Benefit of Nitrox?

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Here's what seems reasonable to me:

  1. The typical recreational diver exhibits fairly lax skills and techniques; saw-tooth profiles, reverse-profile repetitive diving, relatively rapid ascents, short SI's, generally poor buoyancy skills, pushing NDLs, and has at best a rudimentary grasp of dive planning, tables, or their dive computers
  2. Lax diving skills - while unlikely to put the typical recreational diver in a chamber - are likely to produce sub-clinical DCS or so called "silent bubbles" in the blood stream and body tissues
  3. The silent bubbles from sub-clinical DCS that are experienced by typical recreational divers with lax dive skills are likely to produce symptoms of fatigue
  4. Accordingly typical recreational divers with lax dive skills who dive nitrox will experience less bubbles, and therefor will experience less fatigue secondary to the sub-clinical DCS they ordinarily experience when diving on air

But seriously, let's be more objective and consider it this way...


  • The data from well-controlled studies (eg all participants are placed in a chamber or otherwise subjected to exactly the same dive profiles relative to depth, time, ascent rate, etc which are controlled by the scientists conducting the study) show that divers using nitrox have no statistically significant difference in post-dive fatigue as compared to divers on air
  • Anecdotal "data" from poorly-controlled studies (eg: typical recreational divers jump in the water, do their own thing, and tell everyone "I feel better") suggest that those who dive nitrox are less fatigued than when they dive air
  • So it would appear reasonable to conclude from the literature that people who dive in a well-controlled fashion exhibit less fatigue than people who dive in a poorly-controlled fashion... irrespective of their choice of breathing gas.

I agree 100%.

Nitrox doesn't make you feel "better" after a dive. But it can make you feel "less worse" after a dive where you'd otherwise off-gas inefficiently.

If inefficient off-gassing has become a 'norm' to the diver, then nitrox might be identified with reducing 'normal' post-dive fatigue (that needn't exist in the first place).

This assumes that nitrox use causes decreased nitrogen on-gassing for the majority of divers, due to dives being limited by air-consumption not no-stop limits (i.e. nitrox use does not permit relatively longer dives versus significantly decreased rate of on-gassing).

The consequence of that decreased nitrogen on-gassing is less severe sub-clinical DCS symptoms (fatigue) following an inefficiently off-gassed dive/ascent.

I doubt DAN's dry-chamber studies mimicked 'common' inefficient off-gassing ascents and sub-clinical DCS (excessive micro bubbles) profiles.

Other things that make me feel decisively "less fatigued" after a dive:

1. Proper ascent rate at 9m per min until first stop (see 'best ascent speed').

2. Multiple safety stops at 9, 6 and 3m (e.g. ANDI ascent protocol).

3. Using an ascent gas (i.e. 40-50% O2) to off-gas more efficiently.

4. Proper ascent rate <3m per minute from first stop onwards.

For novice divers, in short, you shouldn't feel fatigued after scuba diving. If you do.... or if you notice nitrox 'reducing fatigue', then also consider analyzing and refining your ascent practices....
 
Nitrox doesn't make you feel "better" after a dive. But it can make you feel "less worse" after a dive where you'd otherwise off-gas inefficiently.

If inefficient off-gassing has become a 'norm' to the diver, then nitrox might be identified with reducing 'normal' post-dive fatigue (that needn't exist in the first place).
Absolutely. But then, every dive isn't a perfect dive -at least for the unwashed masses I belong to. I'll readily admit that I don't always dive perfectly and probably don't always off-gas as efficient as I could/should. Sometimes I get cold, and we know that that affects off-gassing negatively. Sometimes I have a little too much gas in my DS (to avoid becoming too cold), and I don't control my final ascent from my SS as well as I should. Non-ideal ascent profile. On occasions, I've felt the need to surface briefly to check on my navigation. Sawtooth profile. When the dive is finished, I have to schlep my gear myself, and my tanks are some 15kg each, empty without the valve. Physical exertion shortly after a dive is known to provoke bubble formation. None of this is particularly conductive to ideal offgassing. Give me two deep-ish dives (on air) in one day, even with good profiles and a decent SI, and it's not uncommon that I'm ready to hit the bunk around eight o'clock in the evening.

I'm middle-aged and my physical condition reflects that; I'm not as fit as I was in my twenties. I'm the poster-boy for increasing the conservatism setting on my computer, but then my dives would really be nitrogen limited, not gas reserve limited. Instead, I choose to dive nitrox when it's available (my club provides nitrox at a very reasonable cost). Bang, I'm well away from air NDLs and obviously less nitrogen-loaded. Instant conservatism. There's a reason they call it geezer gas.

Other things that make me feel decisively "less fatigued" after a dive:

1. Proper ascent rate at 9m per min until first stop (see 'best ascent speed').

2. Multiple safety stops at 9, 6 and 3m (e.g. ANDI ascent protocol).

3. Using an ascent gas (i.e. 40-50% O2) to off-gas more efficiently.

4. Proper ascent rate <3m per minute from first stop onwards.

For me:
5. Using nitrox on dives approaching air NDLs, particularly in cold conditions and/or on shore dives when I have to schlep my gear from the site up to the car.
 
I use Nitrox if it is on square profile(more or less) eg. wreck.
If I can do a multi-level dive then Nitrox 21 any time.

---------- Post added September 7th, 2015 at 01:29 PM ----------


If the deck of a wreck is at 30m, EAN32 is a lot better than EAN21. Because it does extend the bottom time.
But if the wreck eg. San Francisco Maru(in Truk) at ~52m then it is either AIR or Trimix.
For me, nitrox has only a small useful range. But it is definitely not gross waste of money and time.


I did qualify it with it was a gross waste of time and money for me. Maybe it wasn't for a waste for you but it was for me. I dive the U853 here in RI. It sits in 130FSW Unless I use my doubles I can't stay any longer with nitrox as I can with air because my SAC sucks. It's gotten better since my 1st dive in April 1968 but not good enough to benefit from longer BT using nitrox. Anyone who asks about nitrox will get the same answer from me. For me, AfterDark it was a gross waste of time and money. I used it 6 times realized I made a costly and stupid mistake and haven't used it since. That was 3 years ago. Three of my 4 O2 cleaned tanks are due for hydro. I'll be taking the nitrox stickers off before I send them out and will not request they continue to be O2 clean for nitrox blending. Good ole 21% for me until I retire from diving!

I'll add this: I wish there had been someone like me on SB 3 years ago posting what I've posted about nitrox. That poster would have saved me a couple of hundred dollars for training I didn't need (I could have taught the class) and O2 cleaning of tanks that was useless to me.

SO IF YOU CAN"T HIT NDLs WITH A SINGLE TANK DON'T DO NITROX. YOU WILL FIND IT A GROSS WASTE OF TIME AND MONEY.
 
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I have mostly used nitrox on liveaboard and have found it gives me much longer ndl times than those diving on air. I have quite low air use and ndls had become a limiting factor on some repetitive dives on air.
On a recent liveaboard I had a buddy diving on air while I was on nitrox. I had plenty of ndl time, she had hit deco twice (although excessively conservative suunto computer may well have contributed).




Wouldn't bother with it for shallow or non repetitive dives though.


Sent from my XT905 using Tapatalk
 
... I dive the U853 here in RI. It sits in 130FSW Unless I use my doubles I can't stay any longer with nitrox as I can with air because my SAC sucks.
130ft = ~ 40m
And if we keep the PPO2 to 1.4, the suitable nitrox would be EAN28. And the extra 7% of O2 won't make hell a lot difference on the ndl.
Nevertheless, anyone who is using AIR on this wreck will hit ndl sooner than EAN28.
 
130ft = ~ 40m
And if we keep the PPO2 to 1.4, the suitable nitrox would be EAN28. And the extra 7% of O2 won't make hell a lot difference on the ndl.
Nevertheless, anyone who is using AIR on this wreck will hit ndl sooner than EAN28.

Except me because I hit my turn around pressure before the NDL for 21%. Am I the only one with this situation?

---------- Post added September 7th, 2015 at 06:25 AM ----------

I have mostly used nitrox on liveaboard and have found it gives me much longer ndl times than those diving on air. I have quite low air use and ndls had become a limiting factor on some repetitive dives on air.
On a recent liveaboard I had a buddy diving on air while I was on nitrox. I had plenty of ndl time, she had hit deco twice (although excessively conservative suunto computer may well have contributed).




Wouldn't bother with it for shallow or non repetitive dives though.


Sent from my XT905 using Tapatalk

Nitrox is perfect for you. If your SAC is that low you'll get longer dives even for shallow or non repetitive dives.

People like me need surface supplied gas to benefit from nitrox. :(
 
Third dive of the day! I haven't done 3 dives in a day in 20 years! This thread just keeps reinforcing my regret at becoming nitrox cert.
Well it IS a tool for a purpose, although I doubt the extra knowledge exploded your brain :p

As to it being a "waste of money" to use nitrox when its "not needed" - that depends entirely on the supplier. Some provide it for the same cost as they provide air (typically not pp-blenders)
 
Don't you think that this statement is playing the reference of words a little to much????? It seems that even your wording says on a scale of 0-10,, 0 being bad and 10 being good nitrox gets a higher score on the feeling scale. GEEESH

MO BETTER OR LESS WORSE???????

I agree 100%.

Nitrox doesn't make you feel "better" after a dive. But it can make you feel "less worse" after a dive where you'd otherwise off-gas inefficiently.
 
since diving in Cozumel, nitrox, which seems to be the latest thing.

Others have summarized the benefits pretty well... increased bottom time at many depths, OR increased safety if you stick to air profiles.

It's not without it's risks however, which is why it's important to take the course.

The main reason I chimed in here though is to point out that diving Nitrox is not the "latest thing". The benefits of it's use are well documented and have been for a long time.. probably about as long as you have been away from diving!
 
Don't you think that this statement is playing the reference of words a little to much????? It seems that even your wording says on a scale of 0-10,, 0 being bad and 10 being good nitrox gets a higher score on the feeling scale. GEEESH

MO BETTER OR LESS WORSE???????

I think what he's saying is that Nitrox masks the underlying problem... when the better approach would be to FIX the underlying problem.
 
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