Hypothetical question

[boulderjohn]

I heard about (but did not see) a hypothetical question posed on another forum, and I thought I would try it here to see what kind of a response it gets. Ideally, you would read the question, post a response, then explain your reasoning in the thread, along with responding to other people's thoughts.

The Question: Someone tells you that he or she needs to do a 90 minute dive to a maximum depth of 9 meters/30 feet using 60% nitrox. This person wants to know how long he or she should wait before flying on a commercial airline. What is your answer, and why?

 

[Danseur]

No N2 ongassing occured. In fact, offgassing has occured. Safe to fly.

 

[АлександрД]

he or she needs to do a 90 minute dive to a maximum depth of 9 meters/30 feet using 60% nitrox. This person wants to know how long he or she should wait before flying on a commercial airline

6 hrs. Just in case
In real - no need, because for this depth and time you will not obligate too much for slow tissues, and time to airport, than registration, etc - will over 3 hrs...
Above is just my NON specialist opinion, just personal estimation.

 

[tmassey]

At 2 ATA (33 ft), 40% nitrogen becomes the same pressure as 80% nitrogen at 1 ATA. Close enough: they’re breathing atmospheric level of inert gas. Fly away.

 

[bmorescuba]

I'm not trying to be snarky at all, but reading the question carefully. If someone came to me and asked advice, I have to consider that my certification level as a DM carries with it higher potential liability. Therefore, even though I would feel safe immediately hopping on a plane after this dive profile, I would tell someone else to wait 18 hours, since that recommendation is backed by DAN and the industry in general (for single dives).

 

[Storker]

9 meters on EAN60 is a pPN2 of 0.76 bar.

Personally, I wouldn't have any issues flying after a dive like that. If my answer has had any liability, I'd recommend following PADI's guidelines about flying after diving.

 

[Diver0001]

Well... the EAD is 4.5 meters so there is no chance of DCS. You should be able to get out of the water and step on an airplane with your hair wet.

The other side of the discussion is that the recommendations are what they are and even though there is no risk, I suspect that most people would be uncomfortable not following the recommendation.

Incidentally, when I started diving the recommendation for flying after diving was to be a "D" diver on the PADI table we had at the time. A lot has changed.

R..

 

[J-Vo]

No problem. Fly away.

 

[EireDiver606]

No waiting as there’s no risk realistically

 

[Storker]

the EAD is 4.5 meters

Care to show your math? EAN60 is 40% N2. 9m is 1.9 bar ATA. That gives a pPN2 of 1.9x0.4=0.76. Surface pPN2 of air is, last time I checked, 0.79 bar. Roughly.