Nitrox for shallow water artifact diving??

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Having given this some more thought, I think your purpose is to show that you have maintained all along that the NDLs for a 25 foot dive would be very, very long. No one has ever disagreed with that. In fact, I said that is likely the reason that there is not a 25 foot level on the PADI RDP--no one would dive that long, so it wasn't necessary.

The disagreement was that you said repeatedly that there is no tissue on-gassing at that depth, and there is no NDL at all. We were just trying to correct that misunderstanding.
  • There is tissue on-gassing at all depths until saturation levels are reached.
  • At 25 feet, it will take a long time to reach a tissue pressure that could result in DCS, but it can happen.
  • Shallower than 20 feet, if all tissues were to saturate at that pressure, the diver should be able to surface anyway.
 
“To estimate the risk of decompression sickness (DCS) for direct ascents from depth to the sea surface for personnel who are saturated with hyperbaric nitrogen, we analyzed 586 experimental air or nitrogen-based saturation dives. No DCS occurred on shallow saturation dives between 12.0 and 20.5 feet of seawater, gauge (fswg) but incidence of DCS rose abruptly when depth was deeper than 20.5 fswg, reaching 27% at 30 fswg. This is evidence of a threshold for clinical DCS.”
 
“To estimate the risk of decompression sickness (DCS) for direct ascents from depth to the sea surface for personnel who are saturated with hyperbaric nitrogen, we analyzed 586 experimental air or nitrogen-based saturation dives. No DCS occurred on shallow saturation dives between 12.0 and 20.5 feet of seawater, gauge (fswg) but incidence of DCS rose abruptly when depth was deeper than 20.5 fswg, reaching 27% at 30 fswg. This is evidence of a threshold for clinical DCS.”
Great quote! I wish that had appeared about 150 posts earlier.
 
I am quite sure that no recreational divers plan their dives (using either tables or computers),
I know of at least one non-technical diver who plans his dives, so you're wrong there.

Granted, those NDLs have long been coded into the brain, so there's rarely any reason to break out the hardcopy. But it's still planning, and it's still done using the tables.
 
I am quite sure that no recreational divers plan their dives (using either tables or computers),
I know of at least one non-technical diver who plans his dives, so you're wrong there.

Granted, those NDLs have long been coded into the brain, so there's rarely any reason to break out the hardcopy. But it's still planning, and it's still done using the tables.
I don't know why I did not respond to this part of the post when I responded to the whole thing earlier.

The word "plan" is a bit vague. In my experience on ScubaBoard, people who say that others do not plan dives really mean that those people are planning their dives differently than they plan theirs.

You don't need tables to plan the maximum depth and time of a recreational dive because a computer will do it more accurately. I bought my first computer nearly a quarter century ago. Before doing the second dive of a 2-tank dive, I always checked the planning mode to see if I had had enough surface interval to do the planned second dive. If not, I waited a bit longer before getting in the water. So when I eventually got in the water for my second dive, I knew what my maximum time would be if I stayed at the planned maximum depth. Of course, I rarely stayed at the planned maximum depth, so I would consult with the computer throughout the dive to see how the dive's reality compared with the plan. I would then ascend when the gas level reached a certain point.

Of, course, for some people that is not planning. Why not?

The post also mentioned cave diving as an example of dives that are properly planned. Really? In most cave dives, the divers determine a turning point (often following the rule of thirds) and then turn the dive and head back to the exit when one of the divers on the team reaches that gas pressure. How is that different from a recreational diver ascending to the surface upon reaching a certain gas pressure?
 
The word "plan" is a bit vague.

Very true. Dive planning for a typical "sight seeing" dive rarely needs more than two buddies agreeing on a turn-around event, often based on remaining air or approaching a NDL. Safe, adequate, and effective. A dive with an objective needs a much higher level of planning and add decompression to the mix and it gets even more detailed. I like to think in terms of "dive appropriate" planning.

I do everything from "follow my nose" recreational solo dives to practicing and choregraphing every move on a deep commercial dive.
 
I am quite sure that no recreational divers plan their dives (using either tables or computers)...

Hmmm. This is the only way I dive. Rec dives. Analog gauges and self-winding dive watch and tables. Tables for repetitive dives. (The magic numbers for non-repetitive dives were memorized decades ago.)

rx7diver
 
Unless you are diving in a hot tub, even warm water is less than 98.6 degrees of your normal body temperature. I wonder if the cooling of your body is some of the fatigue/lethargy you are experiencing. Have you taken your temperature before and after these dives? A long immersion in water lower than body temperature will drop your core temp.
 
You don't need tables to plan the maximum depth and time of a recreational dive because a computer will do it more accurately.
No, you don't need tables. But it helps a lot to know your NDL at some relevant depths. And those are most easily read from tables.

I have long memorized some NDLs (30m/20min, 25m/30min, 20m/45min, <18m/>1hr, ~50% longer on EAN32). From there on it's a question of whether it's a square profile or triangular/multilevel and doing an educated guess at how much longer my runtime will be in case of a triangular/multilevel profile. In any case, I'm obliged to give the DL/DO my max depth, max runtime and approximate direction, so "bimle around until the computer says I gotta surface" isn't an acceptable plan (or lack of such) in my world.

Club diving in Europe requires some form of planning, even for non-technical divers. We don't dive with a babysitter.
 
“To estimate the risk of decompression sickness (DCS) for direct ascents from depth to the sea surface for personnel who are saturated with hyperbaric nitrogen, we analyzed 586 experimental air or nitrogen-based saturation dives. No DCS occurred on shallow saturation dives between 12.0 and 20.5 feet of seawater, gauge (fswg) but incidence of DCS rose abruptly when depth was deeper than 20.5 fswg, reaching 27% at 30 fswg. This is evidence of a threshold for clinical DCS.”
I am so glad I missed the first 20+ pages of arguing semantics about what constitutes NDL and what is a dive plan.... did you guy cover split fins, too?

This makes sense when you think about it. DCS is bubble formation in tissue. If you don’t have a great enough pressure differential, bubbles will never form, No chance of DCS ever because gas will remain dissolved in tissue/blood and will simply cycle through.
 
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