28 Hours of No Fly Time?

[tursiops]

Apparently what you are missing is what I actually said. The OP asked if flying after 24 hrs is safe. The answer is that it's hard to argue that it isn't. What am I missing? If lots of computers say 24 hr is safe, then it's hard to argue that 24 hrs is not safe.

I guess we need to dig just a bit deeper here. You are arguing that if lots of computers say something, then it is probably true. And therefore it is hard to argue with.
But two things:
(1) those computers are just using a 24h timer, because DAN or someone said 24h was often pretty good. so it isn't really that lots of computers are saying something independently....they are just quoting the same thing over and over. that is not additional information, that is just repetition of the same thing. In weather forecasting, for example, we get an extra day or two of decent forecast because many different models are being used...and the ensemble average is used to make the final forecast. The key is that the many different models are all different, not that they are the same thing just run over and over.
(2) His computer said 28h, and it is the only one of all those sources that actually knows what that diver did. Shouldn't it be given some more credence, be weighted more heavily, when deciding if 28h is safer than 24h?

 

[seeker242]

I guess we need to dig just a bit deeper here. You are arguing that if lots of computers say something, then it is probably true

What I'm saying is it's difficult to argue that all those other computers are unsafe. Because if you are going to argue that 24 hr is not safe, then you are arguing that all those other computers are unsafe. But, tons and tons of people fly that way with those computers and it doesn't cause problems.

because DAN or someone said 24h was often pretty good. so it isn't really that lots of computers are saying something independently...

Precisely. So, if you are going to argue that 24 hours is not safe, then you are arguing that DAN is just wrong. You are arguing that PADI is just wrong. Therefore, it's quite difficult to argue that DAN is giving unsafe recommendations. It's quite difficult to argue that PADI is giving unsafe recommendations. It's quite difficult to argue that the whole dive industry is giving people unsafe recommendations.

His computer said 28h, and it is the only one of all those sources that actually knows what that diver did. Shouldn't it be given some more credence, be weighted more heavily, when deciding if 28h is safer than 24h?

More credence, sure give it more credence but the question you just stated was NOT the question that was asked. Here is the question that was asked:

"Should I feel safe following the 24-hour (conservative) guideline and flying home tomorrow?"

Notice it does NOT say "Is 28 safer than 24? That's not the question to begin with so that question isn't even relevant.

 

[tursiops]

Precisely. So, if you are going to argue that 24 hours is not safe, then you are arguing that DAN is just wrong. You are arguing that PADI is just wrong. Therefore, it's quite difficult to argue that DAN is giving unsafe recommendations. It's quite difficult to argue that PADI is giving unsafe recommendations. It's quite difficult to argue that the whole dive industry is giving people unsafe recommendations.

[Mod edit] What I said was even if tons of computers say 24h, that is irrelevant, because they are all just quoting DAN, who along with PADI is just quoting the consensus workshop.....which said 18h, and it said 24h, and it said longer in some circumstances. So the issue is not "tons of computers," it is the DAN-sponsored workshop, which has lots of caveats in it. DAN is not wrong, it is just not making an absolute statement, like you seem to want. And they are ALL just recommendations....so we have an OP who happens to ahve a computer that does NOT give the DAN simplistic one-number result; what should he do? Thus the next quote:

Notice it does NOT say "Is 28 safer than 24? That's not the question to begin with so that question isn't even relevant.

If you read a bit more of what he said in later posts, he is concerned that his computer said 28 and DAN says 24, and the disparity bothers him. Correct, he did not say that in your excerpt from his original post, but he certainly did later.

Now, you and I both think that 24 is fine, thus 28 is fine. Maybe 28 is safer than 24, but that does not make 24 unsafe. 48 would also be safer than 24, and is in fact often the recommendation if flying to altitude, like Denver.

 

[Stoo]

Just pop your head into the cockpit as you board and ask the pilot to "Keep 'er low". They do that all the time coming back from diving hot-spots. It gets interesting as you approach the southern coast of the US. Get a window seat and keep your camera handy.

Seriously, you'll be fine. After 24 hours you'll have so little extra gas in you that an extra 4 hours wouldn't even register.

 

[rsingler]

---

---

A ScubaBoard Staff Message...

A significant number of irrelevant posts were just deleted. Bickering is of little interest to anyone. Let's try to stay on track here...
The OP asked for info just before potentially boarding a flight. He got some info, and also some criticism over the medical validity of armchair advice. There were some assertions made, and a nice analysis of how some computers calculate no-fly time! What else we got here?
Let's keep SB the fascinating place it usually is! And remember, this is the Basic Forum, where new divers congregate. There are special rules for this forum.

---

 

[Neilwood]

I am diving on a Suunto Eon Core. After my last dive of the trip earlier today, I surfaced with my watch showing a "no fly" time of slightly more than 28 hours. My flight is at 4 p.m. tomorrow, at which time I will be almost exactly at 24 hours. All of the guidelines I have seen, and some of the prior discussions here at Scuba Board, indicate that 24 hours is a good and safe rule of thumb for no-deco recreational divers (and generally seen as a conservative one at that), and that some guidelines (e.g., DAN) suggest even less time before flying.

As background, I have been diving the last 3 days – 2 dives today, 3 dives yesterday, and 3 dives the day before yesterday. All have been fairly conservative profiles – nothing close to deco. Maximum depths today were 78 feet on dive #1 and 89 feet on dive #2 (about 22 minutes were spent near the bottom, mostly between 75 and 80 feet, and then a gradual ascent with a length period of time spent in the shallows).

"No fly" time on my Suunto after my first dive today was 24 hours, which had reduced to about 20 hours after my surface interval, before exceeding 28 hours after my second dive. I recall that the "no fly" time similarly jumped to about 28 hours earlier in the trip after a different day of repetitive dives.

I have heard Suuntos are conservative. Should I feel safe following the 24-hour (conservative) guideline and flying home tomorrow? Or should I miss my flight to comply with the computer? (Note – I am in Bonaire, so not that easy to just hop on the next plane.)

I am thinking the watch is just being overly conservative and the 24-hour rule is safe, but I am cautious by nature. Any advice would be appreciated.

I am purposefully ignoring all the back and forth between certain people and answering your OP (already posted a reply but not 100% related to the OP).

The guidelines from DAN are 18hrs (based on the flying after diving workshop ) however they believe that 24Hrs is "probably safe" - link. Nowhere in the latest review do the suggest that the 24 hr period requires review (which seems to be alluded to by a number of posters) however they suggest longer is better (which no one would dispute).

On that basis, I would be happy to fly after 24hrs after doing repetitive multi NDL dive days. Your computer might suggest more but that does not seem to be backed by the scientific research and reviews. 28hrs would be great but 24hrs, on the basis of the recommendations for NDL diving, is sufficient. For decompression diving, longer is definitely advised.

 

[John C. Ratliff]

Ok, since everyone else has already gone off the rails, I can happily add my piece of survivor bias. On my last tech dive trip, after 6 consecutive days of decompression diving to 50-52 meters (165-172ft), I was on a plane home some 8 hours after surfacing from the last dive. So was my buddy.

Neither of us died, nor got hurt, nor grew any extra pairs of eyes. I intend to do it again.

Now more seriously (disclaimer: dont take the advice literally, I’m not responsible for you).. commercial passenger aircraft must maintain a minimum of cabin pressure equivalent to 2400m altitude (approx 8000 ft). That equates to about 0.75 atmospheres. So you can do the math, or ask your deco program to do it. Let’s say you surface with the most loaded compartment at 85% of its m-value, and add a short surface interval of lets say 4h-6h, in my books you would probably be fine in any case, Thats because tissue half times are between 4 and 700ish minutes, and you”d have to do some hardcore stuff to get the slow tissues fully loaded, so likely some midway compartments will be leading. So the extra 4-6 hours will give you a big buffer to make it to 0.75atm. And unless you talk bush taxi or own plane, you wont make it faster than 4-6h from the water to the plane, incl drying off, packing gear, checking in and clearing security.

Now in the case of loss of cabin pressure at altitude it might be a different story, but first thats very unlikely and secondly you then have another set of problems at hand to begin with.

Actually, you don't yet know wether you were injured or not. Ever heard of aseptic bone necrosis? This is a disease of the bone that you'll not discover for years after the original injury, when the bone breaks unexpectedly.

SeaRat

PS, I just found this off a Facebook post on their SCUBA Accidents and Incidents page.
Flying After Diving: Finally, the Facts (Not Just Theory)

 

[BRT]

Actually, you don't yet know wether you were injured or not. Ever heard of aseptic bone necrosis? This is a disease of the bone that you'll not discover for years after the original injury, when the bone breaks unexpectedly.

SeaRat

PS, I just found this off a Facebook post on their SCUBA Accidents and Incidents page.
Flying After Diving: Finally, the Facts (Not Just Theory)

I've had it. The bone doc had no idea it could be caused by diving.

 

[BlueTrin]

I've had it. The bone doc had no idea it could be caused by diving.

So what’s the recommendation to avoid it ?

 

[BRT]

So what’s the recommendation to avoid it ?

??? Stay away from NDL's. I had never been "in deco" but often pushed the limits. Now I dive nitrox if I can, and this lets me stay further away from NDL's. I consider that a good thing but others think nitrox is a waste if the dive can be done while not exceeding NDL's. Mind you, I have no proof that my necrosis was from diving, but it fit.