minimum time before flying

[Gaucho]

Hello Doc, I hope this is the correct place to ask this.

Ive heard 48, 24 and 12 hours as an answer to this, but, am I OK to leave just over 12 hours surface time before I get on an airplane...? Im trying to arrange a trip to Cozumel and we are in a little disagreement in the group as to how long we need and this may kill a night dive we are planning. Thanks.

 

[DocVikingo]

Evening Gaucho,

DAN's (Divers Alert Network)position on flying after diving is: (1) A minimum surface interval of 12 hours is required before ascent to altitude in a commercial jet airliner (altitude up to 8,000 feet) & (2) Divers who plan to make daily, multiple dives for several days or make dives that require decompression stops should take special precautions and wait for an extended surface interval beyond 12 hours before flight. The greater the duration before flight the less likely decompression sickness is to occur.

As an aside, DAN's ongoing research on DCS indicates that divers increase their risk of DCS if they fly within 17 hours of their last dive when there have been multiple dives.

In short, 12 hours would be cutting it short.

DocVikingo

 

[Gaucho]

Thanks Doc. I will build in a minimum window of 18 hours.

 

[greg somers]

You are essentially dealing with 2 ascents.The tables are worked out at sea level where the pressure is 14.7psi.
After 12 hours SIT you can start again...but that's at sea-level.The height of the plane puts you in low pressure.In fact most planes as I'm aware have an internal pressure of 8000ft,and the air is dryer than any desert in the world.
(I just read that today).Any container that has a higher pressure inside it will always try to get out...ie a soft drink bottle or champagne.If you come up too quickly in water than the nitrogen will quickly come out of solution to equalise with the outside pressure.That's why we come up slowly.But in a plane that is not so.You go up AGAIN EVEN MORE and QUICKLY.it's like 2 dives at the same time.You cannot use the sea-level figures for altitude.That's why there is separate tables for altitude diving.
The fact is that flying puts more stress and major dehydration on the body which also primes it for DCS problems.It may only affect 1 in 20,but what if you are that one? Or someone you love?
To make it easier the agencies have wisely treated them as 2 SIT times (2 x 12 hours) which in my view is wise.Don't try for 18 hours.Be safe and go for 24 hours.
Have fun on the trip but plan to return to us.
Cheers hoping you're listening ears,
The Gasman

 

[DocVikingo]

Hey greg, exactly what kind of gas are you huffing from that tank?

Wink.

DocVikingo

 

[Dr Deco]

Dear Gaucho:

The other readers have responded with sage advice. The longer SI the better. In principle, it should be able to calculate gas loads from multiple dives and then calculate the proper surface interval. Many people have wondered why dive computes typically do not do this. One problem is a lack of data as to what constitutes a safe interval for an ascent to 8,000 feet.

This aspect is one of the DAN research projects. We looked at a very specific case for one NASA use and found that it was not a simple and straightforward process to optimize. That is something for the future.

Dr Deco

 

[Gaucho]

Thanks to all. I will plan accordingly.

 

[greg somers]

I can (stumble,stumble,hick !) handle it......(crash @$#%!)