IANTD EAN vs PADI EAN courses

[tursiops]

From my CCR training, it was pounded into me to "Always know your PO2!" At any time in the dive I needed to know what it was (within a reasonable amount). That is intended to ensure that I am always within range of my target PO2 (1.2 during the dive 1.6 if possible during deco).

Knowing your cumulative exposure (oxygen toxicity units) is also important, and takes into account both PO2 and time.

My earlier comment was that it sounds like the OP is muddling the two together.

I'm sure you mean PPO2, not PO2. Right?

 

[wedivebc]

So it's not "all about PO2" right? As I said earlier, there are 2 kinds of O2 exposure to be concerned about.

Next time read before deciding to be a condescending prick.

I am sorry if I somehow offended you. It was not my intention to come off as a condescending prick.

Peace.

 

[Remy B.]

Looking at the DAN comments of Oxigen Toxicity, they just mention EAN but they don't mention what % of EAN, I can undesrtand breathing a high EAN % mix and passing the depth limit, then there is the time off exposure that with a single tank and staying inside your NDL are kind of not so easy to reach, taken that a normal dive where you are moving very slowly and hardly doing any efford, just looking at fish and coral.

the DAN as well as other information mention about work part during diving, but is recreational diving not about relaxing and going slow enjoying the view ??

During the Nitrox course will they mention work/efford and PPO relation???

 

[tomfcrist]

We'll rec diving is nice when it's just cruising effortlessly, but more often than not where I dive there will be a current, which can turn an easy dive into a lot of work....real quick like.

You will learn( or should learn) about CNS O2 toxicity( short exposure to high ppO2) as well as pulmonary O2 toxicity( which will be completely irrelevant to you). Take the class, listen to the lectures and if your instructor can't answer your questions, we will still be here to help.

 

[Remy B.]

Thanks Tom.

when sudden current show up, is it not time to go up to shallower water or call the day or both? Taken in account I'm talking about shore diving not boat diving, I guess it will not be nice to be in a heavy current while on boat diving

 

[Colliam7]

Looking at the DAN comments of Oxigen Toxicity, they just mention EAN but they don't mention what % of EAN,

That is because the absolute percentage of oxygen in the mix is essentially irrelevant to a consideration of oxygen toxicity. What is most relevant is the partial pressure of oxygen. And, that is what is (repeatedly) emphasized in the DAN article (and most enriched air training courses, irrespective of agency).

I can undesrtand breathing a high EAN % mix and passing the depth limit,

Good, although I would note that you don't have to have a 'high EAN% mix' to exceed the PPO2 threshold. Breathing a 28% mix at 179 feet is essentially the same as breathing a 40% mix at 115 feet - both are associated with a PPO2 of ~1.8, not a good situation to be in.

then there is the time off exposure that with a single tank and staying inside your NDL are kind of not so easy to reach, taken that a normal dive where you are moving very slowly and hardly doing any efford, just looking at fish and coral.

You appear to be thinking more along the lines of the overall 'area under the oxygen concentration - time curve'. While that is not without importance, particularly with regard to pulmonary oxygen toxicity, the best available data suggest that the more critical / dangerous (neurological) manifestations of oxygen toxicity are associated with the partial pressure of oxygen. In reality, in recreational diving. oxygen toxicity is uncommon, so the data are somewhat sparse, and hard and fast conclusions about statistical correlations between PPO2 and toxicity are challenging to develop.

the DAN as well as other information mention about work part during diving, but is recreational diving not about relaxing and going slow enjoying the view ??

In principle, yes. But, don't misinterpret the term 'working' - it really refers to any time you are doing something OTHER THAN hanging / hovering almost motionless at a safety stop, or a decompression stop. So, even if you are just swimming slowly along, just looking at fish and coral, and enjoying the view, that is part of the 'working' portion of the dive.

Now, going back to your original post, I will add a comment that may cause concern to some. Just because you slightly exceed a PPO2 of 1.4 you will not necessarily manifest oxygen toxicity. A small percentage of divers may, most won't. Just because you slightly exceed a PPO2 of 1.6 you will not necessarily manifest oxygen toxicity. A small percentage of divers may, and that percentage is probably somewhat higher than those who slightly exceed 1.4, but most won't. As the PPO2 exposure - independent of the duration of exposure - increases, the probability of manifesting neurological signs of oxygen toxicity grows. For that matter, just because you slightly exceed a PPO2 of 2.0 you will not necessarily manifest oxygen toxicity. The problem is, most of us don't know where - at what partial pressure - we will have an issue. I certainly don't. And, while I wouldn't necessarily be all that bothered by 'visual disturbances' (the 'V' in VENTIDS), or by 'Irritability' (the 'I' in VENTIDS), the 'S' in VENTIDS probably would ruin my day. And, the signs /symptoms do not necessarily present in a crescendo fashion - the 'S' may be the first manifestation. So, I think I will just go along with the prevailing wisdom, even if the data are a bit sparse, and stay at or below 1.4.

During the Nitrox course will they mention work/efford and PPO relation???

Yes, they certainly should! For conditions of substantially increased effort - e.g. swimming against a moderate current - you will probably hear recommendations that you should be even more conservative, and stay below a partial pressure of oxygen of 1.2, possibly even 1.0.

It can mean that. But in NC it just means it's time to "suck it up buttercup".

Well said! If you spend 2 - 2.5 hours on the boat to get to a wreck site (not to mention the 3-5 hours drive just to get to the coast), and you have been blown out before even leaving the dock the two (or 3, or 4) times that you tried before to get to the site, you are probably going to put up with some current, even if it means imitating a flag on a pole at times.

 

[tomfcrist]

Thanks Tom.

when sudden current show up, is it not time to go up to shallower water or call the day or both? Taken in account I'm talking about shore diving not boat diving, I guess it will not be nice to be in a heavy current while on boat diving

It can mean that. But in NC it just means it's time to "suck it up buttercup".

 

[hroark2112]

Well said! If you spend 2 - 2.5 hours on the boat to get to a wreck site (not to mention the 3-5 hours drive just to get to the coast), and you have been blown out before even leaving the dock the two (or 3, or 4) times that you tried before to get to the site, you are probably going to put up with some current, even if it means imitating a flag on a pole at times.

I've definitely been blown out more times than I care to think about! My first dive on the U352 I only saw the stern of the wreck before I was nearly OOA. It was that hardest safety stop I've ever had to do, my hands were hurting trying to hang on to the bar!