Info Why are tables not taught in OW classes anymore?
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Are you sure? Here’s an explanation by DAN of a dive resulting in decompression sickness, without exceeding the computer’s algorithm.
The problem is that reliance upon dive computers has made a current population of divers dependent upon them, and not upon the knowledge of decompression limits, and why they were established in the first place. So today’s divers lack an understanding of the basics of why the no-decompression limits were set, and how some profiles, the computer deems safe, may not be. Divers of yesteryear would plan their dives before entering the water, go deeper first, then not tarry around a jigsaw dive profile. We also cautioned against diving to the “knife edge” of the no-decompression limits, as those limits were devised with the understanding that a certain percentage of Navy divers would get decompression sickness at the edge of the no-decompression limits.… Two decades ago the maximum allowable total dive time if a diver reached 30m depth would have been around 20 minutes if the dive was planned using tables, as it commonly was. This dive profile may even have been permitted using multilevel planning techniques. But today, modern dive computers do the work for us and such a profile is considered a “normal dive”.
The risk of decompression sickness is thought to be low among recreational divers because the majority of dives come nowhere near the no-decompression limits. After two previous days of repetitive diving, this diver suffered an injury which was diagnosed as a serious case of decompression sickness, probably without violating the dive computer’s limits. That the diver made a safety stop was prudent, but of particular note is that there was oxygen onboard the boat, and the diver continued breathing oxygen on the way to the ER.
After multiple hyperbaric treatments the diver is 99 percent recovered, which is good news, though it should be pointed out that bilateral symptoms affecting all four limbs are not typical of decompression sickness.
Regardless, this case serves as a reminder that our dive computer may well keep recalculating our allowable limits but that does not mean we should dive to those limits. If 100,000 divers dive to the limits then, even though they did not “break the rules”, by probability alone some will get the bends.
Peter Buzzacott, MPH, Ph.D.
“Normal” Dive Resulted in Decompression Sickness
This case serves as a reminder that our dive computer may well keep recalculating our allowable limits but that does not mean we should dive to those limits.dan.org
SeaRat
If my memory is correct, we were out of the water on the third dive at about 4:00 PM. That would give a 2-hour surface interval for the fourth dive.I'll let the altitude stuff go, and you can calculate the dive using #145, 146 and 147.. For the calculations, use 1/2 hour surface interval between each dive.
SeaRat
If my memory is correct, we were out of the water on the third dive at about 4:00 PM. We were in a 7-man life raft, and simply paddled to different sites for these dives. That would give a 2-hour surface interval for the fourth dive.Recap:
145: 90' 25 minutes
30 minute SI
146: 40' 35 minutes
30 minute SI
147: 40' 30 minutes
What time did you surface on dive 147? Are we supposed to assume 5:30pm?
BTW, you should check the "Total" column on dive 146 (and therefore 147)
It's kind of cool to be discussing 50 year old dives. Maybe I should reconsider about not logging my dives.
SeaRat
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I can see no downside ......and only upside........from learning and understanding tables.
Yes, I’m sure there’s no need for abacuses and slide rules.
And give me a break about one instance from DAN that falls into your narrative. I can you 100 examples of people doing tables wrong and putting themselves at risk.
There is no need for calculator if I need to do simple calculation.
I am pretty sure we all made mistakes in life but not able to understand one's own/rental DC is unacceptable and I have seen it far too many times.
Plenty of divers have no idea why certain figure in his/her DC fluctuate all the time and also the meaning of arrow/alarm etc etc.
Computer/Table does not get bent but diver does.
Human is not infallible.
Oh, there’s more than one. Here’s an example:
Ultrasound in the diagnosis of acute-phase decompression sickness
A 53-year-old man, who performed a 44-minute dive to a depth of 21 meters, felt severe abdominal pain with dyspnea after surfacing. An ultrasound stud…
www.sciencedirect.com
In 2010 DAN published an article titled “The Validation of Dive Computer Decompression Safety,” in which they stated:
But on the other side, you’d think that the incidence of decompression sickness would decrease with dive computer usage; it hasn’t. Apparently, unless something has happened since 2010, there is no standard for validation of dive computer algorithms. Please read this article, and the expert commentary toward the end of the article.
The Validation of Dive Computer Decompression Safety
There is a lack of hard data on the validation of decompression safety and the intersection of dive computers. Read more.
dan.org
SeaRat
You understand how flawed your Mickey Mouse logic is right? Lol. Bad instruction can take place in a computer class or tables class. The difference is that the fundamentals of computer diving (any computer) can be mastered in 5 minutes of quality instruction. The same is NOT possible with tables. All things equal, ask a brand new diver which is easier, safer, quicker, and more reliable; their brain and their understanding of tables or the dive computer. The answer will shut this argument down. You know it. I know it. The newer divers reading this thread know it.
For what its worth LA county still teaches tables. But they are far from mainstream.
I personally think they are useful so much in that they help a new diver understand what is going on, at an abstracted level of their computer. Teach them tables, then show them the magic and joy that is a dive computer. Avoid the dive computer being the magic box, but also be realistic that it will be what they dive with the majority of the time (and likely will be safer).
I personally think they are useful so much in that they help a new diver understand what is going on, at an abstracted level of their computer. Teach them tables, then show them the magic and joy that is a dive computer. Avoid the dive computer being the magic box, but also be realistic that it will be what they dive with the majority of the time (and likely will be safer).
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