PADI's dive depth standards - Vague?

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Scuba diver is now half an open water course requiring 2 OW dives, limits you to 12m or depth with a divemaster or higher. Glorified try dive

 

[Karibelle]

So... you're saying narcosis does not begin until 130 feet?

While I'm sure narcosis avoidance played a factor in wanting to set a depth limit of some sort, the 130' rule was indeed adopted from Navy standards... not a number at which narcosis is suddenly a concern.

No, I'm not saying that narcosis has no effects above 130', nor am I saying (or thinking) that narcosis is "suddenly a concern" at that depth, and no concern above that depth. I am simply showing that an excerpt from the Encyclopedia of Recreational Diving indicates that the effects of narcosis below 130' are a determining factor in setting that "limit."

As an aside, I find it curious that folks here tell me to "look at xxxx with an open mind" (not you, specifically, CompuDude) and then seem to believe that the factoid that they've grabbed onto is the truth, the whole truth, and nothing but the truth.

kari

 

[Walter]

Kari,

You are correct about narcosis. Its effects are actually measurable as shallow as 30 feet. Narcosis is one of the reasons some agencies keep their recommended depth limit at 130 feet and why others have their recommended depth limit at 100 feet. Narcosis was not the reason the 130 feet limit was originally set. It was originally borrowed from the US Navy.

While I know a little about the early days of diving, Thalassamania is someone I consider an expert and Sam Miller makes us both look like beginners.

As for keeping an open mind, I believe I was the one who encouraged you to do so. Have I grabbed onto a factoid and held it with a closed mind on this topic? If so, I apologize and humbly ask you show me where so I may reexamine it with a different attitude.

 

[Karibelle]

Kari,

You are correct about narcosis. Its effects are actually measurable as shallow as 30 feet. Narcosis is one of the reasons some agencies keep their recommended depth limit at 130 feet and why others have their recommended depth limit at 100 feet. Narcosis was not the reason the 130 feet limit was originally set. It was originally borrowed from the US Navy.

While I know a little about the early days of diving, Thalassamania is someone I consider an expert and Sam Miller makes us both look like beginners.

As for keeping an open mind, I believe I was the one who encouraged you to do so. Have I grabbed onto a factoid and held it with a closed mind on this topic? If so, I apologize and humbly ask you show me where so I may reexamine it with a different attitude.

Hi Walter,

Yes, you are the one who encouraged me to keep an open mind - and I hope that I am, and can continue to do so. You are not who I had in mind when I made my comment above. I do find that some of the "oldtimers" here do tend to respond to newbies like myself with a "No." answer and attitude, rather than with the Mentor Mentality that I would prefer. I respect the depths of experience that some of you have in comparison to myself, but submit to all of the experts that just because we're new doesn't mean we're stupid, and sometimes when we put forth a differing viewpoint, it would be more helpful to share your experience rather than just telling us "No."

As I tell my students, Todo al mundo es principiante alguna vez.

kari

 

[rawls]

No, while that's convenient, the 130 limit comes from the depth at which the US Navy made an operational shift from scuba to surface supplied air. ppO2 never entered the discussion.

Thal...Thanks. Question for clarification...Is it "possible" for a diver to experience an O2 hit at 132'? I want to make sure whether or not I am correct in saying this much...Still learning

With my own copyright apologies, this is from the Encyclopedia of Recreational Diving:

"The problem with narcosis, then, isn’t the
narcosis, but the impairment it can cause by
delaying responses to problems, affecting
decisions related to safety and interfering
with motor skills. It is narcosis (along with
extremely short no stop limits) that puts the
recreational depth limit for air/enriched air
diving at 40 metres/130 feet."

So, I say "no" to your "no."

karibelle...
You are absolutely correct in what the ERD says, however it states earlier in the topic that "Although there's individual suseptibility and personal variation, in the effects typically become, noticeable at approximately 30 meters/100 feet. At this depth, narcosis is typically subtle with slowed thinking, increased problem solving times and, in some divers, a mild sense of euphoria or well being."

I think what the book may have been alluding to is the degree of potential impairment. That at 130 ft the effects will be more noticeable. Not sure I am interpreting it correctly however. What they have written does seem to be very confusing/misleading.
Will appreciate anyone chiming in for interpretation...

 

[Thalassamania]

Thal...Thanks. Question for clarification...Is it "possible" for a diver to experience an O2 hit at 132'?

132 feet is 5 ata with a ppO₂of 1.05, oxtox is rather unlikely, I've never heard of it at that level, but I guess it's possible.

 

[rawls]

Thal...forgive me for just putting Thal, but I keep screwing up the spelling Thanks for all the info you have provided for clarification...preciate it....

 

[Walter]

Hi Walter,

Yes, you are the one who encouraged me to keep an open mind - and I hope that I am, and can continue to do so. You are not who I had in mind when I made my comment above. I do find that some of the "oldtimers" here do tend to respond to newbies like myself with a "No." answer and attitude, rather than with the Mentor Mentality that I would prefer. I respect the depths of experience that some of you have in comparison to myself, but submit to all of the experts that just because we're new doesn't mean we're stupid, and sometimes when we put forth a differing viewpoint, it would be more helpful to share your experience rather than just telling us "No."

As I tell my students, Todo al mundo es principiante alguna vez.

kari

Darlin', my Spanish is a little rusty. All of the world is .......?

While I've never met you and our contacts have been limited, I've already seen enough that you have earned my respect and I strongly suspect you'll earn more as time goes by. You are new to diving as we all were at one time, but you have a spark not found in all folks new or experienced. You are sharp, you're willing to look at different angles and you even made me see a new wrinkle on PADI's order of presentation. For that, I sincerely thank you. I still strongly disagree with that order of presentation, but you've given me a new insight that I believe will be beneficial in my future. I hope as time goes on we become friends and eventually get the opportunity to share a dive. I expect goods things from you.

 

[rawls]

Walter,

I got alot of appreciation from what you just wrote...

 

[letterboy]

Todo al mundo es principiante alguna vez.

Everything to the world is nascent sometimes.

nas·cent /ˈnæsənt, ˈneɪsənt/ Pronunciation Key - Show Spelled Pronunciation[nas-uhnt, ney-suhnt] Pronunciation Key - Show IPA Pronunciation
–adjective
1. beginning to exist or develop: the nascent republic.
2. Chemistry. (of an element) in the nascent state.