Is the Deep cert really necessary?

[Racer_X]

I was certified in 1986. At that time, the NAUI limit was 120 feet for recreational diving. In discussions, it was clearly stated that the reason for this is the fact that deco diving wasn't considered recreational. Training emphasized dive planning within NDL limits only. IIRC, 1986 pre-dated Nitrox and Tri-mix diving, although perhaps they were used in commercial diving - which would also differentiate the diving types. i.e. Recreational = diving for fun vs commercial = diving for money (vs military = diving for money because you have to or you'll be shot).

So for those in search of a definitive why, I think you'll be disappointed.

 

[SwimAway]

Did the OP ever come back?

Anyway, if the question is, "Do I need it to go on a paid dive trip?":
Based on my experience you should always find out from the dive operator what they will require for a given dive before spending money and traveling, they are all different.

Also I think the PADI Advanced and/or specialty dives can be done "in the field" with a lot of dive operators, so worst case you could work out some deal where you get your deep dive cert. on the same trip as the trip that requires it. Again, that would be something to find out directly from them as every operator is very different as to what they are set up to do.

 

[Lorenzoid]

Did the OP ever come back?

Anyway, if the question is, "Do I need it to go on a paid dive trip?":
Based on my experience you should always find out from the dive operator what they will require for a given dive before spending money and traveling, they are all different.

Also I think the PADI Advanced and/or specialty dives can be done "in the field" with a lot of dive operators, so worst case you could work out some deal where you get your deep dive cert. on the same trip as the trip that requires it. Again, that would be something to find out directly from them as every operator is very different as to what they are set up to do.

Thanks for the reminder of what the OP was apparently concerned about. I think some of the
early replies indicated that dive ops more often ask to see an AOW card and/or evidence of having done a recent "deep" dive than they ask to see a Deep card. But the related question of how useful is the Deep course is perhaps the more interesting question--at least it was to me.

 

[tursiops]

You are so sure of yourself on something that is most likely quite wrong. Why don't you stop the silly guessing games and just say what you think the "answer" is?
The 130 ft/40m recreational limit is older than PADI, older than Nitrox and O2 toxicity concerns, and -- as has been stated in various forms in this thread -- is based primarily on gas usage, narcosis, and avoiding deco with useful bottom times.

In addition, if you read the material from those who put the NOAA Nitrox concepts together, EAN32 was specifically chosen so that its MOD (for PPO2=1.6) of 40m matched the already traditional no deco recreational limit of 40m (=130 ft in round numbers). That no deco limit was based on useful bottom times with air, avoiding narcosis, and the amount of air in the popular (at the time) 72 cuft tanks.

 

[cousindna]

In addition, if you read the material from those who put the NOAA Nitrox concepts together, EAN32 was specifically chosen so that its MOD (for PPO2=1.6) of 40m matched the already traditional no deco recreational limit of 40m (=130 ft in round numbers). That no deco limit was based on useful bottom times with air, avoiding narcosis, and the amount of air in the popular (at the time) 72 cuft tanks.

OK. You were all wrong and not even close.

When you give an individual oxygen at the surface they have a PPO2 of 1.0 and a PPO2 of 1.6 is the generally accepted maximum during the rest portion of a Tec dive and 1.4 if you are in the energetic portion of the dive.

So, if 1.6 PPO2 is considered the max. then the deepest you can breathe 100% O2 is 6 metres. (?2)

As for ?1, if humans can safely breathe 100% O2 at the surface then they can safely dive to a depth at which their PPO2 will be 1.0, OR as PADI says, 40 metres at which point you must jump through hoops if you exceed this value.

And yet none of you mentioned that every dive you do, 10,20,30 m3tres, is a "decompression" dive and that if you follow PADI guidelines you can directly return to the surface without concern for DCS OR if you exceed 30 metres but NOT 40 metres, you simply insert a "safety stop" to assist in the "off gassing" process

If you are using nitrox, even 22%, max depth is less than 40 metres.

Once you cross the Rubicon of 40 metres then you are committed to additional decompression time/depth and neither prevent you from diving to 50, 60, 70 metres - PPO2 at 70 is 1.6. What prevents you doing these depths should be your lack of professional training and education that comes with Deep Diver Specialty, TecRec 40, 45 and 50 and TRIMIX 65 and, a tonne of in kind dives.

Best regards

Dave

 

[steinbil]

OK. You were all wrong and not even close.

Haha. You're funny.

If you are using nitrox, even 22%, max depth is less than 40 metres.

Primarily because of gas density. Second, because of gas narcosis. Lastly, for practical reasons concerning gas management, gear, NDLs etc.

 

[tursiops]

OK. You were all wrong and not even close.

When you give an individual oxygen at the surface they have a PPO2 of 1.0 and a PPO2 of 1.6 is the generally accepted maximum during the rest portion of a Tec dive and 1.4 if you are in the energetic portion of the dive.

So, if 1.6 PPO2 is considered the max. then the deepest you can breathe 100% O2 is 6 metres. (?2)

As for ?1, if humans can safely breathe 100% O2 at the surface then they can safely dive to a depth at which their PPO2 will be 1.0, OR as PADI says, 40 metres at which point you must jump through hoops if you exceed this value.

And yet none of you mentioned that every dive you do, 10,20,30 m3tres, is a "decompression" dive and that if you follow PADI guidelines you can directly return to the surface without concern for DCS OR if you exceed 30 metres but NOT 40 metres, you simply insert a "safety stop" to assist in the "off gassing" process

If you are using nitrox, even 22%, max depth is less than 40 metres.

Once you cross the Rubicon of 40 metres then you are committed to additional decompression time/depth and neither prevent you from diving to 50, 60, 70 metres - PPO2 at 70 is 1.6. What prevents you doing these depths should be your lack of professional training and education that comes with Deep Diver Specialty, TecRec 40, 45 and 50 and TRIMIX 65 and, a tonne of in kind dives.

Best regards

Dave

Nah. Mostly nonsense. You are confused by the coincidence of some numbers, and are taking much too seriously what PPO2=1.6 means. There are plenty of dives using air to 40m (and beyond) to make your hypothesis invalid that PPO2=1 is some magic number.
Your very first sentence is evidence that you are confused: "if humans can safely breathe 100% O2 at the surface" is incorrect. We can't breath pure O2 at the surface for an extended period...we have to take air breaks. Do a little homework and check your facts.

 

[inquis]

if 1.6 PPO2 is considered the max

That wasn't the case when the 40m line was drawn. Consensus about max PO2 has changed since then, but for some reason the 40m hasn't.

 

[waxrash]

I would say yes, but lots of follow up questions beginning with where are you diving? As a 20+ year instructor I tell students that they should take a specialty course for every new experience. I certainly know they can do it without my class, but will they have fun? Confidence = fun. Diving in the open Atlantic, off the coast of NC is challenging for inexperienced divers. It is up to me to drive the value in the course so that they come away more confident in the environment. Obviously covering the agencies training program first but then simple stuff like having the unlock a combination lock at 20 ft then at 120 ft, noting the delay under nitrogen loading and stress, having them record air consumption at various depths to understand that air consumption goes up with depth. To tech oriented divers this may sound like child’s play, I get that. However, I focus on building confidence in recreational divers with simple and practical exercises under supervision.

Most dive operations that I have used off the coast of NC require advanced open water cert including deep and wreck specialties because most of our sites are wrecks and deep.
You are most likely not going to see the bottom from the surface, nor the surface from the bottom and it freaks some people out who have only done tropical 60’ dives. To go visit U352, most students will kill their tank with only 5 minutes of bottom time due to stress and depth. Don’t you want those first couple of dives with a competent dive leader or instructor?

I have never had a student take a specialty course from me that said it was a waste of time or money and I know I’m not that good. I think it’s because they left more confident.

 

[Alekseolsen]

As a 20+ year instructor I tell students that they should take a specialty course for every new experience.

I hope by this you mean something VERY different than I think of as " a new experience". Frankly I want every dive to be "a new experiece" if you mean every new 20 meters of depth I could follow that, but a course for boat, dark, Night, cold, with fish, without fish, blue water accent, beach accent etc. Would just kill all joy that've "lured me" into this sport. A course is something I need to do in order to safely do a type of dives I wish to do (and at some sites, to be allowed to do them), but they have never been a target in themselves.