecules. It might take very deep and vigourous breathing to remix it thoroughly into exhaled air, and prevent it from pooling at the bottom of the lungs"

OK, so argon atoms are a bit heavier than air molecules- about 33% heavier, not a massive difference.
"and its atoms move more sluggishly than nitrogen or oxygen molecules."
To compensate for that 33% change in mass you need to drop the velocity by about 17%
The speed of air molecules is about the speed of sound. The speed of the argon atoms will be about 83% of that. Something like 270m/s
Do you really think 600 miles an hour is "sluggish"?


You say that "Argon is more soluble in body fluids than helium is. It is quite likely that it might act as an anaesthetic. "
That was disproved for any practical purpose by Clifford's point about argox but even before you posted it you said "However the MSDS for argon (easily located with google) do not mention this latter effect".
Did it not occur to you that the reason for not noting that effect was that it doesn't actually exist?


And, just for the record,
" 100% CO2 is a different matter!"
No, it isn't. People occasionally do this after being rescued from fermentation vessels. (My dad used to work in a brewery, so I heard that it happened from time to time.)
So, what you did was show that an irrelevant thing is irrelevant. I wasn't talking about exhaled air, I was talking about CO2, that's why I said CO2.

Fundamentally, if you cannot distinguish the risk from a balloon full of argon from the risk from lake Nyos, you are not going to live very long.
 

Offline damocles

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Why is inhaling argon a bad idea?
« Reply #16 on: 04/11/2011 15:08:27 »
Quote
This is getting a bit 2-way personal, BUT
(1) I never said anything about hanging upside down, and I have certainly never believed what you have attributed to me.

(2) Pooling DOES happen in lungs. Clearly, from the experiences you describe it does not happen to nearly the same extent as it might, and chest movements might help to stir things up, but neither of those things mean that if you inhale a concentrated heavy gas you will get rid of all of it in the same breath

(3) I apologize for my misconstruction of your comment about exhaling CO2. Because you had not at that time spoken of your brewery experience, I mistakenly assumed that your reference to exhaling CO2 was talking about normal breathing.
I stand by my statement that exhaling 100% CO2 is a different matter to normal exhalation, even though neither of these might be overly difficult.

(4) On the anaesthesia point, I included a link to a scientific paper in a respectable medical journal in which this is discussed, and in fairness I pointed out that the MSDS did not mention it.

(5) My whole point in my original post was not to say that inhaling argon was necessarily hazardous -- I said in the post that I did not know. What I did say was that inhaling argon was more hazardous than inhaling helium. I stand by that, but in the same sense that crossing a quiet road is more hazardous than not crossing it. In all logic, saying that one course of action is more hazardous than another need not imply that either of them is particularly hazardous, nor that there is a great difference. You will find in my post the words: 

Quote
I have no experience of working directly with argon in this way, so do not know whether the difference is trivial or major.

(6) I am able to distinguish between the catastrophe at Lake Nyos and processes in the human lung, but there is no fundamental difference in the underlying principle. A heavy gas in concentrated form can pour, and it can settle under gravity at the bottom of a container for a considerable time before it gets mixed into the surrounding air, particularly if that air is still. It takes moderately vigourous stirring to achieve a rapid and thorough mixing. But gases do mix in all proportions, and once a gas sample has been thoroughly mixed it does not unmix and have its heavier gases separate out under gravity.

I was rather alarmed when you wrote

Quote
If gases pooled in the way you suggest then we would have already drowned in the argon present in the air.
Why,even after having it pointed out that gases mix, do people not believe this?

Heavy gases do pool. We do not drown in argon. Every reasonable and reasonably informed person believes that gases mix. There is no contradiction in the fact that we do not drown in atmospheric argon even though argon pools. In order to drown us the argon mixed into the atmosphere would have to unmix, and this is the thing that does not happen.
 

Offline Bored chemist

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Why is inhaling argon a bad idea?
« Reply #17 on: 04/11/2011 15:47:25 »
Can you prove this assertion
"Pooling DOES happen in lungs. "?

The reason I ask is that the much heavier gas Xenon, doesn't.
Here's  a link to an image of it not pooling at all.
http://www.lbl.gov/Science-Articles/Research-Review/Magazine/1997/extra1.html


Incidentally, do you realise why I thought that, when you said "Argon is more dangerous than helium. "
I thought that you meant it was actually dangerous?
Do you see how that looks to me to be at odds with the idea that " My whole point in my original post was not to say that inhaling argon was necessarily hazardous", especially since I had already pointed out that playing this game with He isn't actually safe.

And when you said " It might take very deep and vigourous breathing to remix it thoroughly into exhaled air, and prevent it from pooling at the bottom of the lungs"
 do you understand how I presumed you thought it would pool in the lungs and be difficult to exhale even though the image shows that the much heavier gas Xenon doesn't pool in the lungs and that the demos with SF6 show that even that very dense gas is exhaled without any real problem? Certainly not enough of a problem to stop people while doing it.

The stuff about rooms, fermentation vats and valleys near volcanic vents is a red herring.
The gases in lungs are well mixed (strictly speaking the part in the middle of the lung is well mixed- I'm aware of "end tidal sampling" but it's not a major effect here). Gases pool, but not in the circumstances we were talking about.

The Xe image shows that gases get pulled into the whole of the lung- otherwise it would be a useless technique.

You inhale argon from a balloon.
On the way in it mixes with the air in your lungs.
You exhale some of that mixture (with silly voice effects if you want).
You breathe in the next breath of air.
It mixes with the Ar/ Air mixture in your lungs.
You breathe it out with a less pronounced effect on the voice.
Subsequent breaths keep diluting the gas- roughly exponentially, until there's no longer enough to have a noticeable effect.
You never actually get pure Ar into the lungs.
It can't pool, because it's always being mixed in a system that is very good at mixing gases.
As soon as it enters the lungs it is mixed with air.
In order to pool it would have to unmix.
You started off by saying it would do this, then you changed tack and said that gases don't unmix.
Make up your mind.


« Last Edit: 04/11/2011 15:49:37 by Bored chemist »
 

Offline damocles

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Why is inhaling argon a bad idea?
« Reply #18 on: 04/11/2011 23:52:20 »
(1) The linked image that you show of the distribution of Xenon in the lung proves nothing without the full text of the scientific article. It is much more likely that the patient inhaled air with a trace of radioactive xenon incorporated than that s/he breathed xenon in high concentration.

(2) I know very little about anatomy or physiology, and I have to take your word for a lot of what you say about the lungs being "a system that's very good at mixing gases". But I am also aware that deep breathing techniques are important if you want to fully saturate your blood with oxygen, and that deep exhalation can get rid of carbon dioxide (which could only be residual air of exhalation mix), cut out the breathing reflex that CO2 stimulates, and cause you to faint.

(3) the carbon dioxide extinguishing the candle in a trough, or that flowing down the slopes near Lake Nyos also had to displace and do a bit of mixing with the air that was already there. Argon flowing into the lung on inhalation need do no displacement of air. The extent of pooling, if any, is a simple matter of how thoroughly the incoming gas mixes with the residual exhalation mixture air that is already present. The same underlying physical principles apply, though the extent of pooling is greatly affected and determined by the efficiency of mixing, which could be dynamic -- associated with motion in the air already present -- or static -- associated with the width and shape of the flow channels. It is not the case that if you breathe pure argon "you never actually get pure Ar into the lungs". On inhalation the gas you are breathing is moving inward and it is preceded by the gas already in your mouth and windpipe. Pure argon certainly arrives into the top of your lungs at least. The real question is of how far it gets while still in a moderately pure form. I agree with most of the rest of your characterization of the process over subsequent breaths. I have never said nor believed that argon mixed in air would unmix.

(4) And finally, I am pleased to see that you have backed away from your position that the very real pooling of gases has anything to do with the very unreal "drowning in atmospheric argon" scenario:

Quote from Bored chemist:
Quote
If gases pooled in the way you suggest then we would have already drowned in the argon present in the air.
Why,even after having it pointed out that gases mix, do people not believe this?

« Last Edit: 04/11/2011 23:56:14 by damocles »
 

Offline Bored chemist

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Why is inhaling argon a bad idea?
« Reply #19 on: 05/11/2011 02:21:08 »
Just stop being wrong.
"The linked image that you show of the distribution of Xenon in the lung proves nothing without the full text of the scientific article. It is much more likely that the patient inhaled air with a trace of radioactive xenon incorporated than that s/he breathed xenon in high concentration.
"

The radioactivity of the xenon is marginal.
This isn't radiological imaging in that sense.
According to this
http://books.google.co.uk/books?id=AqGQN1-JMuYC&pg=PA60&lpg=PA60&dq=MRI+imaging+lungs+%22xenon+concentration%22&source=bl&ots=Sx_yquoZhE&sig=D5yKEedw9A93EYqRc2FCFyyWqfw&hl=en&ei=iZu0TvfWIYSWOsWhhO8B&sa=X&oi=book_result&ct=result&resnum=5&ved=0CFAQ6AEwBA#v=onepage&q&f=false
The xenon concentration mat well be about 70%.


" I have to take your word for a lot of what you say about the lungs being "a system that's very good at mixing gases"."
You might have to take my word, but others might rely on their own observation that lungs work quite well.
To do that they have to mix gases well.

Gases mix as they enter the lungs. To pool as you said they do requires them to unmix. if they did that we would drown in the 1% of argon in the air.
I'm not the one backing down here.
You said that argon pooled in the lungs. It doesn't.
I pointed out that, if it pooled in lungs it would pool in general, notably the atmosphere.
if it did that we would all be dead.
We are not dead.
Argon doesn't unmix from the air and pool.
It doesn't unmix in general.
It doesn't unmix in lungs.
It doesn't pool in lungs.


 

Offline JP

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Why is inhaling argon a bad idea?
« Reply #20 on: 06/11/2011 00:21:17 »
Couldn't find Argon in the top few hits, but since breathing in a dense gas makes your voice sound funny, you can find tons of youtube videos of it.  Here's a couple of the more reputable ones talking about it.  They talk about it pooling in one of them, and note that a few breaths is enough to clear the lungs of Xenon, due to the fact that the lungs are quite good at mixing gasses.


feature=related
 

Offline Bored chemist

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Why is inhaling argon a bad idea?
« Reply #21 on: 06/11/2011 09:42:31 »
A guy saying that it pools is trumped by an MRI image that shows that it doesn't, even if the bloke has a PhD.
If it pooled then you would hear the effect  of that pooling.
His first bar of a Modern Major General would be normal pitch, as because he's be exhaling the air floating on top of the Xe, and then the pitch would drop as he got to the Xe.
Also, if the gases didn't  mix then the cut off of the effect would be sudden, rather thann gradual.

This "pooling in the lungs" has become a factioid.
http://en.wikipedia.org/wiki/Factoid
 

Offline damocles

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Why is inhaling argon a bad idea?
« Reply #22 on: 06/11/2011 22:39:23 »
 [:I]I must begin with an apology to bored chemist and to the forum in general. I did not read the material in the linked image properly -- confused MRI with other radiological imaging techniques.
Just stop being wrong.
"The linked image that you show of the distribution of Xenon in the lung proves nothing without the full text of the scientific article. It is much more likely that the patient inhaled air with a trace of radioactive xenon incorporated than that s/he breathed xenon in high concentration.
"


For the record, the Xe-129 isotope referred to is a stable isotope of xenon, not a radioactive one. And MRI does require quite a large sample of the atom being monitored to produce its images -- which means either high concentrations or long exposure times or both.

However, an image showing a uniform distribution of xenon in a lung, presented without a good amount of background detail, is not evidence that xenon does not pool. Before bored chemist has a fit of apoplexy I will stress here that I am talking here about the evidential value of these images, not the issue of pooling of itself.
It has no evidential value because, whether efficient mixing occurs or not, an "inhaled" gas will reach a steady state of uniform distribution in any container after several "breaths" if any mixing at all occurs. This can refer (again for the sake of bc's blood pressure) to an open cylinder in which a piston is raised and lowered to take in 70% of new gas on each stroke.

According to this
http://books.google.co.uk/books?id=AqGQN1-JMuYC&pg=PA60&lpg=PA60&dq=MRI+imaging+lungs+%22xenon+concentration%22&source=bl&ots=Sx_yquoZhE&sig=D5yKEedw9A93EYqRc2FCFyyWqfw&hl=en&ei=iZu0TvfWIYSWOsWhhO8B&sa=X&oi=book_result&ct=result&resnum=5&ved=0CFAQ6AEwBA#v=onepage&q&f=false
The xenon concentration mat well be about 70%.


I genuinely thank Bored chemist for providing this link, because it fills in a lot of the background information about the technique that was used to provide the image in question. In fact it gives everything except the specific details of the conditions under which the particular images were obtained -- the important ones being
(1) actual gas composition used
(2) exposure time of patient to xenon gas mix (or number of breaths)
(3) image exposure time, i.e. started immediately patient was exposed to xenon or after a few breaths; concluded immediately normal air breathing resumed or after a few breaths.
Here I mean important in considering the image as evidence of thorough mixing, not clinically important.

To very briefly summarize the linked material on these issues: Patient exposure appears to be tens of breaths. The gas mix is limited by a protocol of less than 70% xenon (to avoid possible narcosis/anaesthesia) and at least 20% oxygen (to ensure continuance of normal respiration).

The nature of the MRI technique suggests that xenon content and number of breaths were unlikely to be far below these levels.

Gases mix as they enter the lungs. To pool as you said they do requires them to unmix. if they did that we would drown in the 1% of argon in the air.
I'm not the one backing down here.
You said that argon pooled in the lungs. It doesn't.
I pointed out that, if it pooled in lungs it would pool in general, notably the atmosphere.
if it did that we would all be dead.
We are not dead.
Argon doesn't unmix from the air and pool.
It doesn't unmix in general.
It doesn't unmix in lungs.
It doesn't pool in lungs.


This summary shows an attitude of "black and white" to pooling and mixing. They are not switches, they are matters of degree. Both are very real facts about the behaviour of gases, and each is seen in many context.

Gases mix thoroughly and in all proportions. There is only ever one gas phase. Gases do not unmix. The fact that the diverse mixture of gases in air do not layer out under gravity is clear evidence of this.

but

Gases also pool. Lake Nyos and the various demonstrations of carbon dioxide flowing to extinguish candles are clear evidence of this. A heavier gas (or gas mix), on introduction to a lighter gas (or gas mix), will move downward under gravity and make pools in low lying vessels or hollows.

The extent and duration of pooling (which is not a yes/no switch) is governed by the efficiency of mixing in the environment/context that the heavy gas encounters.

Gases mix in the lungs.
They clearly do not mix much on entry because they are in a strong inward flow, in the wake of whatever gases are already present in mouth and windpipe. How efficient is the mixing once they have already reached the lungs? 50%? 90%? 99%?

Pooling (a real effect with major implications in many contexts) has nothing to do with unmixing (which never happens at near-atmospheric pressure).

The rest is a "yes it is/no it isn't argument". The point I was trying, and failing, to make is that pooling is a real effect governed by real physical laws, and as such it must occur in the lungs as in any other context. Apparently the extent of pooling is very small, trivially small even, due to the efficiency of lungs as gas mixers.

This will be my last post to this thread, as I am sure that bc will want to have the last word, and we are already generating more heat than light.
 

Offline Bored chemist

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Why is inhaling argon a bad idea?
« Reply #23 on: 07/11/2011 06:55:46 »
Well, I guess I will let you have the last word, and it's this sentence concerning the pooling of gases in the lungs and the OP's question. We both agree that the evidence tells us that:
"Apparently the extent of pooling is very small, trivially small even, due to the efficiency of lungs as gas mixers."
 

The Naked Scientists Forum

Why is inhaling argon a bad idea?
« Reply #23 on: 07/11/2011 06:55:46 »

 

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