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 air in a SCUBA tank is at extremely high pressure, typically around 200 atmospheres (3000psi). The diver breathes through a regulator, which regulates the air pressure down to match the pressure of the surrounding water.

It is necessary for the pressures to be equal – if the gas was regulated down to surface pressure, the diver would be unable to inhale because of the pressure difference. So the deeper a diver goes, the higher the pressure of the gas they’re inhaling.

However, at elevated pressures, gases can have different effects on the body. Below a depth of about 30m, the nitrogen that makes up most of ordinary air can cause [nitrogen narcosis](https://en.wikipedia.org/wiki/Nitrogen_narcosis), which has effects somewhat similar to drunkeness. Divers going deeper than this will often breath alternative gas mixtures, such as helium and oxygen.

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