Another question about no-fly times

[Thalassamania]

Thal it isn't always background so no need to talk down to people here. Using these guidelines are inteligent and knowing them is being informed. Not knowing these guidelines at all is not being informed and the OP is making himself informed by asking. The vast majority are very happy with the guidelines and following them not because of lack of background but because the guidelines are simple and straight forward. Like with anything if you want to learn more there is more indepth information that can be had by researching decompressio theory.

I'm not "talking down" to anyone, simply stating facts. Divers have two choices, to use recommendations that are, at best, based on some situation that is likely more extreme than the actual situation at hand, or to educate themselves to be able to base their decisions on what they understand to be the actual circumstances with whatever level of added conservatism they feel is appropriate. I recommend the latter path, that's all, its really not that complex.

 

[endurodog]

Thal when you state things like you did it comes as talking down, maybe you didn't mean it that way and maybe that communication style is what leads to conflicts on the the board. But aside from that. No one has said it was complex at all but you. The simple guidelines put out by PADI and DAN while maybe not as exact as figuring it the way you suggest, work very well for the majority and that is while they are recommended by the leading certifying agency in the world and the leader in recomendations for dive safety.

 

[Thalassamania]

... recommended by the leading certifying agency in the world and the leader in recomendations for dive safety.

That's called an "appeal to authority," a classic logical fallacy, and let's not forget how accurate they were, and what the reasons were, when both organizations tried to vilify NITROX, "the devil gas."

 

[boulderjohn]

If the above is the new standard, is there anything about multiple dives? are considering all the previous dives a person has done?

Everything depends upon what you mean by "new." The newest copyright date on my copy of the PADI tables, which include those rules, is 1994. I got those tables when I was certified, which as not long after that. DAN's workshop that formalized the present guidelines was conducted in 2002. The NOAA ascent to altitude tables don't have a date on them, but they have been around for a very long time. They are not the same as the DAN guidelies, but they offer a range of anywhere from 0-24 hours before flying depending upon your exposure.

 

[endurodog]

I can't think of an org in the world that hasn't changed an opinion on anything. Even religion changes their views on things. I will stay with the PADI and DAN recommendations as a fairly safe and easy way to figure no fly times and tell someone with this dive/travel schedule they should not dive on the last day of the trip.

Thal do you have a different recommendations for the OP diving on the last day of his trip or do you agree with PADI and Dan on this?

 

[boulderjohn]

That's called an "appeal to authority," a classic logical fallacy, and let's not forget how accurate they were, and what the reasons were, when both organizations tried to vilify NITROX, "the devil gas."

You are actually not stating that correctly. The "appeal to authority" is only a fallacy when it is a false appeal to authority, when the authority does not actually have the credentials of an authority. From the link above:

This fallacy is committed when the person in question is not a legitimate authority on the subject. More formally, if person A is not qualified to make reliable claims in subject S, then the argument will be fallacious.

This sort of reasoning is fallacious when the person in question is not an expert. In such cases the reasoning is flawed because the fact that an unqualified person makes a claim does not provide any justification for the claim. The claim could be true, but the fact that an unqualified person made the claim does not provide any rational reason to accept the claim as true.​

 

[Thalassamania]

I can't think of an org in the world that hasn't changed an opinion on anything. Even religion changes their views on things.

Rarely do organizations change their opinions because they recognize that they were wrong in the first place. In my experience organizations like PADIand DAN only change the opinions that they came to hold for, shall we say charitably, other than scientific reasons, when they are called on them. NITROX being an excellent example. The Cayman Watersportsmans Association came out against it (turns out that was because they were worried that longer dives would upset the resort lunch and afternoon dive schedules). In response the Cayman Chamber responded in knee jerk fashion by stating that they would not know how to treat a NITROX DCS case and DAN and PADI lined up behind the Watersportsman. Not an micrograms of good science, all economics and politics. Cayman and company threatened to pull out of several major dive show if Brett and I were permitted to give our NITROX and Rebreather talks. The flying after diving recommendations smack of the same sort of crap. If the recommendations are conservative enough, the resorts have cover for not having to provide diving during the last 24 (or so) hours of a traveler's stay. As I said:

... let's not forget how accurate they were, and what the reasons were, when both organizations tried to vilify NITROX, "the devil gas."

I will stay with the PADI and DAN recommendations as a fairly safe and easy way to figure no fly times and tell someone with this dive/travel schedule they should not dive on the last day of the trip.

Thal do you have a different recommendations for the OP diving on the last day of his trip or do you agree with PADI and Dan on this?

I will tell you that if you sit out 24 hours it would be "better" and 48 hours would be even "better" than that. Seriously, will the OP be OK following the PADI/DAN recommendations ... absolutely. Will they be wasting a significant portion of their diving vacation? Yes they will. Are there ways to calculate more precisely and are there procedures for making the dive(s) with the same or less risk? Yes there are.

As I said initially:

There is no absolute, clear and simple answer. Is 9 hrs. enough? Is 12? Is 18? Is 24? Is two weeks? No one knows. All that can be said, with absolute assurance, is that the longer the time to the last dive the lower the odds of betting bent on your flight. So you need to understand the factors involved. If all my dives were relatively deep, short, no-D dives ... I would not be too worried about it, even with the last dive being 9m for 30 minutes. However, if I was filling up with nitrogen on long shallower dives during the previous days, and always entering the water with significantly reduced residual nitrogen time, well ... I'd be much more circumspect. If I had to make the dives, and I had to make the plane (and I have been in this sort of situation) my approach would be to use the highest oxygen mix that I could for each my dives (taking into account both MOD and the O2 clocks). I'd watch the available bottom time on my computer before each dive. If I saw that on the succeeding days my bottom time was significantly reduced I'd start using pure oxygen at extended safety stops (maybe 10 minutes or more? Again, watch your clocks). I'd surface breathe at least two hours of pure oxygen prior to getting on the plane. This is the sort of diving situation that just screams for a rebreather.

You are actually not stating that correctly. The "appeal to authority" is only a fallacy when it is a false appeal to authority, when the authority does not actually have the credentials of an authority. ...

John; an argument from authority requires two conditions: legitimate expertise and expert consensus.

You are referring only to the situation where the inference fails to meet the first condition (inexpert authority) however in this case, the second test, expert consensus fails (if just because both DCBC and I are recognized as "experts" on these questions and thus, clearly, no consensus exists).

Additionally, keep in mind that the argument from authority is an inductive-reasoning argument, so the truth of the conclusion cannot be guaranteed by the truth of the premises. It is fallacious to assert that the conclusion must be true, solely based upon the testimony of the authority. Such a determinative assertion is a logical non sequitur because, although the inductive argument might have merit, the conclusion does not follow unconditionally, in the sense of being logically necessary, e.g., the conclusion remains only an opinion, unsupported by examinable data or analysis.

 

[endurodog]

Your attitudes towards PADI and DAN are coming clearer. Orgs of all kind always make changes. I know of no static orgs be for profit or non profits. Everything changes for a variety of reasons be it legal, profit, someone in the org things it will be more efficient, be more attractive to the customers. Feeling like you do I can see why you have such a problem with those orgs, that's unfortunate.

So Thal are you saying the OP is safe to dive on the last day of his vacations with the hours he will have before flight? That was the orginal question.

 

[Thalassamania]

Your attitudes towards PADI and DAN are coming clearer. Orgs of all kind always make changes. I know of no static orgs be for profit or non profits. Everything changes for a variety of reasons be it legal, profit, someone in the org things it will be more efficient, be more attractive to the customers. Feeling like you do I can see why you have such a problem with those orgs, that's unfortunate.

No, honest is honest and once an organization is openly dishonest, it must win back trust. You were not privy to the inside workings of all this, I was, so I must operate on the basis of what I have observed, you are free to operate on the basis of what you believe, but it is better if you have some data. This was not the first time that I've seen each organization's officers behave in a cynical and self serving fashion, that put their personal needs ahead of truth or the needs of the diving community. Since the best predictor of future behavior is past performance; and I have yet to hear the mea culpa maxima from either that would be the first step toward wining back my trust, I take a jaundiced view of unsupported "recommendations" that have no basis beyond the logical fallacy of an appeal to authority. This is the decompression equivalent of a trust me dive made with a buddy that has proven untrustworthy in the past. Granted the CEOs have now changed, both Drew and Dan are old friends, but I remain disappointed that they have not come clean and set out on a clearly new and transparent path.

So Thal are you saying the OP is safe to dive on the last day of his vacations with the hours he will have before flight? That was the orginal question.

"Safe" means without risk. You can not dive without risk.

Can he dive on the last day and manage the risk every bit as well (or better) as the PADI/DAN recommendations would?

Absolutely.

That was my original answer.

 

[endurodog]

As expected.