Eli5. Why does the compression change in breathing compressed air at different depths? Surely the ‘oxy-mix’ metal container doesn’t physically ‘compress’ any further than it has in 1atm (unless at near Hadal Depths)

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Im obviously confused somewhere. But let me explain further.

You have a metal container, carrying your breathable gas mix (depending on your depth). If this container doesn’t actually physically compress further due to the rigidity of the metal at say 800ft, then why would breathing a 80-20 mix of Ni and O in a compressed container cause any effects?

I understand that free diving, or diving in mailable suits will obviously cause your body to compress under the weight of the water around you. But saturation divers are very different. Are they not safe from the ‘physical’ pressure of the water, yet unsafe from the compression of air? What is the difference between our bodies not compressing at this depth, compared to the oxygen in our lungs compressing?

Edit: another question. If the oxygen inside the container is already at an extreme pressure, then why would releasing it cause any change to us physically from breathing it at sea level, compared to 1mile under the sea?

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Anonymous 0 Comments

The container is usually at a very high pressure, when full at least. Normal SCUBA cylinders operate around 200 bar (200 times atmospheric pressure. You can’t breathe that directly, I hope I don’t need to explain why…

So, SCUBA tanks have a “regulator” at the mouthpiece. This controls the pressure which is delivered from the tank to the mouthpiece. At the surface, the air pressure coming out of the mouthpiece is more or less the same as the surrounding atmospheric pressure. Let’s say the tank holds enough air for you to breathe for 1 hour on the surface. If you descend 10 meters, the surrounding water pressure is now double what it was at the surface. The regulator delivers air to the mouthpiece at this same local pressure, i.e. 2 bar. You now only have enough air for 1/2 an hour, if you stay at 10 meters.

I’m not sure if I have really answered your question, but I hope I have at least made a start.

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