Would you dive if you flew out within 24 hours?

[DandyDon]

"a minimum surface interval of 12 hours is required to be reasonably assured a diver will remain symptom free upon ascent to altitude in a commercial jet airliner pressurized to an altitude of 8000 feet"
"a surface interval of 18 to 24 hours is recommended after daily multiple dives over several days or dives that require decompression stops. the greater the surface interval before flight the less likely DCS will occur.
"DAN makes the point that there can never be a flying after diving rule that is garanteed to prevent DCS completely. rather, there can be a guideline that represents the best estimate for a conservative, safe surface interval for the vast majority of divers. there will always be an occasional dive whose physiological makeup or special diving circumstances wil result in DCS."


this was taken directly from my SSI training course material that i am currently studying......decide for your self.

That's difficult to do with your typos. Google found No results found for "surface interval of 18 to 24 hours is recommended after daily multiple dives" so I don't know what you got from where.

DAN does not have a 24 hour rule.

 

[Steve_C]

Historically the dive tables were done on young males in excellent shape. As an older (67) modest shape diver I need to keep that in mind. Also airline flights are not all the same. I believe the cabin pressures between airlines can vary by up to 1000 ft. Also top altitude can easily vary over about 5,000 ft. Its all approximations. Bottom line, the flight ain't fun if each little twinge has you worried about DCS.

---------- Post added January 20th, 2013 at 10:14 AM ----------

Historically the dive tables were done on young males in excellent shape. As an older (67) modest shape diver I need to keep that in mind. Also airline flights are not all the same. I believe the cabin pressures between airlines can vary by up to 1000 ft. Also top altitude can easily vary over about 5,000 ft. Its all approximations. Bottom line, the flight ain't fun if each little twinge has you worried about DCS.

---------- Post added January 20th, 2013 at 10:16 AM ----------

PADi Encylopedia of diving. Page 5-78. Gives DAN min of 12 hours. 18-24 hours after decompression dives. Cites studies after multiple dives showing that up to 17 hours was needed which sounds like 18 hours.

---------- Post added January 20th, 2013 at 10:23 AM ----------

By the way to put the risk in perspective suppose that something bad has a 1% chance of occurring during an activity and that risk is independent of previous experience. Suppose that I do the activity 50 times. Then there is a 39.5% chance that something bad will happen to me during the 50 dives. [ (.99)^50 = 60.5 is probability of never having bad ). With 20 trials it is about 18%.

 

[BDSC]

I'd do the dive even with 10 hours between the dive and flying. Do the dive! It may be the one when the whaleshark swims by!!!!!!

 

[Quero]

Historically the dive tables were done on young males in excellent shape. As an older (67) modest shape diver I need to keep that in mind. Also airline flights are not all the same. I believe the cabin pressures between airlines can vary by up to 1000 ft. Also top altitude can easily vary over about 5,000 ft. Its all approximations. Bottom line, the flight ain't fun if each little twinge has you worried about DCS.

Steve, we're not talking about dive tables here. We're talking about DAN airborne-ascent-to-altitude recommendations which were derived from clinical studies. These recommendations are relatively recent. They are not historical guidelines based on fit young sailors. We're talking about recommendations made barely ten years ago with recreational divers in mind. Furthermore, the cabin pressurization used in the studies was the minimum stipulated by FAA regulations--8000 feet--so that the recommendations would be conservative.

By the way to put the risk in perspective suppose that something bad has a 1% chance of occurring during an activity and that risk is independent of previous experience. Suppose that I do the activity 50 times. Then there is a 39.5% chance that something bad will happen to me during the 50 dives. [ (.99)^50 = 60.5 is probability of never having bad ). With 20 trials it is about 18%.

That's not how probability works. Each time it's the same theoretical 1% chance. Relative frequency is the number of incidents actually recorded over a number of trials, so if a diver did two dives only and was bent on one of them, his relative frequency for getting bent would be 50%. Based on the statistical evidence in the clinical trials, we can say that the more dives a diver does with no bends, the closer he will progressively get to the the expected 1% probability if he ever does get a bend. I've done thousands of dives and have never been bent. So if I ever do take a hit, my relative frequency will be well below 1%.

 

[Christi]

"a minimum surface interval of 12 hours is required to be reasonably assured a diver will remain symptom free upon ascent to altitude in a commercial jet airliner pressurized to an altitude of 8000 feet"
"a surface interval of 18 to 24 hours is recommended after daily multiple dives over several days or dives that require decompression stops. the greater the surface interval before flight the less likely DCS will occur.
"DAN makes the point that there can never be a flying after diving rule that is garanteed to prevent DCS completely. rather, there can be a guideline that represents the best estimate for a conservative, safe surface interval for the vast majority of divers. there will always be an occasional dive whose physiological makeup or special diving circumstances wil result in DCS."

this was taken directly from my SSI training course material that i am currently studying......decide for your self

i think the bottom line in any diving situation, including this one, is this........first and foremost.......always dive within your training limits and your own comfort zone. never follow someone else recommendations. especially if they are basing those decisions on advanced level training that you yourself have not taken.
is it ok for a fully trained cave diver to enter the "no light zone" to explore an area of a system that is off limits to most of us ?? based on their training and experience, probably "yes". at least they have made a calculated decision on what risk level they are comfortable with. but is it also ok for me as an open water cert diver to follow that same cave diver into that same area if he says to me....."it's ok. just follow me and you will be fine." i would think we could all agree that answering "no" to that scenario is the only answer.
maybe my point is a bit dramatic but the issue is the same. my training up until this point has always been to wait 24 hrs before flying after any diving. and that is what i do. period !! now perhaps once i complete my current training and understand better how nitrogen absorption and off gassing really works at a physiological level, i might decide that i can reduce my no fly time to 18 or even 12 hrs depending on my situation. but as of right now, i am a typical average recreational diver. and my training and comfort level tells me to wait 24hrs. the OP should follow their training and do what is comfortable for them. imo, if they are asking the question, they already know the answer. i say this in my real job at home all the time to the new guy i am training........if you have to ask, "should i be doing this ??"......then the answer is always NO.

so to the more advanced divers here on the boards......i think it is great to share your knowledge and experience with the rest of us so the dive community here benefits from it. but please remember that not every one fully understands the science or theory behind a lot of your decisions. so even though you may be technically correct in advising the OP it is ok for them to have an SI of a shorter duration, keep in mind the point i have tried to make.

Taken from your SSI training manual - but not taken from DAN's website! This is DIRECT from DAN's website, not an interpretation from an agency training manual.

Scuba Diving Medical FAQ Articles ? Decompression Illness ? DAN | Divers Alert Network

Revised Flying After Diving Guidelines for Recreational Diving - May 2002The following guidelines are the consensus of attendees at the 2002 Flying After Diving Workshop. They apply to air dives followed by flights at cabin altitudes of 2,000 to 8,000 feet (610 to 2,438 meters) for divers who do not have symptoms of decompression sickness (DCS). The recommended preflight surface intervals do not guarantee avoidance of DCS. Longer surface intervals will reduce DCS risk further.

• For a single no-decompression dive, a minimum preflight surface interval of 12 hours is suggested.
• For multiple dives per day or multiple days of diving, a minimum preflight surface interval of18 hours is suggested.
• For dives requiring decompression stops, there is little evidence on which to base a recommendation and a preflight surface interval substantially longer than 18 hours appears prudent.

There is a lot of extra verbage in your SSI manual that claims to be from DAN - but I don't see it anywhere - in fact - they claim (which I agree) the ONLY guarantee to prevent DCS is not to dive period.

What you posted is SSI's interpretation of the DAN recommendations, which have actually been 12 - 18 hours for over a decade. As Don said - the "24 hour" belief/theory still sticks in some people's heads - and people still have such tunnel vision to say "I can't dive the day before my flight" without really thinking about it or actually considering the flight time.

For example, here in Cozumel - we don't have any flights leaving the island before 11:30am - unless someone is taking the puddle jumper over to Cancun to fly out. In these cases, people who have been diving all week can STILL safely dive the day before their flight out according to DAN's recommendations. A two-tank morning dive departs around 8:00 and divers are out of the water and back on the boat by noonish - that still gives well over the 18 hour recommendation - in fact, it gives them 23.5 hours if they are on that first flight out - over 24 hours if they are on the 1:30pm flight out!

Many of you are also not reading what the OP actually said about his dive profile. He was looking at a SINGLE 30 minute dive to 60 feet after 48 hours +/- surface interval since his last set of dives - two dives, 60 feet max for a total bottom time of just over an hour between TWO dives - very conservative profile at that! So the dive he was contemplating clearly qualified under DAN's guidelines as a single no decompression dive!

Too many people are under the very false notion that if they follow their tables or their computer perfectly that they can't get bent are really in la-la land - and I would advise doing some serious research on the topic. AS someone who has been diving for almost 20 years, with 2000+ logged dives, and has had TWO serious DCS hits in the past 10 years (2002 and 2011), neither of which I did anything "wrong" = undeserved/unexplained hits - I am telling you - the only way to guarantee not getting bent is not to dive. Otherwise, dive safe and often, stay current on your training and skills, hydrate, be well rested, etc. and your risk of DCS is no greater or less than getting in your car and having an accident.

 

[dpaustex]

Lots of good points.

The recommendations of the dive agencies, and DAN, are just that - recommendations.

There are a lot of variables in the "causes" of DCI/DCS.

A person's physical "fitness", as well as their lung "fitness'. A fit "looking" person could be thin as a rail, but be a heavy smoker, having had a recent lung disease (e.g. bronchitis, etc), could be dehydrated....you get the idea.

The overall increase in nitrogen loading varies between the "fast" and "slow" tissue rates (some tissues expel the nitrogren faster than others). Is the person overweight? Fat tissues tend to hold it longer.

As pointed out by others, aircraft, and companies, tend to only partially pressurize their planes. I think it was pointed out that the equivalent pressure is around 8000 ft MSL for many companies in commercial jets.

As also pointed out, the "guidelines" say wait 18 hours for a repetitive dive series. Again, the are many factors which affect off-gassing, in terms of the rate, what type of residual did you have, etc.

Having said all of that; if you're in shape, have good aerobic function, are well-hydrated, otherwise fit, and follow the dive profile you stated, I'd probably dive.

But of course, that's me, and I know what my factors, above, are...so you have to make your own call.

 

[BDSC]

For example, here in Cozumel - we don't have any flights leaving the island before 11:30am - unless someone is taking the puddle jumper over to Cancun to fly out. In these cases, people who have been diving all week can STILL safely dive the day before their flight out according to DAN's recommendations. A two-tank morning dive departs around 8:00 and divers are out of the water and back on the boat by noonish - that still gives well over the 18 hour recommendation - in fact, it gives them 23.5 hours if they are on that first flight out - over 24 hours if they are on the 1:30pm flight out!

Christi,

I have always wondered why almost every dive shop/operator always price their week of diving as "5 days of two tanks". Of course I know you can always add to that but it seems that the standard week of diving in Cozumel is the 5-day/2-tank schedule. Any particular reason for that? Maybe a hold over from the old days of the 24 hour rule?

 

[drrich2]

my training up until this point has always been to wait 24 hrs before flying after any diving. and that is what i do. period !! now perhaps once i complete my current training and understand better how nitrogen absorption and off gassing really works at a physiological level, i might decide that i can reduce my no fly time to 18 or even 12 hrs depending on my situation. but as of right now, i am a typical average recreational diver. and my training and comfort level tells me to wait 24hrs. the OP should follow their training and do what is comfortable for them. imo, if they are asking the question, they already know the answer. i say this in my real job at home all the time to the new guy i am training........if you have to ask, "should i be doing this ??"......then the answer is always NO.

so to the more advanced divers here on the boards......i think it is great to share your knowledge and experience with the rest of us so the dive community here benefits from it. but please remember that not every one fully understands the science or theory behind a lot of your decisions. so even though you may be technically correct in advising the OP it is ok for them to have an SI of a shorter duration, keep in mind the point i have tried to make.

I get your point, but there's an irony in your reasoning. You waited 24 hours not because of your understanding of how nitrogen absorption and off-gassing really work at a physiological level, but because an agency you presumed trustworthy told you that figure. They could've told you 30 hours or 16 hours and you'd have bought it hook, line and sinker.

Now, DAN (as trustworthy an agency as we're likely to hear from) has provided a more liberal regulation that appears to provide an adequate and conservative margin of safety, and lets us get more dives in.

Richard.

 

[Christi]

Christi,

I have always wondered why almost every dive shop/operator always price their week of diving as "5 days of two tanks". Of course I know you can always add to that but it seems that the standard week of diving in Cozumel is the 5-day/2-tank schedule. Any particular reason for that? Maybe a hold over from the old days of the 24 hour rule?

It's simply a package option - nothing more, nothing less. Not everyone comes for an entire week. I have 3, 4 5, 6 and 7 day packages posted on my website - but I can customize a dive package for any divers trip - I just need to know how many days they want to dive and I can do it. There is nothing set in stone - maybe alot of shops just provide the most popular option - we can't list every possibility

 

[rick00001967]

I get your point, but there's an irony in your reasoning. You waited 24 hours not because of your understanding of how nitrogen absorption and off-gassing really work at a physiological level, but because an agency you presumed trustworthy told you that figure. They could've told you 30 hours or 16 hours and you'd have bought it hook, line and sinker.

Now, DAN (as trustworthy an agency as we're likely to hear from) has provided a more liberal regulation that appears to provide an adequate and conservative margin of safety, and lets us get more dives in.

Richard.

you are absolutely correct. and you actually made my point for me. i do not have enough scientific understanding of nitrogen loading and off gassing. it is all "theory". everyone is different. even christi said she got bent 2 times and she did nothing "wrong". so yes, i will follow what i was taught to do. if that means i "fell for it hook line and sinker", then so be it. i have never had a problem scheduling my dives to give me 24hrs before leaving. and until i have the knowledge and experience that will allow me to make a different choice, i will stick to 24hrs.

---------- Post added January 20th, 2013 at 05:28 PM ----------

That's difficult to do with your typos. Google found No results found for "surface interval of 18 to 24 hours is recommended after daily multiple dives" so I don't know what you got from where.

DAN does not have a 24 hour rule.

i apologize for my typing mistakes. i will try harder next time.

as far as the quote i posted......i was only trying to add relevant info to the discussion (which i am finding very interesting btw). that statement is a direct quote from the SSI "science of diving" manual.

i am not saying it is right or wrong. that is beyond me to make a judgement like that. it simply is what it is.

---------- Post added January 20th, 2013 at 05:33 PM ----------

......any more than a certified cave diver is going to provide inappropriate advice here (I don't know where that came from but wanted to reference it). Most of us recognize that you need to get the training in a class.

no offense was intended towards anyone who is a cave diver. i was only trying to make a point about following your own training and not relying on someone else to make that decision for you. sorry if anyone took it the wrong way.


btw......there may be another reason i believe dive ops (at least all of the ones i have ever used) suggest a 24hr wait. would it not make sense that a dive op would rather advise its customers to wait the 24hrs rather than telling them it is ok to only wait 12 or 18 (depending on the circumstances). is there not a possible liability issue here. if some rookie diver comes down to mexico for a week of diving for example, is it not prudent to recommend a longer wait time rather than the "minimum" wait time.
as someone who is hoping to be a dive con at some point in the future, i know i would feel much better knowing my student or my stores customer was taking the best precautions, and not just doing the "minimum".
but seeing as i am not a dive pro, maybe i am way off on this one ?? many here would have a better perspective on this than i would.