Nitrox Certification?

[serambin]

What???? Oxygen is more narcotic than nitrogen???? You sure about that?? Check these links out:

http://www.dansa.org/medical/narcotic.html ("However, oxygen is significantly less narcotic than nitrogen ...")

Narcosis elimination is not one of the benefits of nitrox????

Are you talking about toxicity?

Have head theory that unmetabolized oxygen may be as narcotic as nitrogen but recreational divers don't usually subject themselves to oxygen pressures where this could be factor ... right?

The big difference is that you do metabolise O2, but not N2. I am getting a cert in EAN because at my age (54) using less nitogen at relatively shallow depths is easier on me than more n2. I will not dive - deeper, nor in most cases longer, but I will dive with less impact on my body (I hope).

At this point in the history of SCUBA, you can't say for certain what effects maximum NDL of nitrogen does to the body. You can't say there is no long term impact. You can't say, if you're over 50, add an extra 10 feet to your debth on the tables to compensate for your age. It just hasn't been studied that well.

So for me, the less small bubbles of n2 I have the better.

Stan

 

[Canadian_Diver]

Currently that claim isnt a sensible one to make. Even though common sense would dictate less nitrogen is good, latest research (including DAN) showed the % margin was so small as to be statistically insignificant.

There are various reasons for this including the fact standard tables for recreational diving are very safe but there was no measurable improved safety margin when people investigated it despite this going against what would seem logical - the effect is tiny.

Add that to the fact nitrox costs 3-4x that of an air fill here there are quite a few reasons why its not used exclusively.

I'd be interested to see this DAN article. I just did a search on their site and couldn't turn the article up. Can you send me a link? Intriguing indeed!

 

[Canadian_Diver]

There is no added safety from DCS if you extend your bottom time. This goes to the comment about the recent research being marginal. If you stay at depth longer than you would have on air... then the added safety from a higher percent of O2 in the mix goes away. You would have this benefit only if you dove Nitrox as if it were air... and returned to the surface without using your extended bottom time.

Ken

No one said you would extend your bottom time AND get an added safety margin from Nitrox. It would be one or the other.

The whole point is to decide before the dive how you're going to use the Nitrox. If you don't extend bottom time and dive it as you would air, the theory is that you have built additional padding into your nitrogen loading.

 

[Canadian_Diver]

I will admit that if I'm diving in an underwater reef park, in the caribbean, with no current and a maximum depth of 30 fsw ... nitrox would be an overkill. Hell, I'll probably just use a 40 foot snorkle ...

Amen.... or a garden hose.

 

[BarryNL]

Another advantage is a)) You'll have to refresh your knowledge of dive tables if you haven't been looking at them recently b) You'll get to understand a little more about dive physics particularly if it was a subject poorly covered in OW.

Of course, you could just download the US Navy dive manual from the net which covers the physics a lot better than any PADI course.

 

[DiveGolfSki]

Most science would disagree with that:

http://www.techdiver.ws/trimix_narcosis.shtml

http://www.divefortyoung.com/whatisnitrox.html
http://www.iantd.co.uk/IANTD/pages/TA Kev Gurr.htm

...Given the latest thoughts about mechanisms for narcosis oxygen indeed should be as or more narcotic than nitrogen as well.

Thanks String for all those links ... learn something new everyday. Oxygen is more narcotic than nitrogen. So why bother? Why bother with nitrox, heliox, trimix? You've made the case succinctly that: the safety margin claim isn't sensible (post #53), oxygen is more narcotic than nitrogen and it's too expensive.

av8er23, as we say in NY ... forgetaboutit! Don't bother with the Nitrox course. You'll get narced and DCS anyway but you'll save some money using AIR.

Of course, there is also IANTD's statement that "Oxygen is potentially twice as narcotic than Nitrogen. The upside being that at the partial pressures of oxygen within which we normally operate (0.21 to 1.6), oxygen narcosis is not a relevant issue. "

av8er23 you got a lot of reasons on this thread to take the Nitrox course and a lot of science thrown in for free. That alone should be incentive to take the course (i.e., further your knowledge).

 

[String]

Thanks String for all those links ... learn something new everyday. Oxygen is more narcotic than nitrogen. So why bother? Why bother with nitrox, heliox, trimix? You've made the case succinctly that: the safety margin claim isn't sensible (post #53), oxygen is more narcotic than nitrogen and it's too expensive.

Why bother is because for the same theoretical risk you can get longer bottom times with nitrox (and if using rich mixes significantly lower time spent on deco). There was not found to be a statistically significant decrease in risk diving it on air tables as a safety margin but that sidesteps the main point of nitrox - longer NDLs. (for the same risk).

Of course, there is also IANTD's statement that "Oxygen is potentially twice as narcotic than Nitrogen. The upside being that at the partial pressures of oxygen within which we normally operate (0.21 to 1.6), oxygen narcosis is not a relevant issue. "

That is a separate issue but the fact remains on nitrox you wont get "less narc'd" as youre replacing nitrogen with something more narcotic (if the figure of 2x is true which im unsure then a PPO2 of 1.4 could be just as bad if not worse than air of the same mix. In any case, replacing one narcotic gas for another isnt going to reduce narcosis. (in any case, from 110ft onwards or so you start using leaner nitrox mixes so making them more similar to air the deeper you go...And the deeper you go the more narcosis is an issue).

Why did i do nitrox? Mainly because when abroad my NDLs would be longer or the rare cases i get to use it here, the deco stops are shorter so i get longer on my wreck and so on. If doing lots of multi days diving this can become a big boost. I didnt do it for extended safety margin or narcotic reduction (thats trimix which i definately cant afford).

 

[lamont]

The big difference is that you do metabolise O2, but not N2. I am getting a cert in EAN because at my age (54) using less nitogen at relatively shallow depths is easier on me than more n2. I will not dive - deeper, nor in most cases longer, but I will dive with less impact on my body (I hope).

At this point in the history of SCUBA, you can't say for certain what effects maximum NDL of nitrogen does to the body. You can't say there is no long term impact. You can't say, if you're over 50, add an extra 10 feet to your debth on the tables to compensate for your age. It just hasn't been studied that well.

So for me, the less small bubbles of n2 I have the better.

Stan

I feel much better doing a 1-1-1 ascent on a fairly aggressive profile on EAN32 than I do with a 1-1-1 on a completely weenie dive with 21%. If I'm diving air it seems like I need to do a 1-3-5 or so to feel good after the dive. Dissolved gas loading does not explain this at all, but I think that's a flaw in the dissolved gas model.

 

[Canadian_Diver]

Hey String,

I'm still waiting for you to send me a link to that DAN article about Nitrox not providing an additional layer of safety when used on standard tables.

By the way, I did check IANTD's website, they too list SAFETY/DCS as a reason for using Nitrox. IANTD FAQ

 

[DiveGolfSki]

That is a separate issue but the fact remains on nitrox you wont get "less narc'd" as youre replacing nitrogen with something more narcotic (if the figure of 2x is true which im unsure then a PPO2 of 1.4 could be just as bad if not worse than air of the same mix. In any case, replacing one narcotic gas for another isnt going to reduce narcosis. (in any case, from 110ft onwards or so you start using leaner nitrox mixes so making them more similar to air the deeper you go...And the deeper you go the more narcosis is an issue).

Let's use a hypthetical then, a dive to 110 fsw, one divers uses air and the other uses EAN 32.

Air Diver: PPO2 is at .91 and PPN is at 3.38
EAN36 Diver: PP02 is at 1.39 and PPN is at 2.77


Who has the better chance of getting narced? According to your point, they're both narcotic gases and the chances are even for both divers (the theory is oxygen and nitrogen may have roughly the same narcotic effect). So both divers will get narc'ed?

The theory of oxygen and nitrogen being equally narcotic is based on the fact that the O2 molecule is both dipolar in attraction and heavy. This would lead to the possibility that it "may" have anesthetic properties.

This would obviously only hold true for the gas that has not been metabolized. The last time I checked humans metabolize oxygen. Not the case with Nitrogen is it? It's inert and stays in your body. BTW, whats the benchmark PPN used for calculating trimixes nowadays? A PPN of 3.16, I believe?

So who has a higher risk of narcosis? (a) Air Diver; (b) EAN 36 or (c) both.

Let me think ..... Air diver has PPO2 of .91 and PPN of 3.38 ... Hmmmm, .91 oxygen is over 4 times normal ... assuming he's from Venus and can't metabolize oxygen. PPN 3.38 ... hmmmmm ... Whoa that's over the 3.16 threshold!!!!

Nitrox diver has PP02 of 1.4 .... hmmm not way over most accepted threshold ... again assuming he's a Venusian and can't metabolize oxygen. PPN is 2.77 is much lower than accepted thresholds.

What to choose???? String ... help!