Advanced open water?

[jj1987]

being that all agency’s limit Open Water Divers to a Max depth of 60ft NDL and AWO to a max depth of 130ft NDL.

Being that an instructor certifying an OW Diver to Cavern is violating OW Certification Standards that instructor will be Liable if that person ever has an accident at least until another instructor violates standards and gives them a higher certification!

As a Cavern Instructor I will/would never accept an OW Diver into Cavern Training, not to mention that it violates the standards NAUI Cavern Diver Course.

Cavern Diving
The cavern diving course is taught in a minimum of two days and includes classroom lectures, field exercises, open water line drills and a minimum of four cavern dives. This course emphasizes planning, procedures, environment, propulsion techniques, buoyancy skills, problem solving, equipment modification and the focuses on the specialized needs of the cavern diver.

Purpose: To teach the safe exploration of the cavern environment within specified limits. The course develops and establishes minimum skills, knowledge, dive planning abilities, problem solving procedures and the basic abilities to safely cavern dive.

Prerequisites: Advanced open water or equivalent or 15 logged non training open water dives with open water certification.

Wouldn't the cavern cert override the OW in this case, similar to taking a OW cert diver to 80ft deep during their AOW course? IIRC the NACD suggests a max depth of either 100 or 130ft after taking the cavern course.

It doesn't say that anywhere in my SSI OW manual.

Not sure what exactly they recommend, but in their nitrox course that I'm currently taking, they seem to rely more on a calculated ppo2 than picking a random magic number like 60ft. A quick google search made it seem like the magic number is 18 meters.

[SuPrBuGmAn]

NACD cavern has a max depth of 100', TDI will allow 130', but suggests staying shallower than 100'.

My SSI OW booklet suggests staying shallower than 100', but doesn't stipulate a max depth aside from staying within NDL recreational limits(130' on air). LOL.

[jj1987]

NACD cavern has a max depth of 100', TDI will allow 130', but suggests staying shallower than 100'.

My SSI OW booklet suggests staying shallower than 100', but doesn't stipulate a max depth aside from staying within NDL recreational limits(130' on air). LOL.

That seems a lot more reasonable than saying 60ft limit in my opinion and from my observation....I've yet to hear what dangers are present at 80ft that are not present at 60ft. I still kind of find it funny that 130ft is the safe recreational limit on air (ppo2 of 1.037), and their safe limit on ean36 is 94ft (ppo2 of 1.39). I'll admit to being a n00b with this stuff, but it seems random to say the least. Overhead training limits make sense to me, but OW have always left me wondering "why". If an instructor could fill us in, I'd be interested to hear the explanation.

[SuPrBuGmAn]

You have to take more into account than ppO levels, the narcotic effect of air is generally accepted as being much worse in the 100+' range.

Narc'd and in an overhead... :/

[jj1987]

the narcotic effect of air is generally accepted as being much worse in the 100+' range.

Is there a known reason why, or is this something divers have observed and an explanation hasn't been found yet?

[jimmy herbert]

Is there a known reason why, or is this something divers have observed and an explanation hasn't been found yet?

They'll cover that in your AOW class.

[SuPrBuGmAn]

They shoulda covered that in your OW class :/

[jj1987]

They shoulda covered that in your OW class :/

In our OW class we discussed that oxygen tox, and were told that dives below 100ft had an increased risk to the central nervous system, causing convulsions and other things of that nature. I don't think we went into what caused this, but were given the guidelines and told to obey them. Maybe I was a bad student, or maybe it wasn't covered, but I was under the impression that your body absorbed an exponentially greater amount of oxygen as more pressure builds up, but I never fully understood why.

Were you saying that the ppo2 formula is incorrect after a certain depth and the danger becomes higher, or that the effects of being narced increase with depth due to other factors like lack of light, color shifts as certain wavelengths dissapear, more pressure on your body, etc (I know these types of things can increase the effects of alcohol and drugs)?

The reason I'm wondering here, is that the ssi nitrox class I'm currently in doesn't seem to enforce depth limits as much as it says to just watch out for your ppo2, and keep it under a 1.4. Let's say you're diving air at 100ft, your ppo2 is .85, and a 36% nitrox blend is higher than that at 57ft with a ppo2 of .98, yet you're well within the "safe" limit, as you're still under 1.1 (or 1.4). I'm sorry if I'm being ignorant here, it just seems there's an external factor I'm not considering.

[Mike Edmonston]

In our OW class we discussed that oxygen tox, and were told that dives below 100ft had an increased risk to the central nervous system, causing convulsions and other things of that nature. I don't think we went into what caused this, but were given the guidelines and told to obey them. Maybe I was a bad student, or maybe it wasn't covered, but I was under the impression that your body absorbed an exponentially greater amount of oxygen as more pressure builds up, but I never fully understood why.

Were you saying that the ppo2 formula is incorrect after a certain depth and the danger becomes higher, or that the effects of being narced increase with depth due to other factors like lack of light, color shifts as certain wavelengths dissapear, more pressure on your body, etc (I know these types of things can increase the effects of alcohol and drugs)?

The reason I'm wondering here, is that the ssi nitrox class I'm currently in doesn't seem to enforce depth limits as much as it says to just watch out for your ppo2, and keep it under a 1.4. Let's say you're diving air at 100ft, your ppo2 is .85, and a 36% nitrox blend is higher than that at 57ft with a ppo2 of .98, yet you're well within the "safe" limit, as you're still under 1.1 (or 1.4). I'm sorry if I'm being ignorant here, it just seems there's an external factor I'm not considering.

O2 is not the only determinating factor. You have to include the PP of nitrogen and the affect it has on you. This should have been covered in your basic OW class. Although, the answers you seek are only a good Nitrox class away. Also, when I teach an AOW class, I explain the effects of Nitrogen at depth, and the reasons behind our "diving depth limits" for OW divers following NDL's.

I applaud your enthusiasm, but please don't try bypass classes by reading threads. There's a big difference between the internet and real life.

Safe Diving

[jj1987]

O2 is not the only determinating factor. You have to include the PP of nitrogen and the affect it has on you. This should have been covered in your basic OW class. Although, the answers you seek are only a good Nitrox class away. Also, when I teach an AOW class, I explain the effects of Nitrogen at depth, and the reasons behind our "diving depth limits" for OW divers following NDL's.

I applaud your enthusiasm, but please don't try bypass classes by reading threads. There's a big difference between the internet and real life.

Safe Diving

Understood, thanks for your response.

Unfortunately I can't blame this one on my OW instructor but rather me having a brain fart, after you mentioned that I recall him going over daltons law and how it relates to partial pressures, plus chem class covered this on the first week as well. I had let nitrogen completely slip my mind here while posting, since so much of the focus on the nitrox class was oxygen. I'm guessing since oxygen tox is the more pressing issue on nitrox, that's why it's mentioned more, I guess that was a stupid question I could have avoided asking with a bit more thinking. I've been reading way too many nitrox discussions the past few days that I think I caught myself fumbling ox tox and nitrogen narcosis as one in the same. I guess that's the downside of the springs being flooded and having way too much internet time.

Give me one second and I'll review my notes and answer this question for myself (and for anyone else who might stumble across the thread).

OK heres the edit....I didn't see any problems we had to work out from my OW notes, but I still have my notebook from college chem, which had notes on this, and the formula was in my OW notes, so putting the two together I think I've explained my own question.
ppn2=[(d+33)/33]*.79
ppn2= partial pressure of nitrogen
d= depth in salt water ft
We add 33 to include the 1atm of surface pressure
We multiply by .79 for the nitrogen content in the air.

So the rec limit for ppn2 is around 3 (I googled it, it appears some agency's are higher than others, but all around 3).
3=[(d+33)/33]*.79
3.797=(d+33)/33
125.316=d+33
d=92.316

So around 92ft we start to come into the >3 range of ppn2. 36% nitrox would have a ppn2 of around 2.44, so ox tox would come into play before nitrogen issues would. Hopefully I'm right this time. This is why I hate giving people round numbers to memorize, it's so easy to have a brain fart and forget what they mean...