Question What's your safety stop depth?
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That is not true if you are on oxygen. Staying deeper than 10 feet while on oxygen has the added benefit of being at a greater ambient pressure and this less chance of bubble growth or development.
50-50
Yes, we can ascend to a shallower depth where off-gassing is faster, and hence bubble formation is also greater.
Or we can stay deeper, where off-gassing is slower, but also bubble formation is less.
In this tug-o-war one needs to find the optimum.
Are you telling me that you off-gas faster at 10 feet because the PPN2 in oxygen is less at 10 feet than at 20 feet? I would think that the partial pressure of nitrogen in what you are breathing will be about the same at any depth if you breathing pure oxygen.
For people who are confused about this.....
When we descend on a dive, our lungs which would normally be compressed to a smaller size by pressure instead stay full-size because we breathe in compressed air and are inhale more molecules of the gases. to fill the space. If we descend to 99 feet/10 meters of sea water, we are under 4 atmospheres of pressure, so we multiply the percentage of nitrogen in the mix we are breathing by 4 to see what we inhale with each breath. If we are breathing air, the nitrogen has a partial pressure of 4 * 0.79 = 3.76. Since this is more than the nitrogen pressure in our body, nitrogen enters our tissues and increases the nitrogen pressure there.
That is the advantage of breathing nitrox. If we breathe 32% nitrox on such a dive, the nitrogen partial pressure is 4 * 67 = 2.68, so we take on less nitrogen.
As we ascend, the total pressure drops, and the nitrogen partial pressure drops, too. When it is less than the pressure in our tissues, we begin to off-gas nitrogen from those tissues. Technical divers like to accelerate that by breathing stronger and stronger nitrox mixes to get the biggest possible difference between the nitrogen pressure in the body and the nitrogen pressure in the mix we are breathing.
At 20 feet, it is considered safe to breathe pure oxygen. When they do, there is no nitrogen in the mix, so the partial pressure of nitrogen is zero. With any air or nitrox mix, the shallower you are, the greater the pressure difference. Once you are no longer breathing any nitrogen, though, it doesn't matter any more. The nitrogen partial pressure in pure oxygen is zero at any depth.
When we descend on a dive, our lungs which would normally be compressed to a smaller size by pressure instead stay full-size because we breathe in compressed air and are inhale more molecules of the gases. to fill the space. If we descend to 99 feet/10 meters of sea water, we are under 4 atmospheres of pressure, so we multiply the percentage of nitrogen in the mix we are breathing by 4 to see what we inhale with each breath. If we are breathing air, the nitrogen has a partial pressure of 4 * 0.79 = 3.76. Since this is more than the nitrogen pressure in our body, nitrogen enters our tissues and increases the nitrogen pressure there.
That is the advantage of breathing nitrox. If we breathe 32% nitrox on such a dive, the nitrogen partial pressure is 4 * 67 = 2.68, so we take on less nitrogen.
As we ascend, the total pressure drops, and the nitrogen partial pressure drops, too. When it is less than the pressure in our tissues, we begin to off-gas nitrogen from those tissues. Technical divers like to accelerate that by breathing stronger and stronger nitrox mixes to get the biggest possible difference between the nitrogen pressure in the body and the nitrogen pressure in the mix we are breathing.
At 20 feet, it is considered safe to breathe pure oxygen. When they do, there is no nitrogen in the mix, so the partial pressure of nitrogen is zero. With any air or nitrox mix, the shallower you are, the greater the pressure difference. Once you are no longer breathing any nitrogen, though, it doesn't matter any more. The nitrogen partial pressure in pure oxygen is zero at any depth.
No.
The partial pressure of N2 is zero when breathing pure oxygen - at any depth.
At a shallower depth the supersaturation of dissolved N2 is greater though. Hence it will exit faster.
If the depth is TOO SHALLOW then there will be bubbles, so optimization will be diffucult.
The ability of a liquid to hold dissolved gas at pressure X is relevant here! The higher the ambient pressure, the more gas in the liquid!
Yes. Zero.
To be more specific:
When you dive at a depth of X a certain amount of nitrogen will diffuse into your body.
When you ascend, that gas will ooze out.
The speed of off-gassing depends on depth change.
Shallower means faster.
When you dive at a depth of X a certain amount of nitrogen will diffuse into your body.
When you ascend, that gas will ooze out.
The speed of off-gassing depends on depth change.
Shallower means faster.
Since we're in Basic Scuba subforum, do you think that you could not get into deco and/or being on oxygen? Take that part of the convo over to Advanced subforum.
A very good point indeed!
mariosx
Contributor
For recreational dives up to 100', 30-45 seconds ascent to half of the maximum depth and stop for 30 seconds. Then ascent for 10' for 30 seconds and 30 second stop, repeatedly until I hit the surface.
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