vendredi 1 juillet 2016

Scuba diving and decompression sickness

I understand the physics behind decompression sickness from diving, what I don't understand is where the higher pressure factors in. Obviously I'm missing some trivial piece of information, or may understanding of pressure is wrong or something, but I can't seem to figure it out.

Wiki says:
"The prolonged exposure to breathing gases at high partial pressure will result in increased amounts of non-metabolic gases, usually nitrogen and/or helium, (referred to in this context as inert gases) dissolving in the bloodstream as it passes through the alveolar capillaries, and thence carried to the other tissues of the body, where they will accumulate until saturated."

But I don't understand how you are breathing gases at a high partial pressure (maybe I don't properly understand the term). The gas in the breathing tank is pressurized sure, but this is reduced to normal atmospheric pressure for breathing, as I understand it.

Basically I cannot see where in the process the air from the tank gets pressurised by the water around you? The air in the tank doesn't experience higher pressures (it's inside a pressure vessel). The air in your lungs doesn't experience higher pressures, because well, your body acts as a pressure vessel... so at what point is the air densified?

Please help. I know the answer has to be simple, but I can't seem to understand it and it's driving me nuts. I feel like a dumbass.


via International Skeptics Forum http://ift.tt/297qdWp

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