|WikiProject Scuba diving||(Rated C-class, High-importance)|
"It was much used in frogmen's rebreathers."
This needs to be fixed with whatever the proper meaning is - commonly used? often used? once used? TheHYPO 18:04, 27 August 2007 (UTC)
"Breathing gas" seems to be a pretty generic concept - why is this article all about the term in the context of scuba diving? —Preceding unsigned comment added by 22.214.171.124 (talk) 21:36, 27 April 2009 (UTC)
Two of the three listed "essential features" of a safe breathing gas seem to be contradictory. The first implies that oxygen must be included ("it must contain sufficient oxygen...") but the third seems to imply that oxygen shouldn't be included ("it must not become toxic … high pressure ... Oxygen and nitrogen ... become toxic under pressure).
- It's called the Three Bears Effect. The first dish of porridge Goldilocks tried was too hot, the second too cold, and the third was just right. With oxygen, the human body doesn't like oxygen partial pressure less than about 0.15 bar (hypoxia), and it doesn't like oxygen above about 1.6 bar (oxygen toxicity). But the range in between is "just right". --RexxS (talk) 15:20, 2 September 2009 (UTC)
CO_2 is described as a toxin in the article & I feel that's somewhat oversimplified or inaccurate (take your pick), considering the bohr effect http://en.wikipedia.org/wiki/Bohr_effect on hemoglobin. . . I do believe that including CO_2 is avoided in most breathing gasses, it's inaccurate to say CO_2 is toxic. (One could argue that too much CO2 is indeed toxic, but the same can be said about Oxygen, Nitrogen, and even water, so that argument would be hypocritical. =) ) 126.96.36.199 (talk) 14:05, 26 December 2009 (UTC)
- Well, no. Carbon dioxide is not described as toxic in the article, other than in a reference (Christian Lambertsen's paper Carbon Dioxide Tolerance and Toxicity). The article only refers to the condition carbon dioxide poisoning (or hypercapnia). That article is also well-referenced. The effect of excess CO2 is primarily to increase breathing and heart rates, which is dangerous for a diver; the effect of decreasing the oxygen affinity of haemoglobin is minor in comparison. This article actually does mention oxygen and nitrogen as "examples of gases that become toxic under pressure". Nevertheless, we don't rely on our own opinions, we use whatever is found in reliable sources. I have no doubt that the sources are accurately reflected here. --RexxS (talk) 14:53, 26 December 2009 (UTC)
Deep Sea Creature Neuron Structure
Perhaps some insight into the specific actions of various breathing gases on the brain could be gained by examining the neurons of deep sea creatures and transient (air breathing) deep sea visitors.
What lipids are they using for their cell membranes? Are there special chemicals (like myelin in humans) that are used to assist transmission? How does the density of neuroreceptors in a synapse change with similar species living at different depths?
Pitch or timbre
With reference to Talk:Helium#Correction to Biological Effects where the consensus seems to be that helium does not alter the pitch of the voice, only its timbre. The gist of the argument is that the vocal chords will vibrate at approximately the same frequency, so the fundamental note is unaffected, although the pitch of the resonances will change in helium, which produces a shift in the relative overtones (i.e. the timbre). I suppose you could ask whether playing middle 'C' on a piano in a helium-rich atmosphere would produce a note other than middle 'C'? In my humble opinion, it wouldn't. --RexxS (talk) 17:24, 19 September 2011 (UTC): There is a description of the debate around the effect of helium on the human voice at
Carbon dioxide: asphyxiant or toxic
The edit "though more properly, carbon dioxide is an asphyxiant gas. It is relatively inert. High concentrations in breathing air--by displacing oxygen--can cause dizziness and even death through suffication." is disputed, and has been reverted. See
hypocapnia Hypercapnia. Any gas mixture is asphyxiant if it does not contain sufficient oxygen, not all of these are toxic. The asphyxiant qualities of carbon dioxide are unimportant in this context as the toxic effects manifest at order of magnitude lower concentrations. Peter (Southwood) (talk): 10:23, 17 May 2012 (UTC)
- Indeed, Peter. Carbon dioxide is anything but inert as it reacts with water to produce carbonic acid. I think you might have intended hypercapnia to describe the symptoms of breathing high concentrations of CO2, but I agree wholeheartedly that for CO2 the system described at Respiratory acidosis#Physiological response is of far more significance to the composition of a breathing gas than asphyxiation would be. --RexxS (talk) 18:47, 17 May 2012 (UTC)
- Absolutely. Replace 10% of your breathing mix with any asphyxiant gas like nitrogen, argon, even a brominated Halon, and you'll never know it. That much Halon will keep your matches from lighting and fires from burning, but you'll breathe it and feel fine. However, do that with CO2 and you're soon dead, dead, dead. SBHarris 20:42, 17 May 2012 (UTC)
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Helium - This sentence doesn't make sense
"Helium is not very suitable for dry suit inflation owing to its poor thermal insulation properties – helium is a very good conductor of heat (compared to air which is a rather poor, making it more of an insulator)."
Helium can't be "a very good conductor of heat" and an insulator at the same time. One could insert the word "not" to fix this, but I don't know enough about the topic to want to do this. Would someone knowledgeable make the needed revision. Janice Vian, Ph.D. (talk) 06:05, 18 February 2017 (UTC)
- @Janice Margaret Vian: The terms "insulator" and "conductor" for a substance only have meaning relative to another substance, as a vacuum is the only perfect insulator for thermal conductivity; everything else is a conductor to some degree. Helium is quite a good conductor relative to air or argon, but still an insulator relative to a metal like copper, or even relative to water. Here are those thermal conductivities (at 25 °C, 1 atmosphere) for comparison:
Selected thermal conductivities in milliWatts/metre-Kelvin Material Conductivity Argon 16 Air 24 Helium 142 Water 580 Copper 401,000