Talk:Scuba gas planning

Choice of breathing gas
There really is very little debate about the narcotic properties of oxygen and the issue was largely settled years ago. Have a look at Nitrogen narcosis where the references are pretty copper-bottomed. Bennett & Elliot surveys the topic and finds that the relationship is complex because oxygen is metabolised and the partial pressure of oxygen in tissues varies. On page 304 (5th Ed) they report that subjects breathing 96% N2 4% O2 at 91 metres were more affected than those breathing air. (But I'd be so far out of my brain at that depth I'm amazed they were able to test anything.) Then they state: "However, reduction of the oxygen partial pressure at a constant nitrogen partial pressure does decrease the narcosis."

If you want a non-medical reference, there's the NOAA Diving Manual (2002 [16.3.1.2.4]): "since oxygen has some narcotic properties, it is appropriate to include the oxygen in the END calculation when using trimixes (Lambersten et al. 1977,1978). The non-helium portion (i.e., the sum of the oxygen and the nitrogen) is to be regarded as having the same narcotic potency as an equivalent partial pressure of nitrogen in air, regardless of the proportions of oxygen and nitrogen."

If you redo your calculation assuming the non-helium fraction has the same narcotic properties as air, then you get a more conservative estimate of the equivalent narcotic depth. It should be obvious that in these cases, the more conservative method will be preferred.


 * I had heard something to that effect, but no idea where it came from, Thanks for the refs. Will put something together to this effect, or if you have the inclination go ahead. As you will have noticed, the article is badly underreferenced so far. Unfortunately substantial referencing during composition tends to slow me down a lot, so I end up having to do it after the fact, and if anyone else knows of good refs for any of the material I would appreciate the additions. After all, with luck some might be new to me. I have a NOAA manual, but not B&E. Peter (Southwood) (talk): 05:24, 14 November 2011 (UTC)


 * It's rather more complex than your re-write suggests :D If you have a look at some of the primary studies that B&E examined you can see that sometimes O2 appears more narcotic than N2 as well as sometimes less. As a concrete example, Hesser, Fagraeus & Adolfson (1978) found that "A rise in O2 pressure to 1.65 ATA, or in N2 pressure to 6.3 ATA at a constant high PO2 level, caused a significant decrement of 10percent in mental function but no consistent effect on psychomotor function." That's a key result in our understanding of narcosis, mainly for its differentiation in the effects of air vs CO2, but also because it shows O2 seeming to display a greater narcotic effect than N2. Its quite understandable that as the fraction of O2 metabolised varies, the amount available to affect the nerve membranes changes. We have guidance from WP:MEDRS that we should prefer secondary (review) sources over primary ones for medical claims, so I think it would be better to accept the 2002 NOAA advice and say that we treat O2 and N2 as equally narcotic for gas calculation purposes. B&E does say oxygen is narcotic, but doesn't conclude that it's less narcotic than oxygen, and we shouldn't be drawing that conclusion (particularly based only on a primary study).
 * I've done the revised calculation for a 50 metre dive for you to compare - as you can see it's noticeably more conservative, but much simpler to perform. --RexxS (talk) 14:39, 14 November 2011 (UTC)


 * I forgot to add, a useful side-effect of this method of calculation is that the ratio of N2 to O2 in the trimix depends solely on the chosen END, not the depth. If you're willing to accept an END of 32 metres (and save a few coppers) then you calculate the desired FO2 as usual, then take twice that for the FN2, the rest is helium. It's simple enough to do in your head if you just want a rough idea of what your mix will look like - e.g. dive to 110 metres -> FO2 = 1.4/12 = ~12%; so FN2 = 24% and FHe = 64%
 * Also it means that if you have a source of premixed EAN32 (fairly common these days), you can knock up a trimix by blending that with He - you always get a mix with an END of 34 metres. It also means you can do the analysing by using just an O2 analyser - sometimes handy to know. --RexxS (talk) 15:08, 14 November 2011 (UTC)


 * Thanks, thats a rather interesting result (the mix with 32%). Also thanks for the pointer on WP:MEDRS.
 * I see you have laid out your example differently (format). I think we should standardise style where possible. Is there a MoS preference? Peter (Southwood) (talk): 19:24, 14 November 2011 (UTC)
 * No, there's no MoS preference (other than using wiki-markup in preference to html). I'd say get the content and references into place first, then start worrying about making a standardised look. It's usually pretty easy to do that when you have a near-finished product - and don't forget that anybody else can come along and add stuff in their own style in the meantime. Polish it later :p
 * I'd recommend looking at:
 * The references in Heliox
 * The references in Trimix (breathing gas)
 * The references in Helium
 * The other references in Nitrogen narcosis
 * The Engineering Toolbox
 * The Physics Hypertextbook
 * as you'll find values, examples, and references for most of the stuff you're adding at present. --RexxS (talk) 21:35, 14 November 2011 (UTC)
 * as you'll find values, examples, and references for most of the stuff you're adding at present. --RexxS (talk) 21:35, 14 November 2011 (UTC)


 * I have started on filling in references and links using your suggestions and others (good old NOAA and USN diving manuals) Peter (Southwood) (talk): 10:32, 15 November 2011 (UTC)

What about the American system?
Everything so far is metric. The differences in the American/Imperial system are so fundamental I dont know how best to accommodate them, and sometime it will have to be done. Two ways seem possible. I am not sure which one is most likely to cause confusion in the long run. Any thoughts? Peter (Southwood) (talk): 10:32, 15 November 2011 (UTC)
 * 1) Two entirely separate articles: Scuba gas planning (metric) and Scuba gas planning (American) or whatever name fits best.
 * 2) Two calculation sections in this article, each of which contains all calculations for the relevant system.
 * The work is great, Peter, and remember this is a wiki: you don't have to do all of the content possible; somebody else will step in and build on what you've done. When I learned to dive, we still used Imperial measures here in the UK and I went through the change to metric, so I'm fairly adept at providing conversions between the systems (I was a Maths teacher at the time). If you'd like I can do the Imperial calculations when you're ready.
 * I'd say that a parallel article is a non-starter as they would inevitably be merged together. Wikipedians don't like two articles on the same subject. Nevertheless, judicious use of sub-sections with (metric) or (Imperial) qualifiers would allow a reader to skip the sections that they had no interest in. --RexxS (talk) 15:08, 15 November 2011 (UTC)
 * That sounds reasonable. I am moderately familiar with the Imperial system in general, even the American variants, as many of my engineering texbooks used it in the 70's, but I have never used it for diving, so although I can follow the process with confidence, I am not sufficiently familiar with it to explain what it actually is. Do you have any suggestions as to how the layout should be adapted to include the alternatives? And by all means pitch in with whatever input you think will improve the article, it has reached a stage where I am running out of ideas. I am altogether too familiar with subject matter that no-one else wants to touch over on Wikitravel, but there we are encouraged to produce "original research" as that is the lifeblood of a travel directory. Peter (Southwood) (talk): 17:13, 15 November 2011 (UTC)

B-Class review
All good, promoting to B-class &bull; &bull; &bull; Peter (Southwood) (talk): 06:54, 3 January 2017 (UTC)

"Travel" gas??
From the list in the opening paragraph:

"Estimation of gas required for the planned dive, including bottom gas, travel gas, and decompression gases, as appropriate to the profile."

Bottom gas? Travel gas? Some definitions needed, I think. "Travel" gas is sort of explained by context much later in the article, but the definition really should be with the first ocurance of the term.

Orphaned references in Scuba gas planning
I check pages listed in Category:Pages with incorrect ref formatting to try to fix reference errors. One of the things I do is look for content for orphaned references in wikilinked articles. I have found content for some of Scuba gas planning's orphans, the problem is that I found more than one version. I can't determine which (if any) is correct for this article, so I am asking for a sentient editor to look it over and copy the correct ref content into this article.

Reference named "Bozanic1997": From Rule of thirds (diving):  From Diving cylinder:  

I apologize if any of the above are effectively identical; I am just a simple computer program, so I can't determine whether minor differences are significant or not. AnomieBOT ⚡ 10:18, 10 July 2022 (UTC)
 * Fixed &middot; &middot; &middot; Peter Southwood (talk): 20:29, 12 July 2022 (UTC)