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What are the benefits of diving nitrox?


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#1 WreckWench

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Posted 22 September 2010 - 05:57 AM

I have been emailing a member about the benefits of diving nitrox. We've also been talking about ensuring his dives have reached the point where he is running out of bottom time rather than air/gas.

So how do know when you are ready to benefit from Nitrox? And can we create a list of all the benefits for this and other divers considering getting the certification? :wakawaka:

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#2 georoc01

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Posted 22 September 2010 - 06:53 AM

The #1 reason is because it reduces the amount of nitrogen absorbed by the body and can reduce the chance of a DCS hit.

#3 Landlocked Dive Nut

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Posted 22 September 2010 - 06:54 AM

The obvious benefit is less nitrogen uptake, which translates to reduced chance of a DCS hit.
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#4 WreckWench

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Posted 22 September 2010 - 08:27 AM

Can't beat two great minds thinking alike at the same time! :wakawaka:

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#5 JimG

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Posted 22 September 2010 - 08:37 AM

"Lowers Nitrogen absorption and (therefore) reduces the chance of DCS" - I do not agree with either one of those statements. If that is what Nitrox instructors are teaching these days, then it is clear to me that they do not really understand Nitrox.

It is true that diving to equivalent depths and times on Nitrox will result in less Nitrogen absorption than the same depths and times on Air. If that is what people were doing, then I would grant that the above statements might be true. In my experience however, that is not how most people are using Nitrox. The most common use of Nitrox (and the purpose for which it was developed) is to extend bottom time at a given depth, or to go to a deeper depth for the same amount of time. If a person dives to the limit on Nitrox, then they will absorb just as much Nitrogen as if they dived to the equivalent limit on Air. So from a practical standpoint, I don't see "lowers Nitrogen absorption" as a tangible benefit, given how Nitrox is typically being used.

With respect to DCS, the operational aspects of the dive have much more to do with increased risk than the breathing gas does. Divers who ascend too quickly or hold their breath while on Nitrox, will be injured just as surely as if they had done the same thing on Air. There may be some marginal reduction in the chances of DCS, due to "slower effective ascent rate", or to breathing higher PPO2 at the safety stop, but I am not aware of any studies that support this notion. So again, I see no tangible benefit to using Nitrox for the sole purpose of "reducing DCS risk".

Nitrox is not some panacea that will automatically reduce risk of a diving injury. As divers, we all have the responsibility to follow safe diving practices, and the standard safety recommendations always apply, independent of the breathing gas - do not push the limits of your table or computer, always ascend slowly, and do safety stops on every dive. These things will reduce the overall risk much more so than the choice of breathing gas.

To answer the question that Kamala posed, I see the primary benefit of Nitrox as extending bottom time, for divers who have good enough air consumption to take advantage of it. And I guess I see some benefit to diving Nitrox on Air profiles where certain risk factors may be present (cold , etc). There is also some anecdotal evidence to suggest that divers "feel better" after Nitrox dives than after Air dives, probably due to reduced partial pressures of Nitrogen during the dives (my own experience diving with Nitrox bears this out).

But I don't really see "lowers Nitrogen absorption and (therefore) reduces the chance of DCS" as being applicable to most Nitrox dives, insofar as how most divers are conducting them.

(Sorry if I came on too strong with this post - this is a hot button topic for me, and I guess I get kind of crabby when I see people referencing these particular "sound bytes". :wakawaka:)

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#6 Landlocked Dive Nut

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Posted 22 September 2010 - 08:54 AM

Yes, they do teach this in Nitrox class, Jim, although my statement was simplified. I was also taught that I should dive shallower when diving Nitrox, due to oxygen toxicity issues (I dive a conservative 1.4 PO2, and typically stay well above the 100 foot level on Nitrox). I would not have limited myself this way diving on Air. So my statement about lower Nitrogen uptake refers to how i dive personally, and I believe it holds true. (I'm not trying to push your hot button, Jim!) :wakawaka:

Due to typical dive operation restrictions (no more than 1 hour bottom time per dive), I get the same amount of bottom time on Nitrox as I did on Air, and I do not max out the oxygen uptake even on my conservative dive computer, and I never go into nitrogen deco.

I do feel less fatigued after a week diving on Nitrox as compared to the same week of diving on Air. I don't know the science behind why I feel less fatigue, but at my age I DO notice the difference.
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#7 JimG

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Posted 22 September 2010 - 09:03 AM

Just to clarify, when I said "dive deeper for the same time" I was not talking about exceeding the MOD for the mix. I am pretty conservative on my MODs as well (around 1.3), and 100 feet is pretty much my absolute depth limit for any dives on Nitrox or Air. What I had reference to with the "dive deeper" comment is that you could do a dive to (for example) 60 feet on EAN32 or EAN36, while observing the longer NDLs for a 50 foot dive.

LLDN, if you are diving as you describe, then I agree that you are probably reducing Nitrogen uptake (and therefore risk). However, you are the exception rather than the rule, at least in my experience.

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#8 Landlocked Dive Nut

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Posted 22 September 2010 - 09:07 AM

:D Yes, I am exceptional! :wakawaka: :birthday:
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#9 scubajunkie6

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Posted 22 September 2010 - 09:09 AM

I do feel less fatigued after a week diving on Nitrox as compared to the same week of diving on Air. I don't know the science behind why I feel less fatigue, but at my age I DO notice the difference.


LLDN, I feel the same way. I've always felt that I can stay down longer without being as tired (also diving less than 100 feet), and perhaps more importantly, I'm ready to go back in the water sooner! :wakawaka:

#10 Parrotman

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Posted 22 September 2010 - 10:37 AM

I have read studies that say that there is no basis to the claim that Nitrox makes you less tired after a dive however I also feel the same way. I am less tired after a dive and also at the end of a long dive trip with multiple dives. As for the bottom time. I rarely go below 100 ft any way and I can not remember the last time that I ended a dive because of how much gas I had left or the fact that I had reached my max bottom time. As Tammy said, most dive ops have a much more conservative dive time restriction than what I am able to do while staying within the parameters of my computer and my air consumption.

I have been told that if a person is only going to do a few dives over a few days that there is really no reason to do Nitrox. That the biggest benefit comes from the multiple dive scenario such as on a live aboard. While the Nitrox can extend your bottom time as it pertains to depth. In reality does it really extend your overall bottom time? In other words, using JimG's example you can do 60' for the time based on a 50'NDL dive but at the deeper depth you are going to be using more gas so in most cases would you really get longer bottom time or just longer time at depth?
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#11 Landlocked Dive Nut

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Posted 22 September 2010 - 10:44 AM

Not very scientific (sorry!), but you see football players sucking on the oxygen mask after a relatively short run of 100 yards or less. I think their muscles may be screaming (lactic acid buildup?) and oxygen helps.

Maybe the same concept applies to us older divers, and breathing a higher oxygen content gas??? Just a random thought....
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#12 peterbj7

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Posted 22 September 2010 - 10:50 AM

I started diving nitrox way back while PADI were still calling it "the devil gas". From the middle of England I had a 3+ hour drive to the south coast, often having to arrive in time to park, load gear etc for a 7:30am departure. After a long day out on the water, usually diving a deep (45-50mtr) wreck several hours offshore, then after lunch doing a "shallow" (15-25mtr) dive on a reef, then after a get-together in a pub back on shore I would often start my return drive around 9pm. When I was using air I would often find myself falling asleep at the wheel, and when I got home all I could do was lock the car and fall directly into bed. When I started diving nitrox all that changed - I had a safer drive home, and once there emptied the car and rinsed all my gear before having a shower and going to bed. A profound difference. I am in NO DOUBT that diving nitrox makes most divers far less tired.

As to safety, I find most divers fall someway between the two extremes, so they both have rather longer dives AND absorb less nitrogen than they would have with the same dive on air. So I do believe there is in practice a DCS safety benefit, though I wouldn't sell that as the reason for using nitrox.

#13 Racer184

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Posted 22 September 2010 - 12:33 PM

1) Shorter surface intervals ! Way shorter surface intervals. Really really short surface intervals. Change your tank and drop back in kind of surface intervals. Like... next time bring a book to read while waiting on the others' surface intervals kind of surface interval.

2) I know all the books say that nitrox will not make you feel better. But my head and body ignore the books. I feel GREAT when I get back on the boat.

#14 gobie

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Posted 23 September 2010 - 06:24 PM

wow!!!
Thank you everyone for the input. It sounds like i should definitely consider the nitrox, especially since i'll be staying a full 7 days in cozy.
My dive computer says that i shouldnt use it for nitorox diving. Is that true? Will it give me incoorect reading? Do i need a dive computer especially for nitrox? Wont i just be a getting an ultra conservative reading if i use the computer?

#15 scubaski

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Posted 23 September 2010 - 06:29 PM

You need a nitrox computer, should be able to find for $250---> $1500.00, Put a bid in for 1 of the Cochran's that WW usually have on the trips. Try it out and buy later...
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