BTW, legal niceties in the U.S, the UK and some other countries may preclude the automatic administering of oxygen, which is both a scandal and a tragedy, so please be aware of these legal niceties. But personally I'd go for the O2 bottle all the same ... First time, every time when there's a high likelihood of DCI.
It may be true that legal nicities may prohibit the automatic "administering" of O2...
BUT, I am aware of NO legal stricture preventing someone from choosing to breathe a breathable gas (not a pharmaceutical product), on their own initiative, on the surface.
This is a very important distinction, although it turns on legal definitions of what is and is not in a given bottle, and who does what.
For example in the US there are three commonly-available grades of O2 (ignoring the analytical grades) - welding, aviator's breathing and Oxygen USP.
Only the latter is regulated by law.
The first is avaialble for use in welding, as you'd suspect. But what you might not suspect is that impurities in welding gas will cause defective welds, even at extremely low contaminent levels, and defective welds can KILL people. As such welding O2 is actually
more pure than "Oxygen USP", by definition, and is, in a pinch, perfectly ok to consume.
The second, Aviator's breathing O2, is
intended for human consumption. It's intended purpose is for breathing in unpressurized aircraft cabins; many pilots use it at night above 5,000 feet or so, as visual acuity is important and is affected by even mild hypoxia, and over 10,000 feet it is essentially mandatory to use it. Private pilots generally use a cannula system and very low flow rates, as all they are attempting to do is provide some supplemental O2 in this situation - no a complete breathing supply. Its "big deal" from a purity perspective is that it must be extremely dry (low dewpoint), because unpressurized aircraft areas can be cold at altitude, and a frozen regulator (internal parts) could result in a disaster.
It is available without legal restriction in the United States, and may be consumed without restriction, subject only to the limits of your wallet. It can be had in basically any reasonably-sized town or city by the "K" or "T" bottle, quite inexpesnively (I pay $16 per "K", which is enough for 20-30 tanks of Nitrox.)
Most dive shops use this grade for blending Nitrox (and Trimix where appropriate.)
Oxygen USP is "medical grade." Its claim to fame is that it requires a prescription to dispense or administer, and/or "training" (e.g. EMS folks, etc) This is the stuff that you cannot buy and consume without a prescription. There are also strictures on putting anything other than it in a bottle labelled "Oxygen USP" (federal law on manufacturing of a prescription drug!), etc.
So..... if you come up from a dive, and feel you've blown your intended profile, your options are nowhere near as limited as you might think,
provided whoever you are diving with has half a brain and is not playing doctor-style games.
BTW, "doctor-style" games extend to "hyperbaric physicians" - that includes DAN - unless you question them CLOSELY (at which point they freely admit that their "doctor games" are, in fact, driven by the doctor stuff and not the dive physiology reality.)
If they have Aviator's Breathing O2 on board, irrespective of what kind of bottle it is contained in, if you have a means of breathing it you are free to grab and consume it (legally-speaking), since you are not "administering" anything - you are consuming a freely-sold breathable gas.
If that bottle contains Oxygen USP (and is so labelled) then
legally one should be "O2 provider certified" to "administer" it, whether to one's self or others, and legally doing so may trigger a whole chain of "standard of care" requirements (again, depending on who's doing it and what their relationship is to you.)
The distinction here is not minor.
If you have ABO on board a boat you are on, and desire to breathe it, the only restriction you have on doing so is the cost of the gas fill to recharge the bottle - and that cost is MINISCULE. Even if you PAY a dive shop to refill the bottle, it should not cost more than $10 - and that's at their usual 500%+ mark-up. Anyone who believes they may be at enhanced risk of a DCS hit and who does
not grab the bottle and consume it in such a situation
is, IMHO, a fool.
The difference in "wash-out" rates between breathing air and pure, 100% O2 on the surface is
very significant. It is
quite likely that you may avoid a hit you would otherwise take, and if you don't you are almost certani to lessen its severity, by consuming the O2.
The generally understood protocol on my personal (not-for-hire, non-charter, privately operated) vessel is this:
1. I have two full Jumbo-D bottles of 100% Aviator's Breathing O2 on board. These bottles DO NOT contain a prescription drug - they contain a breathable, human-safe consumable gas.
2. Divers often use such gas for decompression at depths at or under 20'. "The surface" is a depth of less than 20'. All dives are in fact decompression dives - we just usually do our deco on the surface, in what we call a "surface interval." Ergo, it is perfectly appropriate to breathe that decompression gas while on the surface, tempered only by its cost, which is not zero.
3. The bottles are in a Pelican box, in a cabinet on the boat, are clearly labelled, along with the appropriate regulator and demand valve, much like a scuba second stage. With the exception of connecting the hose to the demand valve, the kit is left assembled on the first bottle with the tank valve turned off.
4. If you have
any reason to believe you may need this gas to decompress on the surface, you may consume the gas contained in those bottle(s) on your own initiative. If you do not know how to put the hoses on to accomplish this, physical assembly of the kit is simple enough to show you in 30 seconds or less.
Neither I or anyone else - unless someone on the boat happens to be an EMT-trained person (there are a few I dive with) will "administer" O2 to anyone who is conscious and breathing - but you are free to consume any decompression gas on board the boat, or the surrounding air, you feel is appropriate for yourself, in your judgement. This includes a tank of Nitrox if you happen to have one and wish to use it in the same fashion. This covers "permission" to use these two tanks of breathable gas I have on board - if you would like to use someone
else's, please ask first (since its their property.)
5. I have
no Oxygen USP on board, and as such there is no "prescription or drug" issue with any of the gas(ses) I do have.
6. If you are UNconcsious I will do everything I am able to in order to attempt to save your life. The law provides that I do not have this duty, but I do have this right. Since if you are effectively drowned I cannot kill a dead person, there is no downside to this to you, and there may be a potential upside (I might save your azz.) Feel free to do the same to/for me if you desire if I'm the one in trouble.
7. If you tell me that you think you may be bent or suffering a diving-related injury (e.g. AGE, etc), or if I observe signs and symptoms consistent wth you being bent and upon close questioning you do not deny the possibility, I will alert the USCG on the radio, call DAN if in cell phone range, and endeavor to deliver you to the care of qualified professionals in the most reasonable fashion under the circumstances. I will also urge you to breathe the aforementioned decompression gas until you can be so transferred.
The unfortunate reality is that most "commercial" operations either cannot or will not operate under these kinds of understandings.
I do wonder sometimes how many people get bent following a charter boat dive who (1) knew they did something silly during it, and (2) did not grab the O2 bottle because of the stigma and hassle, along with possible cost of activating EMS for what they thought was a relatively low risk excursion "over the line."
IMHO the use of O2 - not as a "drug" but as a breathable decompression gas - should be
encouraged if a diver has
any reason to believe they have violated their intended profile and put themselves at enhanced risk of a DCS incident.
