jhelmuth once bubbled...
I'm sorry, but I can't believe you are serious. When you fly, you do not off gas more nitrogen than on the ground. Why? Because you haven't loaded more nitrogen at 1 ATM and the cabin pressures maintained throughout a flight are not significantly less than 1 ATM to cause a metabolic change in any "normal" nitrogen blood levels. Even so, if you did you would have no diffaculty in loading once in the water.
<snip>
Really - all the same rule apply, but not differently than being on the ground!
Um...
Nope...
You are normaly "saturated" with nitrogen at sealevel to a PP(partial pressure) of approximately .79
When you dive, your tissues absorb more nitrogen due to the increased PP of the nitrogen that you are breathing at depth.
You absorb some oxygen as well, but much of the oxygen is burned up by metabolic processes so it isn't generaly an issue contributing to DCI.
On a plane trip, you ARE subject to LESS than 1 ATM pressure. If you were kept at 1 ATM the whole trip, your ears would never pop in an airplane.
Most airlines keep cabin pressures approximately equivalent to 5-7 thousand feet altitude. 2 of the reasons for this are that 1 ATM cabin pressure at 32,000 feet would put more stress on the airframe and AIR IS HEAVY. They don't want to pay for the fuel to haul more pressurized air through the sky than is really needed for passenger comfort and safety.
For example: a 747 carries many TONS of air in the cabin that must be accounted for when calculating the weight of the aircraft at altitude to figure fuel consumption.
In any case, YOU DO OFFGASS when flying in a pressurized aircraft over 6000 feet off the ground.
Just not very much.
If the flight were long enough, you would eventualy reach nitrogen "saturation" for the cabin pressure (same as if you climbed a mountain to 6000 feet and stayed for a while) and begin to ONGASS when you landed (or came back down the mountain).
It's for this very reason that some dive computer manuals reccomend that you DON'T TURN THEM ON during a flight or they might think a dive has begun when the plane descends for landing.
Then they are stuck in divemode untill you get on another plane and ascend to 'finish the dive' or pull the battery to reset the computer. I've personaly seen this happen to another divers computer.
You should also NEVER PUT THEM IN CHECKED BAGGAGE. The reduced pressure and extreme cold in the cargo hold (non-pressurized compartment on most aircraft) can damage some types of pressure sensors used by certain dive computers. Besides, you don't want what may be yor most expensive piece of dive gear thrown around by baggage handlers and burried under many other bags and boxes in the hold do you?
Some, like the cochrans, will even track the amount of offgassing from the reduced pressure of the flight and credit you on the first dive a tiny amount if the dive is soon enough after the flight and you havn't "theoreticaly" resaturated to sealevel yet...
