Is there any reason why two buddies can't dive together one using Nitrox and the other using air?
Air Nitrox buddies
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You can dive together. I've dove using Nitrox and my buddy on air. Since Nitrox allows for additional bottom time, the drawback is the diver using regular air will have to end his/her dive sooner (of course depending on depth and other factors). When it was time for him to come up, so did I even though I had additional bottom time remaining.
"can't"? No, no reason. Still, there are a two main things to keep in mind.
- The nitrox diver will have a MOD potentially much shallower than the air diver.
- The air diver will have NDLs potentially much shorter than the nitrox diver.
It is very important you set up your dive plans accordingly and stick to them. If you are diving in areas where you won't hit bottom, then the dive is limited to the MOD of the nitrox user. So setting depth limits is critical. You really need to make sure your buddy understands your limits. Plan your dive and dive your plan.
Happy Safe diving!
Carolyn:sharks:
Happy Safe diving!
Carolyn:sharks:
OP
Everything you guys are saying is been my point with my buddy. I prefer Nitrox, not so much to extend my bottom time, but to reduce nitrogen absorbtion. I am perfectly happy to dive nitrox MOD with an air bottom time. I have this buddy who is convinced that in an out of air emergency all hell will break loose if the Nitrox diver has to breath air or vice versa. I can't see the issue. But he wants something authoritative. You know of anything?
Damselfish
Contributor
maybe you can get him to take the Nitrox class for the knowledge, even if he doesn't want to dive it. Or at least get him to read your book so he understands it, even if he doesn't take the course officially.
Good heavens you asked the question on the internnets and got all of these answers, what more could he want!
That being said a small part of the nitrox course does deal with handling a dive buddy that has oxygen poisoning so there is a grain of truth in his concern. If he''s not in a position to take the course perhaps he could spend some quality time with your text. As you know the hands on part of the course is very slight, especially for the non user.
Pete
All hell would not in fact break loose.
I would suggest that the OOA diver log the dive afterwards with N2 loading based on having been on Air for the whole dive but also track O2 loading as if the entire dive had been done on Nitrox and track O2 for the remainder of the day. This gives a margin of saftey on both sides.
As for any immediate physiological effects, as long as the pair of divers is above the O2 toxicity level I can't think of anything bad that would happen while still on the dive.
As long as you're both willing to dive within the boundaries of the two individual profiles it shouldn't be a problem. Technical divers change gas mixtures all the time at depth without ill effects if that's what your buddy is worried about.
If the nitrox diver has to breathe shared air, what would that mean? Well, if he's diving on a computer set to his nitrox mix, he will be retaining more nitrogen than his computer believes. How significant the results of this become is related to time and depth, but he will never be worse off than the air diver with which he is diving.
The worst-idea scenario would be a high-O2 nitrox diver losing his air early in a dive and proceeding to make the dive to the NDL of the air diver (who must have some doubles or something to have all that extra air). If that diver was diving with a computer set to the nitrox mix, and if that diver follows a minimal surface interval with another dive to NDL given by his computer in nitrox mode the whole time, he subjects himself to an increased potential for DCS by virtue of having more N2 in his system than the computer believes.
If all dives in the series were with the air diver, and if any subsequent dives are also with the air diver, the nitrox diver will never approach the nitrox NDLs, and so, the inherent conservatism of diving with the air diver will be more than adequate to preclude any potential violations of the NDL that would have been computed had the diver had a computer capable of multiple gas switching. That mixed nitrox/air NDL *must* be between than the air NDL and the nitrox NDL, with the air NDL describing the lower limit.
On the other hand, if the air diver needs to share from the nitrox diver, what would we have? Well, obviously, MOD isn't an issue, as the nitrox diver is safely diving the mix. Nitrogen loading is also a non-issue -- actually, his N2 loading will be less than the computer believes, as it will be running with a lower O2 fraction. The only negative, then, is the increased oxygen exposure to the air diver.
Air computers don't even bother computing oxygen exposure, as it's just not a significant factor in recreational scuba diving. What small additional exposure the air diver will have from the nitrox sharing is irrelevant. Additionally, by virtue of having done the same dive(s), the nitrox diver will have *significantly* higher oxygen exposure than the air diver who had to share -- if he's well within limits, the air diver must certainly be even more so.
So, a nitrox computer diver breathing shared air will not have any problems with the given dive (since both divers are within the air NDLs), but he should be appropriately conservative if continuing a dive series if he had significant time on a poorer mix than that to which his computer was set. An air diver breathing shared nitrox will not have any problems (and will actually have somewhat reduced nitrogen loading compared to what his computer would indicate).
In neither case could sharing between air and nitrox divers cause any problems during the dive on which the gas was shared, provided the dive was within the air NDLs and above the nitrox MOD. The potential complications only apply to continuations of the dive series after the affected dive, and then basically exclusively to the was-nitrox-now-air diver.
(Well, that should be thorough enough, eh? For an air diver and a nitrox diver who dive together on the same series of dives, all within the air NDLs and the nitrox MODs, sharing air or nitrox *cannot* cause a problem. Only by exceeding the limits of one or both can you encounter a potential problem situation. It's simple logic, and as such, is indisputably authoritative. :biggrin
OP
I do appreciate your thoughtful and thorough responses (especially ClayJar). I understand the computer issues. But to tell you the honest truth, if one of us were to have an out of air emergency, I think we would call it a day for diving. And even waiting 24 hours (or more) wouldn't be to much to ask. I know the old saw about falling of the horse, but for me, regardless of which one of us it was who was out of air I don't think a day to calm down and reflect is unreasonable. My buddy is nitrox certified. I am not sure where this "all buddies must dive the same gas" belief system came from. But the guy is down right religious about it and we all know how effective arguing logic is with religious fanatics (no offense to any religious fanatics intended). I will try your logic, ClayJar, but I am afraid that if I can't find where "Jesus said it is so" I may just be shouting into the wind.
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