Curious Question - Wave action compared to ATA

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Basking Ridge Diver

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"When you breathe from a scuba tank, you breathe air at the same pressure as the surrounding water. This means that, although the water presses in on you, the air you breathe presses back out with the same force. This makes it easy to breathe. Breathing pressurized air under water is the same as you are breathing now. The air around you is pressing in on you from all sides, but it is not hard to breathe because the air you are breathing is pushing out with the same pressure as the air around you."

To make this question easier - if a 33 foot wave passes over head while on scuba - would that essentially change the ATA (adding 1ATA) or because it is moving does this alter/spread the overall pressure? I was curious only as a hypothetical question while on a safety stop and wave action occurs if you are holding a steady stop would the wave action cause you to fluctuate your "depth"?
 
I'm sure there's at least 1 additional atm of pressure while the wave is overhead, and possibly more if it were to "break" right over you. But holy cow, what are you doing diving with 33 ft waves?! Even Captain Quint would call the dive, no?
 
1. The air pressure coming out of the second stage, when it just comes out, is at around 10 bar/145PSI ABOVE ambient (this pressure depends on the specifications for the regulator).

2. A wave passing above you will alter the pressure but it does so for the time is passes over you which is a very short time. Your regulator will account for it. It does alter your depth in two ways, first increase the pressure as if you went down and then, at the tail end of it, the pressure goes down as if you ascended. The closer you are to the surface, the higher the rate of change in pressure and the more effect this passing wave will have on you.
 
If you're diving in 33' seas, I think you've got bigger problems than worrying about your atms. More realistically, consider 10' seas, which I have dove (and it was terrifying). The trough to crest is 10', but the median change is 5' (halfway between trough and crest). In terms of barometric changes, this is not a huge deal. If you're diving bigger seas than that, hats off to you!
 
1. The air pressure coming out of the second stage, when it just comes out, is at around 10 bar/145PSI ABOVE ambient (this pressure depends on the specifications for the regulator).

The pressure going INTO the 2nd stage, from the 1st stage, is 10 bar above ambient. The pressure of air coming OUT OF the 2nd stage is at ambient. Pressure within the 2nd stage body is also at ambient, or slightly above, depending on the location of the exhaust valve.
 
If it were at ambient pressure, it would just stop there and not move. The intermediate pressure is in the second stage and not just going into it.
 
If it were at ambient pressure, it would just stop there and not move. The intermediate pressure is in the second stage and not just going into it.

You are wrong. IP is in the hose, not in the 2nd stage. The flexible diaphragm and the exhaust valve ensure that only ambient pressure is possible in the 2nd stage. When you inhale, you decrease the pressure in your lungs, which causes ambient air from within the 2nd stage to fill your lungs, which lowers the pressure in the 2nd stage to less than ambient, which collapses the diaphragm, which pushes the lever, opening the valve, and air enters the 2nd stage until it reaches equilibrium with ambient.

Aren't you an instructor? I would have thought you'd know this.
 
The above is correct - the second stage delivers air at ambient pressure- the 140 psi above ambient pressure is from the first stage. A large wave passing overhead while diving would create a pressure change equal to the height of the wave (.445psi x height wave in feet). This pressure change would effect the first stage, second stage and pressure in the lungs.
 
1. The air pressure coming out of the second stage, when it just comes out, is at around 10 bar/145PSI ABOVE ambient (this pressure depends on the specifications for the regulator).
An instructor saying this?
 
The air pressure coming out of the second stage, when it just comes out, is at around 10 bar/145PSI ABOVE ambient
I sincerely hope not. 10 bar above ambient would pop my alveoli like soap bubbles.
 

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