More than "Advanced", but not really "Technical"

[Ontwreckdiver]

Have a look at the TDI Advanced Nitrox course. I know this is a over simplified explanation of the course but, it is basically a deco course with in recreational limits. It has been over 6 years since I took the course, but at that time you could do it with a single tank and a 40cf stage bottle.

Advanced Nitrox Diver | SDI | TDI | ERDI

 

[maniago]

That's not actually what it's doing.

When it first goes into deco it will require a 10 foot stop,but it's not aborting the dive.Just telling you how much deco is required at that time.
If you stay longer at depth the time required at 10 feet will gradually lengthen and eventually it will require the first stop to be at 20 feet. Stay longer and you will see a 30 foot stop and so on.

Doing significant deco on some (most??) recreational computers is not a good idea. My old Aeris computer indicates the length of time required at a particular stop. e.g after a long/deep dive it might say 3 minutes at 30 feet. What it does not tell me is that the total time to surface (30,20 and 10 foot stops) might be 40 minutes. In that situation I would have no idea how much deco I need to do,or if I have enough gas to do it ! Not a good situation.

The other problem is the algorithm may not be the best. When my Aeris is asking for the first stop at 30 feet my Shearwater probably wants the initial stop to be at 80 feet (Depends on depth/time obviously,but it's MUCH deeper. )

Well, ok it may not be what its trying to tell me, but when you're at say 100' and all of a sudden the alarms go off and the whole screen is blinking DECO 10', its a bit confusing as to what to do when you are used to NDLs and TimeToGo. When NDLs are drilled into your head, you get it. No drilling on Deco, no get it - probably when you need to get it the most too. Anyway, that's maybe more a philosophy training discussion, not this thread.

Yes, exactly wrt your Aeris computer - it doesn't tell me total time to the surface. And since I've now erred from my dive plan, I wouldn't understand how much is salvageable of the dive (because some at some depth probably is). Not a good situation (monday morning quarterbacks bite your tongue pls).

As they say, Forearmed is Forewarned, and I prefer to be as armed as possible.

 

[lowviz]

Well, ok it may not be what its trying to tell me, but when you're at say 100' and all of a sudden the alarms go off and the whole screen is blinking DECO 10', its a bit confusing as to what to do when you are used to NDLs and TimeToGo. When NDLs are drilled into your head, you get it. No drilling on Deco, no get it - probably when you need to get it the most too. Anyway, that's maybe more a philosophy training discussion, not this thread. ...//...

Very much this thread.

In addition, the idea is to dive more conservatively by factoring in various complications, plan your gas, and do any light deco as indicated. No biggie. Without the complications, (ie: age, temperature, stress, dehydration, etc) there would most likely be no deco obligation with a recreational gas load.

Beats bending over backwards to avoid crossing the dreaded NDL then just heading topside.

 

[victorzamora]

maniago, this is getting really OT so I started a new thread here about this.

Ontwreck diver, that would be a great class to take....but it's still much more technical than what I think is being sought out. It certifies you for pure O2. I wonder what else it "certifies" you for.

OP: one thing to consider about certifying as AN/DP to a "lesser degree" than someone hoping for 150ft, 3-gas dives is that you're still certifying the "techreational" diver to 150ft and 3 gases up to 100% O2. Even if your friend has no interest in doing this, the instructor issuing the card signs his/her name on the fact that he believes the student is ready to go to 150ft and dive 3 gases. That's why nobody should certify to "two different standards" in the same class. Doing so is unfair to all parties involved.

 

[boulderjohn]

It would seem, however, that if you weren't giving a course that actually taught deco procedures and planning of staged decompression, the best you could tell these divers would be "if you computer says you have a deco obligation, then just do what your computer says and don't ascend / surface until you have made it happy".

Ah yes, that is right, a ceiling. My bad. That said, "ceilings" are not taught or even talked about unless you have some kind of deco class or deco-buddy to talk to etc, so my neophyte mistake is probably good to illustrate that just a little more understanding of how deco works would make those of us "rec-ies" a whole lot more "aware" of what it means and how to be safe, yes?

This is now taught in beginning OW diving courses that teach computer usage. You are not taught to plan for deco, but you are taught to follow computer instructions in case you stray into it accidentally.

 

[doctormike]

Well, ok it may not be what its trying to tell me, but when you're at say 100' and all of a sudden the alarms go off and the whole screen is blinking DECO 10', its a bit confusing as to what to do when you are used to NDLs and TimeToGo. When NDLs are drilled into your head, you get it. No drilling on Deco, no get it - probably when you need to get it the most too. Anyway, that's maybe more a philosophy training discussion, not this thread.

Yes, exactly wrt your Aeris computer - it doesn't tell me total time to the surface. And since I've now erred from my dive plan, I wouldn't understand how much is salvageable of the dive (because some at some depth probably is). Not a good situation (monday morning quarterbacks bite your tongue pls).

As they say, Forearmed is Forewarned, and I prefer to be as armed as possible.

If you are talking about someone who is not trained in deco procedures, and who has a single source of gas which might or might not be enough for back gas deco depending on the obligation, then I don't understand what you think is "salvageable" about this dive, unless you are on a shallow shore reef where you can look at the fish while sitting just under your ceiling and offgassing...

Here's the situation that I think you are describing: You have blown past the NDL, and you didn't plan for this. So if you are not tech trained, then the "correct" answer is to ascend as quickly as you can to a bit below the ceiling that your computer is giving you (see victorzamora's other thread), so that you will off gas quickly, but minimize the risk of bubble formation that would happen if you inadvertently went above your ceiling.

TTS is useful for divers trained in deco procedures with planned gas switches, but I don't think that's what your computer is designed for. So if someone is planning deco, they should get the appropriate tools and training. And if they aren't, and don't have those tools and training, then they need to get to the surface as safely and efficiently as possible once they are past the NDL. That's what the computer is telling them, and they shouldn't be sitting at depth, loading nitrogen and trying to figure out a way of extending their dive...

 

[lowviz]

...//... It certifies you for pure O2. I wonder what else it "certifies" you for. ...//...

Oxygen. On the boat, in your car, at home.

...//... the instructor issuing the card signs his/her name on the fact that he believes the student is ready to go to 150ft and dive 3 gases. ...//...

Not exactly, it just says that you met course requirements. What you get from the course is what counts. The cert is just plastic, it isn't advanced EAN, it doesn't allow you to do anything special. Any good boat captain knows this. I have a full cave card that I wouldn't even think of using without a (good) cave instructor next to me. Been too long...

...//... That's why nobody should certify to "two different standards" in the same class. Doing so is unfair to all parties involved.

I agree that this could be an issue. Looks like PADI has found a fix for that...

 

[tursiops]

I've had students ask for the same thing....what do I do if my computer goes into deco? They have no desire to exceed 130 feet....in fact most are on Nitrox and stay above 100 feet. They are mostly good with gas consumption.

But a 100-foot dive on 32% gives them nominally 30 mins at depth....so running out of NDL is a sign of really poor situational awareness. However, it happens. PADI tells them to go to 15 feet and take an extended safety stop....8 mins or 15 mins, depending on how badly they exceeded their NDL. That, of course, is a "deco" stop.

But even more important than the 8 or 15 mins (or whatever your computer tells you to do at 10 feet) is having enough gas to do it. At 100 feet, a person with a 0.6 cuft/min SAC (pretty good) will use 2.4 cuft/min; that is 15% of their AL80 every 5 mins. So with 30 mins NDL they'll use 90% of their tank......which does NOT leave enough to get safely to the surface!

I think "reading the book" is insufficient training, especially if the book is just about your computer. Learning gas management is critical, and is more likely to save your life than worrying about DCS.

Tec 40 covers all this, in mostly recreational gear. Just 4 dives (the first is in confined water), pretty much recreational gear (although an H-valve or a 30cuft pony are needed) plus an SMB/reel. Dive #4 needs to get to 85 ft so many sites will not qualify. The class can also be taken in full tec gear, but that is not required. I also teach TDI, and there is no class that covers the same material.

---------- Post added January 6th, 2014 at 12:40 PM ----------

Have a look at the TDI Advanced Nitrox course. I know this is a over simplified explanation of the course but, it is basically a deco course with in recreational limits. It has been over 6 years since I took the course, but at that time you could do it with a single tank and a 40cf stage bottle.

Advanced Nitrox Diver | SDI | TDI | ERDI

There is no decompression discussed or permitted in the Adv Nitrox course. That is covered in the Decompression Procedures course, which is full-blown, not bare minimum deco.

 

[Lorenzoid]

Ah yes, that is right, a ceiling. My bad. That said, "ceilings" are not taught or even talked about unless you have some kind of deco class or deco-buddy to talk to etc, so my neophyte mistake is probably good to illustrate that just a little more understanding of how deco works would make those of us "rec-ies" a whole lot more "aware" of what it means and how to be safe, yes?

Thanks on the books.

The manual that came with my Suunto computer explained how to interpret the display should it ever indicate an obligatory deco stop, and what a "ceiling" is. It uses the terms "ceiling" and "floor" and appears to be written an in introductory manner for rec divers who are unfamiliar with these terms. Beyond that, I can't imagine any OW diver not having at least a rough grasp of how depth and time relate to ongassing and offgassing. With that basic concept in mind, the computer's introduction to ceilings and floors should make intuitive sense and provide everything one needs to know to handle the situation should it occur.

 

[boulderjohn]

PADI tells them to go to 15 feet and take an extended safety stop....8 mins or 15 mins, depending on how badly they exceeded their NDL. That, of course, is a "deco" stop.

That is only true if they are diving tables. If they take the computer version of the course, PADI teaches them to follow the instructions given by the computer.