Do you think Nitrox is a deep diving gas?

[Blackwood]

From the PADI Enriched Air Diver Manual;
"the DCI incidence rate is already so low in recreational diving that simply reducing nitrogen is unlikely to produce a meaningful safety improvement. Although there's been no experimental study of this, statistical estimates suggest that using enriched air within normal air limits only reduces the incidence rate a fraction of a percent. There is some risk reduction (mathematecally) if you use enriched air within air no decompression limits, but probably not a realistic, significant safety improvement from a practical point of view."

That statement is equivalent to "diving within table limits is no less risky than diving to table limits."

However, PADI 'requires' three minute stops for any dive within three 'pressure groups' of a table limit (due I suppose to some greater perceived risk associated with diving near or at the limit).

Something hasn't been well thought through (surprise).

 

[Thalassamania]

Statistics prove that there has been no reduction in DCS cases when using Nitrox. Theoretically, you stand a better chance due to less nitrogen, but air tables and computers are so conservative that the risk of DSC is already low.

Well ... turns out that's not quite the story ... eh? More accurate might be: According to a non-peer-reviewed source, "statistical estimates suggest that using enriched air within normal air limits only reduces the incidence rate a fraction of a percent" when viewed in terms of the performance of their in-house tables.

That's rather a different statement. PADI's tables have some assumptions and procedures that would, in-point-of-fact, reduce the advantages of EAN use. The 3 min. mandatory "safety" stop that was patched onto the 60 fpm ascent rate reduces the statistical probability of DCS way down (assuming it is performed correctly). To make such a sweeping statement without reference to this fact is highly misleading.

As ptyx said, cost, availability and training are good arguments. The majority of dives I make are beach dives in less than seventy feet. I'm not going to spend more than twice the cost of air for those dives. When I make wreck dives I'm usually deeper than Nitrox allows, so I use 50% and 100% O2 for deco gasses.
The only dives I use Nitrox on are working dives such as net removal when I want to spend more time on the bottom with less deco.

From the PADI Enriched Air Diver Manual;
"the DCI incidence rate is already so low in recreational diving that simply reducing nitrogen is unlikely to produce a meaningful safety improvement.

Patent marketing and self congraulatory B.S. since the DCS rate in the recreational diving community is generally recognized to be ten times that (on a per dive basis) than that enjoyed by the scientific diving community which has a depth limit of 190 ft rather than the recreational limit of 130 ft.

Although there's been no experimental study of this, statistical estimates suggest that using enriched air within normal air limits only reduces the incidence rate a fraction of a percent.

That a by-guess and by-golly estimate, I don't see it as meaningful. Especially when you consider the source of the statement and what it is in reference to.

There is some risk reduction (mathematecally) if you use enriched air within air no decompression limits, but probably not a realistic, significant safety improvement from a practical point of view."

Of course there is risk reduction, mathematical estimates that we did twenty years ago, based on the old U.S. Navy 12 tissue model, suggested that that risk reduction was on the order of 4% to 12% for EAN-36 at 100 fsw for 25 minutes; and 8% to 16% for EAN-32 at 130 ft for 10 min. That's both realistic enough and significant enough to get my attention, but then I'm rather attached to bowel, bladder and sexual function ... not to mention ambulation.

 

[Tigerman]

Given the fact that I dont consider recreational limits "deep diving" I dont consider nitrox a deep diving gas. Since you cant dive as deep on nitrox as you can on air, Id say air is more of a deep diving gas than nitrox is. Nitrox is just a ndl extender

 

[elan]

But it does lead me to wonder what education the AOW people are getting if they think EAN mixes are for "deep" diving. Yes they are, of course, but with the caveats. Hmmm, maybe should be part of one of my lectures this week.

Nitrox is not required for AOW at least in PADI so it's not a surprise they might not konw it

 

[HowardE]

Even if you dive to 150 feet on 25% you still get a benefit. The same dive - on air with 20 minutes of bottom time requires almost 15 more minutes of decompression (if you use your back gas for deco)

Enriched Air Nitrox is a great tool.

 

[ivobj]

Basically Nitrox has 2 main uses, to extend you botton time within NDL or as a safety gas, which is using Nitrox, but within air NDL, this gives you an extra safety margin, good if you plan to go near NDL. If you consider deep within recreational limits, indeed is good to use Nitrox, with the proper calculations not to exceed recommended ppO2.

But as depth increases and with it ppO2, also does Oxygen toxicity, so it is not indicated for deep tech dives, but the more O2 you have in your mix for a certain depth, the less deco you should have, in this sense, usually you plan your gas to put the max O2, given the planed depth (max ppO2 varies among agencies, usually 1.6 for deco and between 1.2 and 1.4 in the botton), that can be even less than 21%, depending on planned depth.

 

[Thalassamania]

That statement is equivalent to "diving within table limits is no less risky than diving to table limits."

However, PADI 'requires' three minute stops for any dive within three 'pressure groups' of a table limit (due I suppose to some greater perceived risk associated with diving near or at the limit).

Something hasn't been well thought through (surprise).

Thre real point is that if you add a non-required three minute stop at ten feet to any set of no-decompression tables the probability of DCS drops so low that the difference between that table (so used) and an EAN dive to the no-D limit followed by an ascent (with or without such a stop) is so small as to be hardly worth mentioning. Now, if all O/W divers could actually hold a 10 foot stop for three minutes at the end of their entry level course we might have a meaningful discussion.

 

[Tigerman]

Thats why OW dont allow you to go so deep the NDL is an issue in the first place..
Atleast most fresh OW certified divers will run out of air before they get to the NDL (if they stay within the certified depths). 50 minutes on 18 meters fresh out of OW, with mediocre (at best) bouyancy control? I think not

 

[Thalassamania]

Thats why OW dont allow you to go so deep the NDL is an issue in the first place..
Atleast most fresh OW certified divers will run out of air before they get to the NDL (if they stay within the certified depths). 50 minutes on 18 meters fresh out of OW, with mediocre (at best) bouyancy control? I think not

Ah ... now I finally understand, you train incompetent, nervous divers so that their lack of comfort and high SAC rate keeps them from getting bent because they can't stay down long enough to really need to hold a safety stop. How ingenious.

 

[imwright1985]

When using nitrox you will find your "optimum bottom time" at approximately 90 feet of sea water. When you study a "nitrox chart" you will eventually come to this conclusion.

In recreational diving, 100-130 feet deep is considered deep diving. Given this designation, nitrox would not be considered a deep diving gas.

One of the benefits, often overlooked, of using EAN, at any depth, is the likelyhood of getting DCS is significantly reduced.

There are no good arguments for NOT using Nitrox.

yes there is im not nitrox certified yet. other than that and knowing the limits for the mixes your using nitrox is awsome