# Talk:Diving cylinder

12/14/06
Discussion regarding the phrase copied below:
A diving cylinder (the term which tends to be used by divers) or SCUBA tank (more often used colloquially by non-divers)
As a NOWI Certified Diver and a PADI Certified Diver for more than twenty-five years, I can attest to the fact that I have never heard an American diver or American Oceanographer refer to our "Dive Tanks" as anything other than "Tanks." Therefore, the author's statment as prefaced above in parenthesis may be not be valid.
In any case, the reference to "non-divers" seems a bit unnecessary and sounds more like personal opinion rather than an actual fact.  I recently, reviewed my old dive manuals whereby, the official terminology used here in the USA is "Tank" and not "Cylinder." The only exception I found was at a PADI web site tonight. However, I noticed the date of birth on the registration page of the website is European I.e. day/month/year as opposed to American month/day/year. Therefore,the term cylinder would be more appropriate coming from European divers. There is also a dive master video on the NOWI website regarding equipment. The term tank is being frequently used by the dive master when referring to the breathing unit.  
European divers would generally refer to them as "tanks" - the proper name being a "cylinder" however, its not used in general speaking. Perhaps non-english speakers translate as cylinder?  —Preceding unsigned comment added by 89.168.72.84 (talk) 23:05, 9 December 2007 (UTC) 
I have seen the same (idiotic) argumnet over the term skeg or fin on a surfboard and have heard some say that only a non-surfer would say skeg. I simply believe this type of commentary detracts from the article in general and is therefore, may not necessary.
PEACE
(LCrockett 04:16, 15 December 2006 (UTC))hope I did this correctly :-(?

You don't have to indent paragraphs (screws things up if you do). Otherwise you did fine.  I get three times as many Google hits on scuba tank as scuba cylinder. But I do notice that makers and engineers tend to call them cylinders. Perhaps this filters down to those who want to sound like the people who make (and service and hydrotest) the stuff, rather than just use it. SBHarris 08:23, 15 December 2006 (UTC)
Should Diving tank  be added as a redirect to this article? --ArmadilloFromHellGateBridge 08:36, 15 December 2006 (UTC)
Yes, I think so, and have done so. Along the way I fixed the definitions so that I think everyone will be happy and satisfied. "Gas cylinder" is the generic term used by engineers and the ACGA people who use all kinds of sizes of compressed gas containers, not just the ones for scuba. Even the big H cylinders get called tanks by the non-cognoscenti, but never by people who work on them for a living. The same kind of distinction carries over to scuba. SBHarris 18:27, 15 December 2006 (UTC)

"Breathing industrial compressed gases can be lethal because the high pressure increases the effect of any impurities in them.". I breath welding oxygen on a regular basis and so do a lot of other people. My research says it's the same oxygen used for both applications. Maybe that should be clarified. 142.165.246.187 16:13, 10 February 2007 (UTC)

I would wish to take issue that welding and breathing oxygen can be regarded as the same product. In the UK, USA and Europe there are both civilian and military specifications for welding oxygen and for diving quality oxygen (and medical oxygen). I would suggest that you could safely use diving oxygen and medical oxygen, if you wished, for welding but it would not be sensible to do so as these products are more expensive than welding oxygen. Likewise, you could use industrial grade oxygen (welding oxygen) for diving, however it is not sold (in the UK and Europe) as a breathing gas; and that it would be safer to use one that is sold for that purpose. Perhaps, that partially answers your point.Pyrotec 18:29, 10 February 2007 (UTC)
My anecdotal experience comes from talking to someone who worked for BOC (British Oxygen Company) some years ago. He maintained that all of the oxygen sold came from the same source, i.e. there was only one process used. The only exception being "Aviation grade" oxygen which had an extra stage of processing to remove any remaining water vapour because of the low temperatures that this oxygen may be exposed to. So medical, breathing and welding oxygen all came out of the same pipe. The catch was that BOC rented large cylinders to the end-user to hold the oxygen; when empty, these would simply be swapped for a full one. There was no procedure for ensuring that the cylinder was clean for customers who purchased welding oxygen, while the "higher" grades had the cylinders cleaned regularly. All of this seems to make commercial sense to me, so I have no reason to dispute his claims. Bottom line: you have a good chance of getting the same oxygen when breathing "welding grade", but no guarantees. RexxS (talk) 20:09, 6 January 2008 (UTC)
"The pipe bit" is not the whole story; as you say an important part of the filling process is ensuring that the cylinder is clean before it is filled. Any hospital or dive shop that "plugs" a patient or diver into a cylinder of welding grade oxygen is going to get a large legal bill if someone suffers as a consequence. If its a proper medical or diving cylinder, then BOC or its competitors carry the consequences of "dirty" product being supplied. Pyrotec (talk) 20:26, 6 January 2008 (UTC)

To calculate the quantity of gas:

 quantity of gas = volume x pressure

But:

3 litres * 200 bar = 60 kilojoules

Should the article clear this up?
Also we might want to include some mention of the energy content (compressed air) of scuba tanks. —Preceding unsigned comment added by Glueball (talk • contribs) 11:55, 12 July 2007(UTC)

The formula only works in metric units - it's just Boyle's Law (and subject to the same limitations). Should be
"Volume of gas at atmospheric pressure = (cylinder volume) x (cylinder pressure) / (atmospheric pressure)"
I'll change it. And it would be of interest to show the energy stored in a cylinder - maybe with some comparisons to TNT, etc.? RexxS (talk) 20:29, 6 January 2008 (UTC)
A liter-bar is 100 J = 0.1 kJ, giving you the energy above, but this assumes that all the volume is delivered at this pressure, which if course is not the case in a scuba tank. As it charges, or as it explodes or discharges, the pressure runs up or down as the volume is delivered, so differential work at each instant changes, and the correct formula integrates the PV work over the whole process. There are two ways to do this: one is to assume that the heat or "cold" stays in the gas during the compression/decompression (a good assumption for charging a cylinder in air (say with fill-whip on a boat), or for one that explodes). The other way is to assume that compression heat leaks out to ambient temp, as in the tank-fill water bath (which is how you figure how much extra energy is, in a tank after it has cooled back down to room temp, and assuming that you discharge the gas so slowly that it has time to absorb surrounding heat which it can convert to work.)  The work to charge a tank VERY slowly and isothermally (or discharge it over an hour where the gas can warm up in the first stage), is W = P(1)V(1)ln (P2/P1). For a typical aluminum 80 at the surface, P1 is 11.3 L, P1 is 1 bar, P2 is 200 bar, so the work is 12,000 L-bar or so, or 1.2 MJ or 1200 kJ. This is 286 Cal, or about as much as in a candy bar. But no small potatoes energy-wise if released quickly, as a stick of dynamite is only 2100 kJ. So only half a stick of dynamite. In fact, for a fast adiabatic release, as in a tank explosion, it will be even less than this, since the gas will cool as it expands and does work on the environment, and thus will not do as much work as if it had been allowed to remain at the same temperature, absorbing heat in a slow expansion. SBHarris 00:58, 20 September 2009 (UTC)
This assumes a ideal gas. Air at 200 or 300bar is NOT an ideal gas. So 10L at 300bar ends up at only about 2700L air, a full 10% shy of the teoretical 3000L! --StefanHuszics (talk) 04:42, 19 May 2010 (UTC)
That's true and it's mentioned in the article. At 232 bar, the deviation from ideal gas law linearity is about 5% (assuming temperatures around 300 K). There's an article Compressibility factor that has lots of good data. --RexxS (talk) 05:09, 19 May 2010 (UTC)

The formula and example are wrong, imho. They miss the point that ambient pressure should include the contribution of the weight of air above the water. In metric terms, you need to add 1 bar (or atmosphere - I know they're strictly not the same). The current formula leads to the conclusion that you can breathe off the cylinder for an infinite time at a depth of 0 metres! I would suggest:
AP = D * g * rho + atmospheric pressure
in proper units. However, gravity and water density are near constant compared to other variables, so this approximates to:
AP = D / 10 + 1
for all practical purposes. Remember that analogue depth gauges and analogue pressure gauges have errors both in linearity and readability, so there's little point in trying for absolute accuracy here when other variables can easily be out by 5% or more. Not forgetting of course that "depth gauges" work by measuring ambient pressure anyway, so correcting for water pressure is pointless as you really ought to correct the depth read by the same factor in the opposite direction - unless somebody has invented a dive computer that knows if it's diving in fresh or salt water. And of course, the biggest variable is breathing rate, which is difficult to keep within +/- 10% even for the most experienced divers.
Finally, there's no point in using the term (CP-AP) when CP is much greater than AP in all practical circumstances. If the purpose of this section is an illustration of how dives may be planned (rather than a sterile demonstration of how long before a cylinder becomes unusable), may I suggest that (CP-RP), where RP is the reserve pressure, would give more real-life information to the beginner and non-diver alike?
RexxS (talk) 21:40, 6 January 2008 (UTC)

I'm looking at trying to clarify the sentence "From August 2008, these shall be required for all diving equipment used with Nitrox or pure oxygen."
The word that needs clarification is required. Required for what?
EN 144-3:2003 (ISBN: 0 580 41367 5) Respiratory protective devices. Gas cylinder valves. Outlet connections for diving gases Nitrox and oxygen does not address 'requirements' and is not legislation per se. It is true that if equipment is to be CE certified from August 2008, then it must comply with this European Norm. Note, though, that it says nothing about procedures for filling cylinders or using them safely. It certainly does not make the use of M25x2 connections illegal when used for nitrox or O2.
The EN which deals with requirements is in fact, EN 13949:2003 (ISBN: 0 580 41368 3) Respiratory equipment. Open-circuit self-contained diving apparatus for use with compressed Nitrox and oxygen. Requirements, testing, marking. It is interesting to see what EN 13949:2003 says about cylinder connections:

4.4 Pressure vessel valve(s)
Pressure vessel valve(s) shall comply with appropriate national or European Regulations and shall be approved and tested for use at the rated working pressure and pure oxygen.
The threads for connecting the pressure vessel(s) and the valve(s) shall be M 18 x 1,5 or M 25 x 2 as specified in EN 144-1.
Safe connection between the pressure vessel valve(s) and the demand regulator shall be ensured by using the connections as defined in EN 144-3.

So a little bit of drafting inexactitude? Both norms published on the same date, but the latter (although mentioning EN 144-3) fails to include M26x2 threads as permissible!
--RexxS (talk) 23:13, 27 August 2008 (UTC)

Mark.murphy added the following: "To reduce the diver's high negative buoyancy when carrying many cylinders, divers often use aluminium stage cylinders because they are less dense than steel cylinders." I don't doubt that divers do that, but in most cases it's a mistake. Unless a diver has so much negative buoyancy that they have no weights, then the material of the cylinder is irrelevant: a properly weighted diver will be neutral with empty cylinders - the negative buoyancy at the start of a dive is simply the weight of air in the cylinders. All that aluminium cylinders do is increase the total volume of the diver+equipment, which means that they carry a greater total weight out of the water - not a desirable thing.
Anyway, I don't want to remove the statement, since I know that divers do use Al cylinders, mistakenly thinking that a less dense cylinder means less total negative buoyancy. But I'm concerned that the article now gives the wrong impression. This article isn't really the right place to present the arguments about buoyancy, correct weighting and choice of equipment. Is there an alternative formulation that would meet my concerns? --RexxS (talk) 15:19, 21 February 2009 (UTC)

Rexx, you are right. The explanation was not correct or complete. I have improved it.
Mark.murphy (talk) 18:11, 21 February 2009 (UTC)
Thanks Mark, you've made a good job of that - it explains well without the complexity I wanted to avoid. Cheers --RexxS (talk) 00:27, 22 February 2009 (UTC)

Although "Spare Air" is a trademark, that doesn't prevent the phrase being used in Wikipedia. Since the Spare Air is the only device of its type that I'm aware of, I'm unable to find a generic term to describe it. A "micro-aqualung" doesn't fit, since googling for that only brings up hits for the magical device used by James Bond in Thunderball or something similar used in Pokemon. I've referred to Spare Air by name and cited the website as the source. I must say that although I regard these devices as almost worthless, they exist and divers do use them, so they deserve a mention in the article. --RexxS (talk) 19:18, 19 September 2009 (UTC)

They are Bail-Out Bottles. Regardless of size.  — Preceding unsigned comment added by 71.4.236.2 (talk) 14:51, 28 June 2011 (UTC)

For an article that is 36 kilobytes in size, there is a woeful lack of referencing to reliable sources. When assessing the article on the quality scale, I had difficulty in deciding if it should be a stub or start-class. There is one undoubtedly reliable source, but that is to a study mainly concerning impurities in the breathing gas (and is more relevant to the article on compressors). If there really is such a lack of sources, then perhaps this topic is not notable enough to warrant an article? --RexxS (talk) 15:02, 22 September 2009 (UTC)

The references are out there, but editors have choosen to add material without providing citations. Pyrotec (talk) 18:44, 22 September 2009 (UTC)

These are two photographs which may add clarity and interest to the text of "Diving Cylinder".  They are my photographs of my equipment taken yesterday, 2010-07-22, and are made available to you with my blessings.  All substantiating paperwork is included in the "Gallery" with the .jpg images themselves.
As was mentioned, "J" Valves are not normally found today on modern equipment.  However "J" Valves were incorporated in the earliest SCUBA gear from the time of Jacques Yves Cousteau and Emile Gagnon original invention and were the normal reserve systems until they became obsolete when high quality diving computers incorporating tank pressure gauges made them superfluous.
John W. Goodspeed
"TheGoodspeeds
(TheGoodspeeds (talk) 17:24, 23 July 2010 (UTC))

It's generally accepted that EU regulations require a diving cylinder to have a label that describes its contents. We know this because dive shops tell us so when we take in an old cylinder for a fill or test. However, here in the UK, it's not well-known what the relevant legislation actually says about diving cylinders, not least because it's not immediately obvious what the actual regulation number is.
There's a good leaflet from the UK Health and Safety Executive (INDG308(rev1) 4/02 C250), which is free to reproduce as long as the HSE is credited. A copy can be found online at http://www.lambaydiving.com/ukhse.pdf and it summarises the regulations that apply to the manufacture, testing, filling, and transportation of gas cylinders.
The standard EN 1089 Gas Cylinder Identification sets out the EU requirements for stamp marking, precautionary labels and colour coding. There's a summary online at http://www.ukdivers.net/equipment/cylinders.htm which is usually pretty accurate, but I wouldn't feel comfortable using it as a Wikipedia reliable source. I'll take a trip to the library this week to see if I can find the wording of the actual regulation. --RexxS (talk) 17:24, 13 November 2011 (UTC)

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 Diving cylinder'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 "NOAA":
From Scuba diving: NOAA Diving Manual, 4th Edition, Best Publishing, 2001
From Scuba gas planning: National Oceanographic and Atmospheric Administration, (); NOAA Diving Manual, Fourth Edition, U.S. Department of Commerce National Technical Information Service, Springfield, VA 

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⚡ 14:05, 27 November 2011 (UTC)

Re. the following text under "Manifolded twin set/doubles with two regulators":
"The pros of this configuration include [1] a large gas supply, [2] no requirement to change regulators underwater, [3] automatic gas supply management, and [4] in most failure situations the diver may close a failed valve or isolate a cylinder in order to leave himself with an emergency supply."
Let me use "manifolds" to mean a twin tank system where the two tanks are joined by a manifold; and "independents" to mean a twin tank system where the two tanks are totally independent.

[1], as stated, is just not true as an advantage of manifolds over independents. Two tanks, manifolded, have no more total gas than the same two tanks rigged independently. I suspect the author was actually thinking of [4].
[4] is true, but doesn't actually state the critical benefit of manifolds - namely, that closing valves or isolating cyclinders generally lets you retain access to *all* the remaining gas *on both sides* - unlike independents, where a failure on one side will generally result in losing access to all the gas on the failed side.
[3] is a poor choice of words. Most technical divers would understand "gas management" as meaning a range of things, such as, choosing the right size tanks for the dive; filling them to adequate pressures; being aware of differing personal gas consumption rates for different members of the team or group; following the "rule of thirds" when entering overhead environments, and so on. None of those things are specific to manifolds. All of them are equally applicable to independents.
I suggest replacing the quoted text with something like this:
"The pros of this configuration include: automatic balancing of the gas supply between the two tanks; thus, no requirement to constantly change regulators underwater during the dive; and in most failure situations, the diver may close a failed valve or isolate a cylinder and thus retain access to all the remaining gas in both the tanks."
TC 203.122.223.123 (talk) 11:15, 26 April 2013 (UTC)

Thank you for your well reasoned and constructive comment. It has been used in the article almost as stated. The advantage of a larger gas supply is valid when compared with a single cylinder (in most cases) and has been changed to specify that point. Gas management would include the balancing of available gas during a dive, but your version is unambiguous and an improvement on the original text. Please feel welcome to make further comments on any of the diving articles, and when you have an improvement which is unlikely to be controversial, you are free to edit the article yourself. It will be checked, and may be modified again, that is how this wiki works. Cheers, • • • Peter (Southwood) (talk): 16:45, 26 April 2013 (UTC)

132.3.29.79 posted this comment on 1 August 2013 (view all feedback).

The web page could benifit from US equivalent information, as it caters to metric users. While the Aluminim 80 is mentioned almost as an afterthought, common tank sizes such as a steel 100 and steel 120 are completely missing. Also missing is a discusion of low pressure vs high pressure steel tanks.
This is a good point. Any volunteers? This equipment is not used much in my part of the world. Alternatively point me at a good reference. • • • Peter (Southwood) (talk): 09:11, 17 August 2013 (UTC)

Found some refs and added some content. Any comments? • • • Peter (Southwood) (talk): 16:12, 17 August 2013 (UTC)

The list gives the impression that these are the same for every cylinder of this type. This is frankly not correct. I have several sets of 12l tanks weighing ~14kgs. 
They generally seem to be about two KGs too heavy. Maybe this can be reworded to make clear that this is an example, because the general message is still true.
But overall, I do not see why there even needs to be this full table. I think it might suffice to say that 1L of tank volume at 200 Bars corresponds to ~250 grams of air, and maybe show the common 10/12/AL80s in comparison. --Data2 (talk) 13:10, 8 February 2015 (UTC)

The article meets the six B-Class criteria:

The article is suitably referenced, with inline citations. It has reliable sources, and any important or controversial material which is likely to be challenged is cited.
The article reasonably covers the topic, and does not contain obvious omissions or inaccuracies. It contains a large proportion of the material necessary for an A-Class article.
The article has a defined structure. Content is organized into groups of related material, including a lead section and all the sections that can reasonably be included in an article of its kind.
The article is reasonably well-written. The prose contains no major grammatical errors and flows sensibly.
The article contains supporting materials where appropriate. Illustrations are adequate. Diagrams and an infobox etc. are included where they are relevant and useful to the content.
The article presents its content in an appropriately understandable way. It is written with a broad audience in mind. The article does not assume unnecessary technical background and technical terms are explained.
If anyone disagrees, please specify where it falls short, so it can be fixed. 
Suggestions for upgrade to A-class are welcome. It is probably pretty close already.
• • • Peter (Southwood) (talk): 10:04, 5 June 2015 (UTC)

Thanks, Peter. We don't have A-class criteria for WikiProject Scuba - only the big projects like Military History have the resources to undertake rigorous reviews like that. However, it would certainly be a good experience for you to look at taking this article through the Good Article Nomination process - the six Wikipedia:Good article criteria are not too different from the B-class criteria, but you have an external reviewer who makes the final judgement. It's a fast way to iron out the minor wrinkles that may be present and helps maintain consistency of quality across different topics in Wikipedia. Having been through it a few times myself, I'd be more than happy to lend a hand if you decide to go down that route. --RexxS (talk) 16:54, 5 June 2015 (UTC)
Thanks, I will give it a go. • • • Peter (Southwood) (talk): 20:26, 5 June 2015 (UTC)
There are a few outstanding citations, some for things for which I have no references, but are probably true and uncontroversial, just uncited. How do we deal with this? • • • Peter (Southwood) (talk): 15:15, 6 June 2015 (UTC)
Ask Gene Hobbs, of course! If sources exist, I'm willing to bet that Gene knows where to find them. If he can't find sources, take out the cn tags that you placed for anything you think is uncontroversial. Should facts then be challenged at GA review, the correct action would be to remove the text (and put it on the talk page, pending sources being found). Take a look at the three GA reviews at Talk:Oxygen toxicity/Archive 1 and you'll get some idea of the process of refinement that a review provides for the article (and how valuable it is to have Gene as a collaborator). What I learned there allowed me to take the oxygen toxicity article to Featured Article status soon after. --RexxS (talk) 15:50, 6 June 2015 (UTC)
A few of the unreferenced items relate to EU requirements/standards, which tend to be rather expensively paywalled, so I will just remove the cn for things that are unlikely to be challenged, like the Hydro test period in Norway. • • • Peter (Southwood) (talk): 16:32, 6 June 2015 (UTC)

Peter's expansion of this section is very useful but I wonder about the following:

"The decrease in external volume of the cylinder due to reduction of internal pressure is relatively small, and can be ignored for practical purposes."
I'm pretty certain that the decrease in external volume is almost non-existent. If that were not so, my twinset would be dropping out of its steel bands every time the cylinders were empty - and that's with 300 bars of internal pressure to change their diameter. I agree that the lack of change of external dimensions is worth mentioning, but perhaps the simpler "The decrease in external volume of the cylinder owing to reduction of internal pressure is negligible." would be better? --RexxS (talk) 10:57, 6 June 2015 (UTC)

I am OK with that, but have actually noticed a change in tightness of tankbands between full and empty cylinders.  Still a trivial change of volume. • • • Peter (Southwood) (talk): 15:10, 6 June 2015 (UTC)
You've got to stop over-blowing your cylinders, Peter. :D I can't say I've ever noticed, but if you've seen a small effect, leave the wording as it is for accuracy. I suspect that for most rigs the cam-bands used have enough stretch to swamp any possible effect of cylinder shrinkage. Cheers --RexxS (talk) 15:35, 6 June 2015 (UTC)
Yes, I rely on my tank bands to prevent the cylinders from bursting, but they do tend to bulge a bit after a while.
More seriously, bear in mind that the modulus of the cylinder material is nearly the same as that of the bands, for steel cylinders, and at full pressure the stress in the cylinders is probably in the order of 200MPa. If there is no soft material between the cylinder and band, the strain in the band will be a significant fraction of that in the cylinder (if the clamping plates are reasonably rigid), so quite a bit of tension will be induced. However, I did a rough estimate and the volume change is negligible.
I have managed to find some references and fix a few discrepancies. Time to nominate? • • • Peter (Southwood) (talk): 19:42, 6 June 2015 (UTC)

Starting a list of illustrations which could improve the article. Just in case it encourages people to upload them to Commons.

Photos of diving cylinders at various stages of manufacture.
Exotic or unusual cylinders and configurations.
Please feel free to add to this list and strikethrough items as they become available on commons, even if not actually used in this article. • • • Peter (Southwood) (talk): 06:48, 25 September 2015 (UTC)

This review is transcluded from Talk:Diving cylinder/GA1. The edit link for this section can be used to add comments to the review.
Reviewer: Pyrotec (talk · contribs) 21:11, 24 December 2015 (UTC)


### Review intention
I am intending to review this article as the nomination has been sitting at WP:GAN since 11th June 2015 (and is the eight oldest nomination (see [1]) . However, looking at [2], I've done ten edits to this article, which represents 1.3% of the total number of edits to the article. I don't see this a "conflict of interest", but having posted this Note I'm going to wait one week so see if there are any objections on this basis, before I start reviewing. Pyrotec (talk) 21:11, 24 December 2015 (UTC)

Meanwhile, there are whole sections / subsections of this article that are unreferenced: Terminology (two out of three paragraphs); Parts of a cylinder (The pressure vessel; (most of) Aluminium cylinders; Manufacture; Steel cylinders; The cylinder valve, etc, etc, .....).; and Applications and configurations of diving cylinders, for starters.  I would have sufficient grounds to "quick fail" this article on that basis. That however, would be unfortunate, as the article appears comprehensive in respect of coverage and some parts of the article are well referenced. Furthermore, while this article might be "B-class" in terms of material content, it really aught to be "C-class" overall (see [3]) due to lack of citations, overall. I respectfully suggest that this time (see above) be spend productively. Pyrotec (talk) 22:05, 24 December 2015 (UTC)

Hi Pyrotec, Thanks for your comments so far. I am confident that I can easily reference almost anything that needs references. I am closely involved in the diving industry and most of the material seems obvious and common knowledge to me, therefore the value of your comments. As I have difficulty recognizing what may be controversial or may for other reasons need referencing, please just slap on a  for each paragraph/sentence you think needs a ref and I will get one. Most will probably be referenceable from the US Navy Diving Manual (available online) and the NOAA Diving Manual (not available online), which are somewhat large documents. If you want page numbers or section numbers please specify. This may take a little longer.
The article is looking much better now. Sorry, as this is a review I won't be putting  flags on the articles, they will itemised on this review page. My experience with cylinders etc is from a UK perspective, but some years ago I had access to ASTM, European and Nato diving documents (which is no longer the case). Pyrotec (talk) 13:29, 26 December 2015 (UTC)
As a rule-of-thumb, Peter, every paragraph in a Good Article should normally have at least one citation, if only to indicate the source of the information there. Another rule-of-thumb is that any article or journal entry that is no more than a few pages long doesn't need a page/section number, but any source longer than that ought to have an indication of where the citation refers, as a courtesy to the reader who wants to examine the source without having to read the whole of a lengthy document. Hope that helps, --RexxS (talk) 19:32, 25 December 2015 (UTC)

I have been adding references as I find them. Mostly it has been really easy, but I have not always been able to find good reliable sources available on-line, so a fair amount will require off-line checking, and a few of the references may be difficult to get in some parts of the world. So it goes. Alternatives may be available to other people that I can't get hold of too, so if you can fill in some of the gaps or supply alternatives, please do. I am also wondering how much I need to reference the calculations because they are basic physics, and my most useful reference is probably going to be difficult to get outside of South Africa. On the other hand, the same information should be available in several training organisations' manuals. • • • Peter (Southwood) (talk): 13:18, 26 December 2015 (UTC)
That's always a problem when you try to work on an article that others have written. Normally we should be reading the sources first and then writing the text; it's far harder work trying to justify someone else's unreferenced text. When I get a chance to fetch out the training manuals I have, I'll see if I can add any more cites. The principle behind verifiability is that somebody could reasonably access the source - it doesn't have to be everybody, so don't worry too much about citing documents that may be harder to find outside of SA, as long as somebody could find them in a library or archive, for example. --RexxS (talk) 15:16, 26 December 2015 (UTC)
The article is not going to fail on the gas calculations; and furthermore if its a "trivial problem" I may well fix it myself rather than log it here as a problem to be fixed by someone else. What I'm not going to do as a reviewer is to re-write sections (if that happens to become necessary for any reason). A reference for 10 metres of water = 1 bar would help (it's in the PADI manual but I don't think I have one to hand). Pyrotec (talk) 11:14, 27 December 2015 (UTC)
The reference for hydrostatic pressure in the USN Dive Manual is:
U.S. Navy Supervisor of Diving (2011). U.S. Navy Diving Manual (PDF). SS521-AG-PRO-010 0910-LP-106-0957, revision 6 with Change A entered. U.S. Naval Sea Systems Command. sec.2-9.3 p.134.
Although you have to know that 33 feet is approximately 10 metres and 1 bar is approximately 1 atmosphere (both of which are accurate to about 1%). Cheers --RexxS (talk) 13:15, 27 December 2015 (UTC)
Also in NORSOK U100, which was at <ref name="NORSOK U100">{{cite book|last=Staff|first=|title=NORSOK Standard U-100 :   Manned underwater operations |url=http://www.standard.no/PageFiles/13273/u100e3.pdf|edition=3|date=April 2009|publisher=Standards Norway |location= Lysaker , Norway}}</ref> but the link is dead now, possibly because the standard was revised in 2014. It seems to be paywalled now. • • • Peter (Southwood) (talk): 16:23, 6 January 2016 (UTC)
Also found a conversion site at http://www.translatorscafe.com/cafe/EN/units-converter/pressure/58-22/meter_sea_water-bar/ Would this be an acceptable reference? • • • Peter (Southwood) (talk): 16:46, 6 January 2016 (UTC)
And used my old BSAC manual. • • • Peter (Southwood) (talk): 17:08, 6 January 2016 (UTC)


### Initial review
I'm now going to work my way through the article, starting with Terminology going down to the end and then doing the Lead. This is likely to take a few days; and at this stage of the view I will mostly (perhaps entirely) be concentrating on any "problems" that I see. So, if a section / sub-section is not mentioned here, that implies that I've not found a problem (or perhaps there was a minor one that I fixed during the review).
Feel free to respond to a specific comment (in-line) beneath it. That way is a bit easier for me to keep track of the review.
After this is completed (or not), I'll give my assessment and hopefully award GA. Pyrotec (talk) 16:18, 4 January 2016 (UTC)
Terminology -
Looks OK. I added compressed to "..... typically contain (compressed atmospheric) breathing air, or ....", since "atmospheric" could be construed to mean "unpressurised". (N.B. otherwise, this section does not say that the gas is presurised; however as it is about the use of (a) cylinder(s) to provide breathing gas that implies the gas inside is compressed). Pyrotec (talk) 16:40, 4 January 2016 (UTC)
Thanks, your clarification may well help some readers. • • • Peter (Southwood) (talk): 05:43, 6 January 2016 (UTC)
Parts of a cylinder -
The pressure vessel -
I would not disagree with what is written in respect of composite cylinders, however I was told, perhaps 20 years ago, that another reason was that it would be (very) difficult to do a visual inspection for any external corrosion of the aluminium pressure vessel below it's fibre/resin wrap. Pyrotec (talk) 17:51, 4 January 2016 (UTC)
I have a vague memory of hearing the same thing, also that the filament wound cylinders are more expensive and have a limited service life, but I don't have any references for any of those statements. That they are lighter and more buoyant is testable by anyone with a scale and a bath of water. I know that for some military applications (multi-purpose rebreathers, like the Russian IDA 72) composite cylinders have been used, but those rebreathers are also used for high altitude parachute jumps, and though I actually own one, I have no citable reference. • • • Peter (Southwood) (talk): 05:43, 6 January 2016 (UTC)
This is more a problem with carbon fibre as glass fibre wrapping is to some extent translucent. Also, cylinders are commonly specified as suitable for a purpose by the manufacturing standard, and I don't know of any manufacturing standard for composite scuba cylinders, but I don't think that is in scope. • • • Peter (Southwood) (talk): 13:16, 21 January 2016 (UTC)
CFR Title 49: Transportation  PART 173—SHIPPERS—GENERAL REQUIREMENTS FOR SHIPMENTS AND PACKAGINGS  §173.301b   Additional general requirements for shipment of UN pressure receptacles. (g) Composite cylinders in underwater use. A composite cylinder certified to ISO-11119-2 or ISO-11119-3 may not be used for underwater applications unless the cylinder is manufactured in accordance with the requirements for underwater use and is marked “UW” as prescribed in §178.71(o)(17) of this subchapter. http://www.ecfr.gov/cgi-bin/text-idx?SID=9f2b8887057f9840be279234a83408d7&mc=true&node=pt49.2.173&rgn=div5#_top This may be relevant. storing it here in case it is useful. • • • Peter (Southwood) (talk): 14:43, 21 January 2016 (UTC)
It turns out that there are composite cylinders rated for underwater use, up to 300 bar WP, legal in USA and used by public safety divers. Relevant and referenced text has been added to the article in relevant sections. • • • Peter (Southwood) (talk): 10:07, 23 January 2016 (UTC)
Y. Thanks. Pyrotec (talk) 15:16, 27 January 2016 (UTC)
Aluminium cylinders -
What's "warm water", for diving? Perhaps a heated swimming pool rather than a quarry full of (cold) water, or may be Western Hemisphere Warm Pool? Perhaps its just the absence of the need for thermal insulated dive suits? Some clarification is needed.
It is a vaguely defined concept, Tropical waters where insulated dive suits are not required would be considered warm, waters where a dry-suit or 6mm wetsuit are needed would be considered cold, and there is a relatively vague intermediate temperature range, but I may be able to find a reference. • • • Peter (Southwood) (talk): 05:43, 6 January 2016 (UTC)
I have changed the wording so that it is clear that is not the water temperature that is relevant, but the suit buoyancy. • • • Peter (Southwood) (talk): 06:55, 6 January 2016 (UTC)
Y Thanks.  Pyrotec (talk) 14:07, 27 January 2016 (UTC)
Steel cylinders -
"cold water"? (see above).
As above, it is not the temperature that is relevant, it is the buoyant insulation worn because of the temperature. If you think this need further clarification, let me know (or do it yourself if you like) • • • Peter (Southwood) (talk): 07:26, 6 January 2016 (UTC)
Y Pyrotec (talk) 14:19, 27 January 2016 (UTC)
This subsection is unreferenced. Nothing controversial or counter-intuitive, but it does standout as unreferenced.
I will see what I can do. • • • Peter (Southwood) (talk): 05:43, 6 January 2016 (UTC)
Added a couple of references, let me know if you think they are acceptable. • • • Peter (Southwood) (talk): 07:26, 6 January 2016 (UTC)
Y Yes. Much better, thanks. Pyrotec (talk) 14:19, 27 January 2016 (UTC)
Connection to the regulator -
It would be helpful to have a citation for the DOT rule on (NOT) transporting 300 bar cylinders on public roads.
It is much quoted, but seldom cited. I will try to find it. • • • Peter (Southwood) (talk): 05:43, 6 January 2016 (UTC)
It is probably in 49 CFR 173.301 - General requirements for shipment of compressed gases and other hazardous materials in cylinders, UN pressure receptacles and spherical pressure vessels, but so far I have been unable to download a copy. I will try again. • • • Peter (Southwood) (talk): 07:50, 6 January 2016 (UTC)
I found a free site for 49 CFR 173.301, but could not find reference to maximum pressure allowed. I am continuing my enquiries, but if anyone can help please do. • • • Peter (Southwood) (talk): 14:54, 21 January 2016 (UTC)
I am getting non-citable input from public safety divers in the US that they have no problem transporting full 300 bar cylinders, mostly used for SCBA. Still looking for a citable source. • • • Peter (Southwood) (talk): 11:02, 22 January 2016 (UTC)
It seems that there is no specific pressure constraint, more that there are no DOT standards for 300 bar cylinder manufacture, and that most 300 bar cylinders do not have a special permit (exemption). The text has been altered to suit and is now in the Transportation section under USA. • • • Peter (Southwood) (talk): 08:21, 2 February 2016 (UTC)
Those two DIN regulators need a DIN or an EN number, or perhaps a supplier's web-page. If I were to go out a buy one it would mostly likely be to a BS EN standard, such as BS EN 144-3:2003 (http://shop.bsigroup.com/ProductDetail/?pid=000000000030110092) but I don't know if that one is one of the two mentioned. Pyrotec (talk) 19:35, 4 January 2016 (UTC)
Those documents are usually heavily paywalled, I can't afford to buy them just to check. I will look for a reference, but am reasonably sure that it is never specified in catalogs by suppliers other than by the thread count or pressure rating.• • • Peter (Southwood) (talk): 05:43, 6 January 2016 (UTC)
I found a few internet references. It looks like they all refer to the same source or to each other, as a lot of the text is identical in all of them, Maybe they will do. • • • Peter (Southwood) (talk): 15:55, 6 January 2016 (UTC)
I'm not expecting anyone to pay to get standards, but for instance in my public library I can log on using my library card to view, but not print nor save, British Standards. Those "A clamps" (from the figures along side) appear to be ISO 12209-2, so in the UK they might be available as BS ISO 12209-2 (or possibly BS EN ISO 12209-2) standards and perhaps in Germany as DIN ISO 12209-2 (or possibly DIN EN ISO 12209-2) standards; if so, I could view it. I was just hoping that some catalog such as e.g. http://www.midlanddiving.com/diving-equipment/din-basic-valves gives a standard No.; and perhaps you have an answer there.  Pyrotec (talk) 14:51, 27 January 2016 (UTC)
I have mentioned the standards in the text, but do not have access to them to reference in detail. • • • Peter (Southwood) (talk): 12:23, 30 January 2016 (UTC)
Does the valve shown on the MDE web page look like the "DIN" valve that you are talking about (I'm not familiar with DIN Valves)? If it does then the relevant specification is  EN ISO 10297:2006; and in the UK it would be a BS EN ISO 10296 valve (see http://shop.bsigroup.com/ProductDetail/?pid=000000000030317074 Note: the standard appears to have been updated in 2014. Pyrotec (talk) 19:34, 30 January 2016 (UTC)
The valve in the MDE link is an example of the lower pressure DIN connection which can be modified for yoke connector by addition of a threaded plug. As far as I know the EN and BS documents you refer to specify a large range of valve types for different applications and gases, probably including, but not restricted to, both the high and low pressure diving regulator and cylinder valve DIN connections. As I don't have access to the documents, I cant be more specific. • • • Peter (Southwood) (talk): 14:26, 31 January 2016 (UTC)
The original DIN standards are mentioned by number in the text. This should allow checking by anyone who has access • • • Peter (Southwood) (talk): 08:27, 2 February 2016 (UTC)
Pressure rating -
I'm  not too keen on those first three uncited statements.
EN 144-3:2003 is only mandatory in Europe, so "..... From August 2008, these were required for all diving equipment used with nitrox or pure oxygen" is somewhat controversial. I'm sure a European Directive could be found for Europe, but what about the rest of the world (the USA, etc).
As far as I know this only applies to Europe. I don't know, but cant imagine it having any status in the USA, and do know that it does not apply in South Africa. I have no information on other regions, but my best guess is that this is Europe only. I have changed the text to specify this. • • • Peter (Southwood) (talk): 08:16, 6 January 2016 (UTC)
YPyrotec (talk) 14:57, 27 January 2016 (UTC)
.... to be continued. Pyrotec (talk) 18:01, 4 January 2016 (UTC)

Reserve valves -
I've come across an abbreviation "SPG" which appears to be undefined before or anywhere else e.g. perhaps it is "submersible pressure gauge(SPG)"?
Correct. SPG is used by divers as a standard expression, almost as much as scuba, but a definition at first use would be appropriate. I have done this.• • • Peter (Southwood) (talk): 05:43, 6 January 2016 (UTC)
Y Pyrotec (talk) 14:57, 27 January 2016 (UTC)
Cylinder pressure rating -
OK.
Cylinder capacity -
OK (but references for the first three subsections would improve the article).
I will see what I can do.
Internal volume should not be a problem. -ref added.
Y Pyrotec (talk) 15:30, 27 January 2016 (UTC)
Standard sizes: I am not sure how to deal with this. Do you want each size cited (simple but very tedious), or each application cited (not so simple, even more tedious) or both, or something else?
The easiest approach is go give a web link to the relevant info. at Faber, Pressed Steel, Luxfer, and/or Catalina. Pyrotec (talk) 15:30, 27 January 2016 (UTC)
That will work for citing sizes. It mat take a while to get them all. • • • Peter (Southwood) (talk): 10:32, 30 January 2016 (UTC)
Done for steel cylinders and some US aluminum cylinders• • • Peter (Southwood) (talk): 14:26, 31 January 2016 (UTC)
Y Pyrotec (talk) 19:44, 5 February 2016 (UTC)
Nominal volume of gas stored has two citations already. I can probably get more if you are specific about what needs the citation. • • • Peter (Southwood) (talk): 09:02, 6 January 2016 (UTC)
Y I'm happy with what is there now. Pyrotec (talk) 15:30, 27 January 2016 (UTC)
Applications and configurations of diving cylinders -
.... to be continued. Pyrotec (talk) 20:10, 4 January 2016 (UTC)

Most of this section is unreferenced or sparsely referenced. Arguable the text down to Rebreathers possibly has adequate references; as does the final paragraph: For safety, divers sometimes carry .....
The two paragraphs that appear to be concerned with Rebreathers are unreferenced.
Has been referenced, please check if sufficient. • • • Peter (Southwood) (talk): 13:10, 21 January 2016 (UTC)
There appears to have been a minor reorganisation, so any relevant comments now appear below. Pyrotec (talk) 18:06, 29 January 2016 (UTC)
Open-circuit scuba -
This subsection is almost without references (it has one only); and non-compliant with WP:WIAGA clause 2.
In particular it is making "Recommendations" and/or "not-recommended", stating National practice(ices); personal opinions, i.e. "Some divers consider that ....".
That comment was intended as a report that the opinion is held by some divers, not as a recommendation or guidance. However I have changed the wording. As I understand it it is acceptable to report national practices, organisational recommendations and general trends provided that they are not represented as anything else. At present I have no reference to cite, so have removed the report of a common opinion.
Also looking for more refs • • • Peter (Southwood) (talk): 10:28, 6 January 2016 (UTC)
Y Pyrotec (talk) 13:58, 31 January 2016 (UTC)
Closed-circuit Rebreathers -
This subsection is entirely without references.
Will look for refs. • • • Peter (Southwood) (talk): 10:28, 6 January 2016 (UTC)
Good one added by user:Gene Hobbs • • • Peter (Southwood) (talk): 06:25, 7 January 2016 (UTC)
Y Thanks. Pyrotec (talk) 17:37, 29 January 2016 (UTC)
Surface supplied diver emergency gas supply -
OK.
Emergency gas supply on diving bells -
The statement "Diving bells are required to carry an on-board supply of ...", aught to have a citation.
Added refs from two IMCA documents accessible online. • • • Peter (Southwood) (talk): 10:23, 30 January 2016 (UTC)
Y Pyrotec (talk) 19:53, 30 January 2016 (UTC)
Gas calculations -
The abbreviation "IMCA" needs introducing, or wikilinking, at its first occurrence.
Done • • • Peter (Southwood) (talk): 10:23, 30 January 2016 (UTC)
Y Pyrotec (talk) 19:53, 30 January 2016 (UTC)
BCD appears here and in Safety, but I think here is its the first occurence (I know what it is), but it needs introducing, or wikilinking.
Done • • • Peter (Southwood) (talk): 10:23, 30 January 2016 (UTC)
Y Pyrotec (talk) 19:53, 30 January 2016 (UTC)
In Diver gas consumption: "msw" and "fsw" need introducing, or wikilinking, at their first occurrence (as per "cfm"). Note: I worked out the first one immediately, but the second stumped me for few minutes.
Wikilinked to glossary. • • • Peter (Southwood) (talk): 10:23, 30 January 2016 (UTC)
Y Pyrotec (talk) 14:08, 31 January 2016 (UTC)
In Breathing gas endurance: should "cracking pressure" be introduced, or wikilinked, as it appears to be a technical term?
Linked to glossary definition • • • Peter (Southwood) (talk): 10:57, 30 January 2016 (UTC)
Y Pyrotec (talk) 14:08, 31 January 2016 (UTC)
Gas calculations are mostly elementary physics, so may not need citation, but could be referenced if it is necessary or desirable, as they are standard to many training manuals. • • • Peter (Southwood) (talk): 06:25, 7 January 2016 (UTC)
Y The BSAC ref (Ref 52) adequately covers this, so I'm not asking for any addition citations. Pyrotec (talk) 19:06, 29 January 2016 (UTC)
Filling cylinders -
Considering the first paragraph, only for now: what is written in sensible and good advice, but I have two comments:
When filling an oxygen cylinder the requirement is breathing quality oxygen, so perhaps we don't necessary need a gas blender? Note: in the paragraph below, oxygen decanting is covered, so perhaps a minor edit in needed.
Added decanting as an alternative technique as it is applicable for mixes and air as well as oxygen. • • • Peter (Southwood) (talk): 10:39, 30 January 2016 (UTC)
Y Thanks.  Pyrotec (talk) 13:20, 1 February 2016 (UTC)
I'd suggest that there are addition constraints: The filling is done by the cylinder owner, or his representative (in the UK I can't rent an industrial gas cylinder and refill it myself; perhaps, if I've rented a dive cylinder I can pay any dive shop refill it, but perhaps I have to take it back to the owning diveshop?). The cylinder should be capable of accepting the gas charge (i.e. don't put 300 bar into a 200 bar cylinder) and the cylinder is within it's period test and inspection date(s). Note: The need for the cylinder to be correctly labeled as to its intended contents: however, that appears in the paragraph below and in the Safety section. I suggest a link or a "(see Safety section) is added.
I will mention legal constraints which will vary by jurisdiction. I don't know what they are in most places. In SA you need written permission from the owner of the cylinder to fill it, the cylinder must be in test and suitable for the gas to be filled, the cylinder may not be filled above the developed pressure for the temperature reached when it is filled, and it must be done by a competent person. This is probably a fairly common arrangement, but I have no references for other countries. • • • Peter (Southwood) (talk): 11:21, 30 January 2016 (UTC)
If you or RexxS or Gene Hobbs can help with either the some referenced text or suitable online references for the situation in UK and USA, it would be appreciated. Similar for other countries if possible. • • •Peter (Southwood) (talk): 12:20, 30 January 2016 (UTC)
Y Thanks.  UK guidance can be found in B.C.G.A. G.N. 17 (free to download). Pyrotec (talk) 13:20, 1 February 2016 (UTC)
Last but one paragraph: "Contamination by water during filling ...". If it's an oil lubricated compressor, it will not be "fresh Water", more likely, water and oil/water emulsion.
I have added emulsion as a possible contaminant, but it is possible to get water contamination if the oil is adequately removed but the air is still too humid with water vapour which can condense in the cylinder on cooling. I have seen many compressed air purity tests which fail only on water content. - oil, CO and CO2 well inside limits, but high moisture content, and the moisture is usually not liquid in the air supply from the compressor. This may be a consequence of a warmer climate.• • • Peter (Southwood) (talk): 11:30, 30 January 2016 (UTC)
Y Thanks. Pyrotec (talk) 13:20, 1 February 2016 (UTC)
Inspection and testing -
OK.
Safety -
First paragraph is OK.
As is the second paragraph in correct (in theory), but see also the last paragraph of Filling cylinders. What about a sniff test, or a function test on the valve, on a full 300 bar cylinder, etc.
I have clarified, check if satisfactory.• • • Peter (Southwood) (talk): 12:42, 30 January 2016 (UTC)
Y Thanks. Pyrotec (talk) 20:17, 5 February 2016 (UTC)
Accidents, Handling -
OK
Long term storage -
In general what is written in correct, however I don't think that is the full story: there is (generally) a five year cylinder inspection cycle, so cylinders outside their inspection period "aught" not to be used. If they were medical gases (which they are not), the contents would be "life-ed" and good storage guidelines would insure that oldest stock was issued first (the cylinders may not have a filling date, but there might be a filling certificate which would be dated and signed) and that might be cylinders with the least "life" left on their cylinder test cycle.
Scuba cylinders have different inspection/test cycles in different countries, and I know that In SA there is no restriction on using an out of test cylinder, but it may not be filled, so no local restrictions on transporting out of test in SA, but for commercial purposes transport of cylinders in US the DOT requirement is they must be in test if filled to over 40psi (IIRC). I don't have information on other countries. It gets complicated. If you have any suggestions, please go ahead. • • • Peter (Southwood) (talk): 11:30, 30 January 2016 (UTC)
Y Pyrotec (talk) 20:00, 5 February 2016 (UTC)
.... to be continued. Pyrotec (talk) 19:06, 29 January 2016 (UTC)

Transportation -
This is entirely USA-based and broken down into USA, (USA) land and air. Europe for instance, would not accept DOT cylinders unless they were also to EN or ISO standards.
From a global perspective (which is what wikipedia needs): there is land transportation (with separate Road and Rail agreements), sea transportation and air transportation. Land (Road) transportation of Dangerous Goods (filled cylinders) is covered by U.N. Regulations (and in Europe we have ADR rules as well); sea by International Maritime regulations; and, air by International Air Transport Association regulations (see Dangerous goods, UN Recommendations on the Transport of Dangerous Goods, International Maritime Dangerous Goods Code and International Air Transport Association).
Perhaps a {{see also}} or a {{main}} link to Dangerous goods might be helpful for the reader. Since this is a "personal suggestion", as I GAN Reviewer I can't enforce this one.
Any suggestions that will improve the article for the user will be incorporated if reasonably practicable. I am constrained by the available references. I have access to most of the relevant legislation for SA, as I work with it, and for the USA as they have the admirable tendency to make federal legislation freely available on the internet. Other countries often paywall this sort of information. • • • Peter (Southwood) (talk): 12:42, 30 January 2016 (UTC)
Note: the UN agreement and the European ADR and RID agreements are (were) on the web but are large multiple pdf files - they are updated almost annual. IATA has to be bought annually in either book or CD form.
I have never worked with this stuff. If you know the links or the appropriate search strings, they would be appreciated. • • • Peter (Southwood) (talk): 12:42, 30 January 2016 (UTC)
See in the first instance: http://www.bcga.co.uk/pages/index.cfm?page_id=31&title=transport_matters For the UN and ADR agreements see:  http://www.unece.org/trans/danger/danger.html or http://www.unece.org/?id=3598 On the left hand side "ADR" is the European agreement on carriage of Dangerous roads by Road. http://www.unece.org/trans/danger/publi/unrec/rev19/19files_e.html is the link to the UN Model Regulations.  If you are not familiar with this area, I suggest that http://www.unece.org/fileadmin/DAM/trans/danger/publi/unrec/GuidingPrinciples/Guiding_Principles_Rev19 is looked at. Gases are Class 2. The UN Model Regulations is nearly 1,000 pages in total, I used to have a hard copy on my shelf at work: working with two pdf files of about 450 page each is not "fun" (don't do it).  Pyrotec (talk) 20:15, 30 January 2016 (UTC)
ADR (Europe and by Road) is 1254 pages long, but gases are Class 2 (also subdivided on sub-class). ADR does not apply to gases in retail packaging for THEIR personal, domestic, sporting activies, etc (so the diver can carry their own cylinder(s) Para 1.1.3.1 (page 6 of the annex - 30 of the pdf file), but that excludes diveshops etc; nor to uncleaned cylinders containing less than 2 bar (para 1.1.3.2 (c) - pdf 31). Para. 1.1.3.3 refers to excepted quantites, specifically para 1.1.3.3.6 (pdf - 34) so there is a 1000 kg net mass (i.e. gas mass) for typical diving gas mixtures, above that ADR applies.{At one time I vaguely remember that equated to W.C. so 1000 kg = 100  filled 10 litre cylinders, or 95 10.5 litre ones}. Note: under ADR its a 10 year (max) inspection and test cycle. Pyrotec (talk) 08:28, 31 January 2016 (UTC)
I found the file: it is, as you say, large, and not easy to search. However it appears to correspond very closely to the information I got from the UK Guidance note 27. The excepted quantity/threshold for Class 2,2 is indeed 1000litres WC, not 1000kg. 10 year cycle is typical for industrial cylinders, diving cylinders in Europe is 5 years hydro test and 2.5 years visual inspection. This is already in the article. I will check that there are no differences between GN27 and ADR, and add the ADR references. • • • Peter (Southwood) (talk): 18:03, 31 January 2016 (UTC)
Actually, it's the other way round. GN 27 is UK (national) guidance on how comply with ADR; and ADR is an European agreement at the UNECE on Road transport of DGs, based on the UN Model Regs for transport of DGs. I agree that in diving its a 2.5 & 5 year inspection / test cycle (as per the comments above). However the UN Model regulations have very detailed (design requirements) requirements on what they call "packaging", but it's specifically the design specification for the cylinder, valve, labelling, colour coding, testing etc. The fact that dive cylinders have shorter test cylinders is neither here or there (since it is "better" than the UN Model Regs) on whether it is "legal" to transport these dangerous goods.  See Packing Instruction 200 (pages 39 - 53 and Chapter 6.2 in Volume II, (Note: P.I. 200 = pdf pages 49 - 63 and Chapter 6.1 = pdf 221 ff) at http://www.unece.org/trans/danger/publi/unrec/rev19/19files_e.html  Note: as I think the article already states, in diving it's (at most) UN 1002, 1006, 1046, 1066 & 1072 gases. [I find it easier to use printed copies of the whole Regs., but I'm not printing this lot out at home). Pyrotec (talk) 12:29, 1 February 2016 (UTC)
Yes, Like you said. So if GN 27 and ADR say the same thing, it should be good for Europe in general, and UK in specific. I will look at PI200, and those additional UN gases you mention. I do not understand the relevance of the 10 year test cycle for diving cylinders. As I understand it, they must be in test to be filled. Can they be transported out of test for diving purposes but within 10 years of last hydro/inspection? I have not seen anything anywhere to state this is then case, nor that it isn't. I know the requirements in SA, but have never needed to know them for other countries. • • • Peter (Southwood) (talk): 11:01, 2 February 2016 (UTC)
Consider, first, industrial gas cylinders: they have a ten year inspection cycle and the UN Model Regulations also require a ten year test cycle. They can't be filled if the test(s) are out of date: they have to be (re-)tested first. It's not entirely clear to me, but it's possible that they can't be transported (as DGs) if they are out of test date (The methodology is: exceptions on "limited quantities", blanket prohibition, allow if compliance with annexes, and Special Provisions). However, vent them to below the pressure limit and they can be transported outside of the D.G. Regs. Now Diving cylinders can't be refilled if they are out of date on the test cycles (inspection and test, which are different), but it appears that if the tests are less than ten years old they can be transported filled under the DG Regs. Pyrotec (talk) 20:13, 5 February 2016 (UTC)
Only the depth varies... Thanks, I will see what I can make of this. • • • Peter (Southwood) (talk): 08:38, 31 January 2016 (UTC)
USA -
OK as far as it goes.
Surface transport -
OK as far as it goes.
Air transport -
In my opinion this is only applicable to USA domestic flights, but (and the picture is much much more complicated) it sort of applies to international flights. However, I suspect (I don't have knowledge of USA regs) that it is not a "carry on" i.e. locker item it would be hold luggage only; and, at the discretion of individual airlines (even pilot). Therapeutic oxygen to keep a passenger alive is very different - it going to be carry on (where the bottle is compliant).
The same procedure holds good for SA internal flights last time I carried a cylinder. Most scuba cylinders are too big for carry-on - mine certainly were. Therapeutic carry-on is outside the scope of Diving cylinder. • • • Peter (Southwood) (talk): 12:51, 30 January 2016 (UTC)
I'm somewhat surprised, but the UK's CAA allows scuba cylinders containing below 200 kPa (2 bar or 29 psi) (see https://www.caa.co.uk/Passengers/Before-you-fly/Baggage/Items-that-are-allowed-in-baggage/ look under sports). So that is consistent with the USA. The airlink could still refuse, but in that condition they are not prohibited under CAA rules. Pyrotec (talk) 19:45, 30 January 2016 (UTC)
It's not too surprising because in the UK most ABLJs and many early stab jackets had a small cylinder used to inflate the device, before direct inflators from the first stage became common. These small cylinders, which were filled by connecting them to a normal dive cylinder, provided a very limited amount of redundant gas supply. When flying, nobody in their right mind would carry a full-sized cylinder, but it was quite normal to carry the small cylinders (empty with the valve open) along with your own BCD as hold luggage. The attitude of the airlines and the regulations would have been drawn up with that sort of use in mind, and I don't suppose anybody ever saw any need to change them. --RexxS (talk) 00:51, 31 January 2016 (UTC)
(missing) International overview -
Separate, Road (& Rail ?), Sea and air subsections.
(missing) Surface transport -
could be done as per USA subsection (above) but by reference to UN Model agreement (possibly) referencing ADR in Europe (since the documents are (were) free to view.
I will see what I can find out. • • • Peter (Southwood) (talk): 12:51, 30 January 2016 (UTC)
.... to be continued. Pyrotec (talk) 08:39, 30 January 2016 (UTC)

Gas cylinder colour-coding and labeling -
Worldwide -
It would be useful to have an in-line ref. for  "..... nitrox cylinders are colour-coded with a green stripe on yellow background". (Note: You have a nice picture, which I'll accept if you can't find a ref).
Not my contribution. SA rules require different colours as specified with ref below. I don't know where this comes from. Green band does seem to be relatively common (OR) but I have no ref. Will change to indicate that is is used but not necessarily required. • • • Peter (Southwood) (talk): 13:36, 1 February 2016 (UTC)
The green/yellow band seems to be ubiquitous in the USA, but in the UK, I have to mark my nitrox cylinders with the lower band shown in File:Cylinder mod.jpg if I want them to be filled. I think the amendments that you've made better reflect the different practices. --RexxS (talk) 17:35, 1 February 2016 (UTC)
Sorry, in my experience, I'd tend to (middly) disagree with: "The normal colour of aluminium diving cylinders is their natural silver". Aluminum is fairly reactive and tends to tarnish to form a "surface oxide" and that is intentionally done in a passivating process: anodising. All the Lufer aluminum cylinders I've bought as "trade sales" from M.D.E. or Sea and Sea, between 1991 and about 2000, have been painted: the early ones light or dark blue, or silver-coloured, and the newer ones yellow (as mentioned),I've seen white as well); I did not specify surface finish, only material (Al.), W.C., pressure and type of outlet valve. In addition, I've rented industrial gases (special analytical grade) and they have come in (apparently) plane "semi-polished" aluminum cylinders, but I think that they were treated (may be lacquered or anodised) rather than "bare" - a bit like the alloy wheels on my car: a "silver paint and lacquer" finish - only bare where / when I scraped the curb. Pyrotec (talk) 13:09, 1 February 2016 (UTC)
Also not my claim. I have seen self-colored aluminium cylinders advertised on many websites, but in practice most that I have seen and used have been painted. In SA it is required, they must be yellow. On the other hand, when anodised, unless the anodising is dyed, the colour could reaonably be described as the natural silver. • • • Peter (Southwood) (talk): 13:36, 1 February 2016 (UTC)
I can confirm that in the UK, Luxfer aluminium cylinders were painted metallic blue for many years prior to 1991 as well. I must admit that just about every Al-80 that I've dived with in the USA has been unpainted though. Again, Peter, your latest amendments are accurate, but I have no idea where to get references for them from. What is common knowledge among divers (the "sky is blue" analogy) is often difficult to support with a reliable published source. I'm guessing it would take some 'original research' to trawl through older paper dive magazines (Skin Diver, Sport Diver, etc.) which may have adverts and reviews that could be used. --RexxS (talk) 17:35, 1 February 2016 (UTC)
European Union & South Africa -
OK.
WP:Lead -
.... to be continued. Pyrotec (talk) 13:11, 1 February 2016 (UTC)

This should both introduce the topic article (but not include material which is not in the body of the article) and give a summary the body of the article that is balanced in the same proportion as the body of the article. It should, in general, be no more than three or four paragraphs.
The first paragraph looks OK.
The second paragraph is very "light" and not really representative. For instance testing and and inspection is mandatory if the cylinder is transported commercial as DGs.
Most of what is in the final paragraph does not appear in the body of the article, and so this is a "wasted paragraph" in respect of the limited number available. First aid treatment of Diving disorders does not appear in the body of the article, but decompression stops, different gas compositions (in technical diving), bailout bottles etc, and reserves / endurance are.
Emergency supplies in respect of Surface-supplied and diving bells, form an almost insignificant fraction of the body of the article (by number of words), but its almost half of this paragraph. Pyrotec (talk) 21:06, 5 February 2016 (UTC)

I've copyedited the lead to try to cover the sub-topics that are IMHO most pertinent to the casual or lay reader. I've attempted to explain more terms and include a couple of important topics that I would normally teach to newcomers, but I've completely cut the fourth paragraph because I don't believe the article benefits from dwelling on non-diving uses in the lead. @Peter: Please feel free to re-edit, revert or whatever you feel best. Cheers --RexxS (talk) 22:21, 5 February 2016 (UTC)
Y. Excellent summary. Pyrotec (talk) 08:26, 6 February 2016 (UTC)
Other.
Thanks for diligently addressing my comments. Unfortunately I'm running out of time. Admittedly time was lost at the beginning, due to me, but reviews should normally take about one week. I'd like to close this review within 30 hours from now, since I'm not going to be editing after then. Pyrotec (talk) 21:18, 5 February 2016 (UTC)


### Overall summary
GA review – see WP:WIAGA for criteria

Is it reasonably well written?
A. Prose is "clear and concise", without spelling and grammar errors: 

B. MoS compliance for lead, layout, words to watch, fiction, and lists: 

Is it factually accurate and verifiable?
A. Has an appropriate reference section: 

B. Cites reliable sources, where necessary: 

C. No original research: 

D. No copyright violations nor plagiarism: 

Is it broad in its coverage?
A. Major aspects: 

B. Focused (see summary style): 

Is it neutral?
Fair representation without bias: 

Is it stable?
No edit wars, etc: 

Does it contain images to illustrate the topic?
A. Images are tagged with their copyright status, and valid fair use rationales are provided for non-free content: 
Yes, and many provided by the nominator of this article at WP:GAN
B. Images are provided if possible and are relevant to the topic, and have suitable captions: 
Yes, and many provided by the nominator of this article at WP:GAN
Overall:
Pass or Fail: 

This article has been considerably improved during the course of this review. Especially in respect of unreferenced sub-sections and paragraphs (and there were a lot), but also in expanding / internationalising subsections which were solely US-directed. Thanks very much for the efforts and time expended in making these considerable improvements. I'm therefore awarding GA-status.
As a neutral observer (if that is possible), I consider that this article has sufficient breadth and scope to make it through WP:FAC if that path were to be taken (this is not a recommendation either way). HOWEVER, the main problem (as per the start of this review) is inadequate in-line citations (for FA) and possibly grammar, etc, so it would possibly a mistake to rush into WP:FAC; it would be far better to read some reviews to see the process in action and fix those missing citations,
Finally, it has been a pleasure to review this  nomination, some are "hard", but not this one.
Congratulations. Pyrotec (talk) 08:26, 6 February 2016 (UTC)

Thanks, Pyrotec It has been a pleasure working with you. Perhaps we will meet again, some day, on a similar project. This exercise has been interesting and entertaining, and occasionally fairly challenging. Overall a worthwhile experience, and the article is more improved that I had thought likely. A fresh perspective is clearly a thing of great value. Thanks also to RexxS and Gene Hobbs for support. I have a few more articles nominated for GA which I would like to get through before moving on to FA. There is no great rush. • • • Peter (Southwood) (talk): 13:22, 6 February 2016 (UTC)

Seems that maybe the Brits are tired of harmonizing with "European norms" in dive equipment. Perhaps they feel, like Americans, that Europeans and their norms can go and suck some carbon monoxide. Heh. Whatever floats your boat or sinks your BC, Europe. You go, girls. SBHarris 23:03, 24 June 2016 (UTC)

Sorry, I don't get your point. Please clarify. • • • Peter (Southwood) (talk): 14:09, 26 June 2016 (UTC)

Peter - Warning: Anecdote.
"it is not possible for water to get in during the dive". Actually, it is. Some years ago, a buddy of mine was diving a wreck lying on a slope, using twin independents. The shot line used for descent had dropped onto the deepest part of the wreck. He was so interested in the wreck he failed to monitor his gauges and ran one cylinder out of air when he had worked his way to the highest point. He then switched to his other cylinder - without turning off the 'empty' one - and finished the dive by working his way back down the wreck to the shot line and made his ascent. Back on the boat, none of us were surprised when we could hear water sloshing around in the cylinder that had run out of air.
Of course there was air left in the cylinder when he ran out of air - at least the water pressure at that depth - but taking that cylinder back down to greater depth can provide sufficient reverse pressure. The upstream valve that he was diving with ("I prefer it because it doesn't freeflow"), was the final piece of the jigsaw needed to ensure that we spent that evening emptying and drying out the cylinder before it could be refilled. It seems that nothing's impossible. --RexxS (talk) 14:03, 14 July 2016 (UTC)

RexxS
Yes, agreed. unless the cylinder had been submerged deeper than where the last gas was used it is not possible for water to get in during the dive is how I put it, which is exactly what happened to your friend. Nothing is foolproof. He was actually lucky that enough got in to be noticeable, otherwise he would probably have lost the cylinder at the next inspection. Water does get in from time to time, but probably more often when third world compressor operators fill cylinders that have been transported under dripping wet gear and don't check the inlet opening is clean before connecting up. That way only a small amount gets in, so not easily noticed, but enough to accelerate corrosion severely
Do you think I should make that statement more clear?. • • • Peter (Southwood) (talk): 15:56, 14 July 2016 (UTC)

Nah, Peter, you need a peculiar set of circumstances, and almost all second stages are downstream these days, so chances are very slim that anybody reading the article will be mislead. My experience with third-world filling stations is that the likeliest source of water is the compressor itself when they neglect to maintain it regularly. You obviously have the luxury of working with better trained operators than I do :P Cheers --RexxS (talk) 16:37, 14 July 2016 (UTC)

Maybe you just have slightly different third world experience. My anecdote is from Mozambique, where the resort management are usually reasonably conscientious and are often foreigners with some experience of how things should be done, usually PADI instructors or the like, but they hire locals to do the grunt work and don't train them properly, or the locals don't actually care, or both. So the filters get changed by the boss, who stands to lose custom if the air is dodgy, but the cylinders get filled by the uneducated local who is in a hurry and doesn't understand the problem, and doesn't pay for the damage, and is in any case at a higher risk of being blown up by an old landmine in the bush than by a corroded cylinder, so may take a somewhat cavalier attitude to the whole personal risk issue.
Any of the servo-assisted Poseidon second stages could leak back through the second stage under a reverse pressure differential, as they rely on interstage pressure to keep the second stage valve closed. While we are on anecdotes, on the same trip that my friend had his new 15l steel contaminated with seawater to the extent that it failed visual later that year, I did my last dive with a Posiedon Jetstream, which free-flowed on me at 30m when I sent up my DSMB and basically emptied my cylinder in seconds. I got octo from my buddy and we surfaced without problems, safety stop and all, but I removed the Jetstream that day and replaced it with an Apeks, and have never gone back. • • • Peter (Southwood) (talk): 07:02, 15 July 2016 (UTC)

Since tank valves need to be periodically removed for internal visual inspection, do the US/Imperial taper threads on the tank or valve eventually wear out from repeated removal and reattachment?
The main intent of the US/Imperial National Pipe Thread (NPT) taper is apparently to mechanically squish and deform the metal pipe threads, to make a permanent metal-to-metal gas-tight seal between two potentially imperfect hand-threadings. Repeated disassembly does not seem to be intended, or even desirable with torqued taper threads.
Though I suppose if the metal alloy of the valve side is softer than the tank alloy, the tank threads would be less likely to deform from repeated disassembly, but the valve may need to be discarded or reshaped with a threading die periodically. -- DMahalko (talk) 18:21, 2 August 2016 (UTC)

I'm pretty certain that the valve thread is noticeably harder than the cylinder thread. But as I understand it, taper threads on dive cylinders are always sealed with thread seal tape, so the PTFE ensures the seal against imperfect machining, rather than deforming a metal-to-metal contact. You just renew the tape after visual inspection and as long as you don't exceed the recommended torque, the cylinders don't suffer from thread failure, in my experience. That's anecdotal, of course, but I don't know of a reliable source that addresses the issue. --RexxS (talk) 19:43, 2 August 2016 (UTC)

The threads do wear out. In the case of a steel cylinder the threads on the valve usually wear out faster as the valve is almost always brass. This is cheaper to fix as a new valve is usually cheaper than a new cylinder. Aluminium tank threads are softer than the valve and will wear out first, or may bind and gall, which damages both threads at the same time. Taper threads on aluminium cylinders are less common in my experience, but this may be a regional thing. In general, taper threads are now less often found on scuba cylinders than in the past, probably for this reason, but in some cases for legal reasons too. In South Africa it is no longer legal to market new cylinders with taper threads for scuba, though the large steel storage cylinders still use them. As RexxS mentions, taper threads on HP cylinders are fitted using either thread tape (usually PTFE) or soft lead covers (not seen on scuba cylinders by me), both of which are much softer than the metal of the threads, and which deform to fill the gaps and make a seal while lubricating and preventing the threads from coming into direct metal to metal contact over most of the surface. This both provides a better seal and reduces the thread deformation to an acceptable level so that the valve can be removed and replaced several times before wear is excessive. Re-threading is usually not possible as the refurbished thread will be smaller than the permitted tolerances and will fail the gauge tests. There are international and national standards for thread form, and manufacturers specifications for torque.  Also training manuals and procedures for visual inspection of cylinders. These would be reliable sources. How much of this do you think is in scope for this article? • • • Peter (Southwood) (talk): 05:26, 3 August 2016 (UTC)
The lead caps are not for use on aluminium cylinders. • • • Peter (Southwood) (talk): 12:11, 5 August 2016 (UTC)

Meta:Wikipedia_is_not_paper and so there is no problem with the article being as long and detailed as is necessary to fully cover any relevant topic area. -- DMahalko (talk) 12:36, 3 August 2016 (UTC)

My point is whether it is still relevant to this topic to go into thread standards. I guess I will put stuff in and if it gets too much, split it off. Been there, done that. • • • Peter (Southwood) (talk): 15:46, 3 August 2016 (UTC)

Thanks, Peter. The only taper thread cylinder I've used was an old aluminium one, but as you say, it may be a regional thing. I appreciate that we could get sourcing on the background to cylinder/thread construction and maintenance, but to address the original question, I've been looking for sources concerned with the failure of taper threads, particularly for examples of the mechanism and for some idea of how common such failures are. I've not yet had any luck. Perhaps you or Gene might have come across some? --RexxS (talk) 15:21, 3 August 2016 (UTC)
I will dig around in my paper files. There should be something somewhere. • • • Peter (Southwood) (talk): 15:45, 3 August 2016 (UTC)
I found a mention in SANS 1825:2005 Table 3. Basic equipment for test stations: Gauging is mandatory to ensure the integrity of parallel threads. In the case of taper threads where the gauge exceeds the maximum gauge limit remachining may be considered at the discretion of the competent person. The same document references SANS 6406/ISO 6406 Periodic inspection and testing of seamless steel gas cylinders and SANS 10461/ISO 10461 Seamless aluminium alloy gas cylinders - Periodic inspection and testing. Unfortunately I don't have either, but I will make inquiries. • • • Peter (Southwood) (talk): 18:12, 3 August 2016 (UTC)
Somewhat to my surprise I found pdfs of both on the net. https://law.resource.org/pub/us/cfr/ibr/004/iso.6406.2005.pdf, and https://ia800306.us.archive.org/21/items/gov.law.iso.10461.2005/iso.10461.2005.pdf I will get back after I have had a read. • • • Peter (Southwood) (talk): 18:26, 3 August 2016 (UTC)
With these references it should be possible to create an article on Testing and inspection of diving cylinders. • • • Peter (Southwood) (talk): 18:44, 3 August 2016 (UTC)
I have added a fairly comprehensive section on inspection and testing as specifically relates to diving cylinders - left out the stuff for other applications. Open for comment and suggestions. RexxS, I cant work out how best to use {{sfn}} for ISO documents, as they don't really have a useful author name (written by a committee), Do you know a workaround or better option? • • • Peter (Southwood) (talk): 10:22, 5 August 2016 (UTC)

Nice work, Peter. You can use {{sfn}} with any identifier you want as long as you explicitly refer to that identifier using a matching {{sfnRef}} in the full definition of the reference (instead of |ref=harv . For example in Oxygen toxicity, I used {{sfn}} to cite the U.S. Navy Diving Manual in the text like this:

{{sfn|U.S. Navy Diving Manual|2011|p=44|loc=vol. 1, ch. 3}}

{{sfn|U.S. Navy Diving Manual|2011|p=22|loc=vol. 4, ch. 18}}

etc.

and then in the Sources section, made the full definition like this:

* {{cite book
  | author = U.S. Navy Supervisor of Diving
  | title = U.S. Navy Diving Manual
  | version = SS521-AG-PRO-010 0910-LP-106-0957, revision 6 with Change A entered
  | year = 2011
  | publisher = U.S. Naval Sea Systems Command
  | url = http://supsalv.org/pdf/Dive%20Manual%20Rev%206%20with%20Chg%20A.pdf
  | format = PDF
  | accessdate = 29 Jan 2015
  | ref = {{sfnRef|U.S. Navy Diving Manual|2011}}
  }}

The short references show up in the References section where the {{reflist}} template is placed and link to the full definition in the Sources section. The {{sfnRef}} template takes a number of "authors" (or whatever you want) and a year to match the ones you used in the {{sfn}}. Does that make sense? --RexxS (talk) 16:02, 5 August 2016 (UTC)

Thanks, that looks perfect. I will see if I can get it to work when I get back from diving. Cheers, • • • Peter (Southwood) (talk): 04:52, 6 August 2016 (UTC)
Done. Works as advertised. Thanks, • • • Peter (Southwood) (talk): 18:07, 6 August 2016 (UTC)

Please use (or at least include) SI units.  E.g. ..maximum working pressure rating from 184 to 300 bars (2,670 to 4,350 psi).

1 bar = 100 kPa=0.1 MPa, so conversion should not require a calculator.
In this case kPa would probably be the most familiar.
So the pressure would be 18400 kPa to 30000 kPa or 18.4 to 30 MPa (would probably be easier to read under water. )   — Preceding unsigned comment added by 75.73.1.89 (talk) 22:27, 4 November 2016 (UTC)

What advantage would this have? I know of no diving equipment making use of any pressure units other than psi (USA) or bar (elsewhere). I've never seen a submersible pressure gauge marked in MegaPascals: have you? Sources use psi or bar (sometimes atmospheres absolute, ATA, or feet/metres of sea water, fsw, msw) as do all the training materials that I'm familiar with. Not one uses Pascals that I'm aware of. For what it's worth, SI_derived_unit #Other units used with SI specifically mentions the bar, which is by definition 100 kPa - as you say, it's easy for anyone used to SI units to understand. --RexxS (talk) 23:30, 4 November 2016 (UTC)

I agree with RexxS on all points mentioned above, but I am also willing to consider any carefully reasoned argument which takes into consideration the realities of industry standards and potential usefulness to the reader of all levels. • • • Peter (Southwood) (talk): 18:04, 5 November 2016 (UTC)

I know, most divers use the term "tank", which is incorrect usage, but we all know what they mean, and I use it myself simply because it doesn't sound as "geeky" as cylinder.
By CGA, PSI, DOT, and OSHA standards, all of which govern the scuba cylinder industry, a "TANK" is a permanently attached vessel.  A "CYLINDER" is a portable, mobile vessel.   For example:  My RV burns LP gas.  It has a TANK that is mounted to the vehicle frame.  It can't be easily removed and is considered to be an integral part of the vehicle. When I get ready to fill the tank, I drive to the truck stop and fill the RV tank up with LP gas.   
A forklift that runs on LP gas uses a CYLINDER.  It's strapped onto the back of the forklift, and when it's empty, I don't take the whole fork lift to the gas station.  I take the 30 lbs cylinder off and just replace it with a full one that's stored in the supply room.   When they're empty, I throw them on the back of the truck and go get them filled.
My gas grill uses a 20 lbs CYLINDER.   When it;s empty, I take it off and go have it filled.  I don't take the entire grill with me to the fill station.
A car has a fuel TANK.  It isn't detachable.
Since I'm PSI/PCI certified, I go by their terminology when in formal conversation.  Hanging around the dive shop It doesn't matter, tank or cylinder's is all the same to most people. — Preceding unsigned comment added by 71.51.248.75 (talk • contribs) 

It is not clear what point you are trying to make here. Cheers, · · · Peter (Southwood) (talk): 07:47, 13 June 2018 (UTC)

Anthony Appleyard, I reverted your recent edits which had some problems I was unable to fix.
You added:

As at early 2019, scuba cylinders can be got for higher pressures:
300 bar:
350 bar:
400 bar:
At high pressure, the simple ideal gas law (
  
    
      
        P
        V
        =
        n
        R
        T
      
    
    {\displaystyle PV=nRT}
  
) cannot always be relied on exactly. For more information see Van der Waals equation#Equation and this link.

Firstly, 300 bar cylinders have been available and in use since the 1980s, so not new.
The Google search links provided in lieu of references failed to provide me with any reliable evidence that 350 bar and 400 bar working pressure cylinders are available for legal scuba use. This does not necessarily mean that they do not exist, but it demonstrates why such links are not suitable for use as references. There is no guarantee that the user will be able to find the information, not even which of the search results is most likely to be worth examining in detail. I checked a few. Most of the results referred to non-scuba service or to test pressure, not working pressure. If you found a site which actually shows 350 and 400 bar working pressure cylinders available for scuba service, please at the very least link to that specific page, not the search, and preferably provide a properly formatted reference to whichever accepted style you prefer, not a bare url, which is more susceptible to linkrot.
As we have not established whether these higher pressure cylinders are actually available, is it necessary to go into van der Waal's equation? (or any of the other non-linear gas equations for higher pressures)? I will look into linking to relevant Wikipedia articles, but we do not use inline links to external websites in the body of a rated "good article". Cheers, · · · Peter Southwood (talk): 16:02, 1 February 2019 (UTC)
What cylinder valves and regulators would be used on higher pressure cylinders? I do not know of any rated for more than 300 bar. · · · Peter Southwood (talk): 16:52, 1 February 2019 (UTC)
I have modified Diving_cylinder#The_cylinder's_capacity_to_store_gas to mention the limitations of the ideal gas laws and a link to the Van de Waals equation. I will look into getting a graph to illustrate the difference. · · · Peter Southwood (talk): 16:48, 1 February 2019 (UTC)

@Pbsouthwood: Thanks, sorry. Anthony Appleyard (talk) 17:08, 1 February 2019 (UTC)

I have to agree with Peter's points about linking directly to websites rather than Google results per Wikipedia:Search engine test #Search engine tests and Wikipedia policies.
Tangentially, the theory behind non-linearity of gases under compression isn't really relevant to diving cylinders. It's enough to note three empirical results (for air or nitrox):
a cylinder at 300 bar will contain roughly 10% less free gas than an ideal gas would;
a cylinder at 232 bar will contain roughly 5% less free gas than an ideal gas would;
a cylinder pressurised to less than 200 bar will not deviate significantly from the ideal gas law.
That's off the top of my head, so I'll have to go and find a reliable source for the figures if we want to use them, but that would be far more practical information for a diver than a link to the Van der Waals equation article. --RexxS (talk) 17:18, 1 February 2019 (UTC)
Or you could calculate the difference between ideal and v d Waals values for those pressures:-) Actually a graph would say it all. It is more of a problem for partial pressure blending to high pressures, but that would be more at home in gas blending for scuba diving, if not already mentioned. I will check. · · · Peter Southwood (talk): 20:27, 1 February 2019 (UTC)
I added a bit in gas blending. · · · Peter Southwood (talk): 20:27, 1 February 2019 (UTC)

Hi. I am going through Good Articles with clean up tags on them. Currently we have an expand section tag under the "Surface finish, colour-coding and labeling" sub heading asking for more info on  Refinishing, problems with powder coating aluminium, corrosion under attachments etc.. Looking at the article we are sitting at 68KB readable prose. We are into the probably should be divided territory (and considering this is an article on one piece of Scuba equipment an argument could probably be made that it falls short focus wise). Anyway I was wondering whether we really need more info on surface finish. From a bigger picture point of view, has there been any thought to splitting this? AIRcorn (talk) 09:34, 20 January 2020 (UTC)


### Proposed split
Aircorn, I have been considering splitting out the content on valves to scuba cylinder valve. · · · Peter Southwood (talk): 19:35, 22 March 2020 (UTC)
Sorry for late reply. I would encourage any splitting you see necessary here to keep this more aligned with summary style. AIRcorn (talk) 03:38, 17 April 2020 (UTC)
Better late than never. I will try to remember to get round to it soonish. Splitting out Scuba cylinder valve would remove about 18KB, but the summary would put a bit back. Cheers, · · · Peter Southwood (talk): 09:59, 21 January 2021 (UTC)
 Done · · · Peter Southwood (talk): 15:50, 21 January 2021 (UTC)

It has been a while since this article has been reviewed, so I took a look and noticed the following:

There are a lot of uncited statements, including entire paragraphs.
At almost 13,000 words, this article is too detailed and WP:TOOBIG. Can any information be spun out, summarised more effectively, or removed as too much detail?
Should this article go to WP:GAR? Z1720 (talk) 22:54, 1 July 2025 (UTC)


### Diving cylinder
As usual, I am willing to address any problems that are clearly and specifically identified, and reasonably practicable and actionable recommendations made for improvements. Cheers, · · · Peter Southwood (talk): 16:17, 9 July 2025 (UTC)

As is obvious from basic materials science/mechanical engineering, a cylinder will expand when pressurised and contract when depressurised "The decrease in external volume of the cylinder due to reduction of internal pressure is relatively small, and can be ignored for practical purposes." Volumetric expansion during hydrostatic testing is in the order of 1%, and varies depending on cylinder geometry and material, so expansion/contraction from normal use is order of 0.5%, but I don't have a citeable source - the information is from hydro test techs, pers com. so have removed it from the article and leave it here in case someone can provide citeable data. It must be out there somewhere. Cheers, · · · Peter Southwood (talk): 13:48, 16 July 2025 (UTC)

Found a video on YouTube with a typical example of an Al80 tested to 5000psi which expanded 73.6cc so expansion would be 3/5 of that (44.16cc) at 3000psi. That is a change of buoyancy of 44 grams (0.097 lb) if the entire gas contents were used during a dive, which is small compared to the weight loss, and can be disregarded as a first approximation. · · · Peter Southwood (talk): 04:39, 29 July 2025 (UTC)