Please Educate A Newbie on Nitrox :)

[Herk_Man]

+1 on feeling less fatigued after diving Nitrox (actually +4 since my whole family agrees.)

And even if your SAC rate doesn't allow you to benefit from the increased bottom times available with Nitrox, you will benefit from shorter surface intervals.

It's a great cert to have. Just make sure you know the few dangers it presents.

 

[Peter Guy]

Price -- It is worth what you get out of it. Me, I charge $100 for my class (materials NOT included and no dives) and the class takes about 6 hours of lecture/discussion.

What should be in the class:

In my opinion, a good Nitrox class will cover:

a. Benefits (discussed at length in this thread);

b. How it is created (you should actually see how Partial Pressure Blending and Continuous Blending are done so you have an understanding of WHY the rules regarding "O2 Cleaning" are written as they are);

c. Gas Management -- As this is seldom taught in most OW classes (And YES I KNOW it is taught in "the better" ones) the EAN class should cover it because you will be doing more dive planning as part of your EAN class. PLEASE make sure your instructor includes this segment in his class.

d. Decompression Theory and Practice -- As Nitrox is used "to extend NDLs" you should be getting deeper into Deco Theory and Practice so that you can understand WHY EAN "extends NDLs"

While this may not be the standard class, I hope you can convince your instructor to cover these points in addition to the stuff covered in the text -- whatever agency you may be using.

 

[muddiver]

That's expensive IMO. Nitrox use is so easy and simple that it should be a low online course fee, that's it. Try to get a nitrox certification bundled with some other training for a much-reduced price. It's not that hard to do, and since there's almost no skill involved, the teacher is not nearly as important as with a more involved skill class.

If the shop told you that nitrox increases bottom time AND increases safety, maybe they need to take the class again. It can increase bottom time, and theoretically it can reduce DCS risk, but it does not do both. I bet someone has already brought this up in this thread.

It's very important to understand that nitrox has not been shown to decrease DCS risk in recreational diving. Making incorrect assumptions about safety is in itself an added risk, as it is likely to affect dive behavior at some point.

Regarding the fatigue issues, I have found that extending safety stops and practicing very slow ascents from the stop also reduce fatigue, particularly on multi-dive days. I believe the fatigue (this is a theory, not a fact) is mostly due to residual N2 loading, so lowering your N2 through any means 'should' have the same effect.

Nitrox is very useful for liveaboards and other multi-dive trips, as it does really increase your ability to do many dives to substantial depths in a given day and stay below NDL. For a two-dive day it probably won't affect your dives much, especially if you're in a group with both air and nitrox divers diving together with the same profile.

You need to back up your statement. The pysiology and dive medicine alone is enough proof to me that breathing elevated percentages of oxygen duing any dive will reduce the risk of DCS by limiting the speed and amount of Nitrogen uptake by the body. That is also why using oxygen enriched air extents the NDLs when compaired to an air "No D" diving table.

I agree that the prices quoted are high. I just checked the largest shop in Southern California and they are priced around $99 for the course with books.

 

[TSandM]

The pysiology and dive medicine alone is enough proof to me that breathing elevated percentages of oxygen duing any dive will reduce the risk of DCS by limiting the speed and amount of Nitrogen uptake by the body. That is also why using oxygen enriched air extents the NDLs when compaired to an air "No D" diving table.

Using a gas with a higher oxygen content means using a gas with a lower nitrogen content, by definition. Lower nitrogen content in the breathing gas means less absorbed nitrogen per unit time at any given depth. HOWEVER, there is plenty of nitrogen in recreational Nitrox to saturate you beyond a safe, direct ascent . . . in other words, it is quite possible to exceed NDLs FOR Nitrox, ON Nitrox. At this point, you have no greater safety than you would if you had done the same thing on air.

If you do a 30 minute dive to 70 feet on air, or the exact same dive on Nitrox 32, you will have less nitrogen in your tissues after the Nitrox dive. In theory, this should mean that your risk of DCS on that second dive is lower. But that's not what most people do. They do their NDLs on air, and they do their (increased) NDLs on Nitrox. In both cases, you have absorbed as much nitrogen as you safely can for that dive, and neither dive is "safer". One may have been quite a bit longer, though . . .

 

[halocline]

You need to back up your statement. The pysiology and dive medicine alone is enough proof to me that breathing elevated percentages of oxygen duing any dive will reduce the risk of DCS by limiting the speed and amount of Nitrogen uptake by the body.

You're talking about a theory, which is certainly based on solid arguments. But for something to be proven "safer" or proven to "reduce risk of DCS" you would need clinical studies that show a reduced incidence of DCS with recreational nitrox use. As far as I know, such a study does not yet exist.

I agree with the logic that, all other things equal, breathing a gas with lower N2 content will result in less N2 loading, and consequently SHOULD reduce the risk of DCS. But that's different that proving that using nitrox does in fact make one less likely to get DCS.

But, my post was emphasizing that if you use nitrox to increase bottom time, the theoretical additional safety margin is either diminished or lost.

 

[ScubaFeenD]

You're talking about a theory, which is certainly based on solid arguments. But for something to be proven "safer" or proven to "reduce risk of DCS" you would need clinical studies that show a reduced incidence of DCS with recreational nitrox use. As far as I know, such a study does not yet exist.

I agree with the logic that, all other things equal, breathing a gas with lower N2 content will result in less N2 loading, and consequently SHOULD reduce the risk of DCS. But that's different that proving that using nitrox does in fact make one less likely to get DCS.

But, my post was emphasizing that if you use nitrox to increase bottom time, the theoretical additional safety margin is either diminished or lost.

It only makes sense if you compare two people who are each using one of the gases, and staying on the gas at the same depth. With nitrox there are still NDLs, because eventually, even with nitrox, you load your tissues with nitrogen.

 

[String]

In theory, this should mean that your risk of DCS on that second dive is lower.

Theory. No statistically significant decrease has ever been found. It could easily be one of these things that has a theoretical reduction but no real world effect or something so small its masked by every other factor.

As for "less fatigued" again no evidence to suggest that. If those claims are true you'd expect a direct correlation between depth and tiredness for a particular gas as it is only the nitrogen loading that could affect that. Again no such evidence exists.
Do people really claim they feel more tired after a 20m air dive than a 10m air dive? If not why do people claim to be less tired at a certain depth on nitrox vs the same dive as air? There is absolutely no scientific basis for that as if its N2 loading then the above would also be true.

 

[TSandM]

I agree -- it has never been shown that the use of Nitrox reduces DCS risk. But as I stated before, it's not because Nitrox doesn't reduce nitrogen loading for the same depth and time. It's because people who dive Nitrox USE the increased bottom time it permits, so nitrogen loading is essentially equivalent. Given the low prevalence of DCS to begin with, and the MANY variables involved in diving (depth, time, exertion, temperature, diver fitness, etc.) it would take a HUGE database to be able to identify even a significant difference in safety.

 

[String]

But as I stated before, it's not because Nitrox doesn't reduce nitrogen loading for the same depth and time. It's because people who dive Nitrox USE the increased bottom time it permits, so nitrogen loading is essentially equivalent.

Again though even for that to be true you'd expect people to claim they're more tired the longer they dive at a specific depth on a specific gas and ive never seen anyone make that type of claim.
If its entirely about N2 loading someone doing a 10min dive to 20m on air should be reporting less fatigue than when they do 20 or 30 mins to 20m on air. That doesnt seem to be the case which blows out of the water claims that its N2 loading that causes fatigue or nitrox helping it.

However the sub-clinical DCS/fatigue issue which can be mitigated by doing slow ascents, eliminating sawtooth profiles, extending safety stops and so on does have some sort of scientific basis but thats completely separate from the nitrox vs air issue.

Given the low prevalence of DCS to begin with, and the MANY variables involved in diving (depth, time, exertion, temperature, diver fitness, etc.) it would take a HUGE database to be able to identify even a significant difference in safety.

Yes so nobody can claim there is one. If the difference is that small all other real world effects mask it then its a non-issue.

 

[brucet]

I personally use a 130 steel with Nitrox for deeper dives. I wanted the longer bottom time. I say take the class, but shop around. I did mine with SDI online, for $95 about a year and half ago.