Flying After Diving
- Thread starter PK1
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
You're confusing the fraction of the components with the partial pressure. Fractions will never exceed 100%, and it is the latter which drives absorption into your tissues. The gas being inhaled is 78% nitrogen at all depths. The partial pressure is 0.78 atm (surface) or 1.13 atm (15 ft).
Partial Pressure = Fraction x Ambient (total) Pressure
This is one of the main things taught in a nitrox class. Hope it helps!
kdlv
Registered
I didn't realize the swimming pool was at altitude.
Let's simplify it and pretend we are at sea level with 1 atm surface and 1.5 atmospheric pressure at depth of 5m/15ft in salt water that affects the partial pressure of nitrogen and oxygen in the mix.
Fractions never exceed 100%, of course.
The gases are subject to the 1.5 bar pressure at depth of 5m and that translates to their partial pressure. Dalton law of partial pressure states that total pressure of mix is the sum of each component partial pressure, so fractions of O2 and N2 are individually multiplied.
If the tank was with you at this depth, then the tank would be subject to same 1.5bar pressure at depth. However the gas mixture in it, being pressurized to 50-300 bar would be isolated from ambient pressure (or would be marginally impacted) until it passes through the orifice of the 2nd stage and is now subject to ambient pressure.
So if I understand correct, it really doesn't matter where the air is coming from in this scenario (hookah vs pressurized tank at your depth), in both cases Dalton law principles apply to the gases and their partial pressure in the mix. Is that correct?
And yes, the Nitrox course covers most aspects, but not such scenarios, or at least I haven't found it in the materials.
A Greek lady once told me "to 'assume' means to make an a$$ of you and me!", so i prefer to ask
Let's simplify it and pretend we are at sea level with 1 atm surface and 1.5 atmospheric pressure at depth of 5m/15ft in salt water that affects the partial pressure of nitrogen and oxygen in the mix.
Fractions never exceed 100%, of course.
The gases are subject to the 1.5 bar pressure at depth of 5m and that translates to their partial pressure. Dalton law of partial pressure states that total pressure of mix is the sum of each component partial pressure, so fractions of O2 and N2 are individually multiplied.
If the tank was with you at this depth, then the tank would be subject to same 1.5bar pressure at depth. However the gas mixture in it, being pressurized to 50-300 bar would be isolated from ambient pressure (or would be marginally impacted) until it passes through the orifice of the 2nd stage and is now subject to ambient pressure.
So if I understand correct, it really doesn't matter where the air is coming from in this scenario (hookah vs pressurized tank at your depth), in both cases Dalton law principles apply to the gases and their partial pressure in the mix. Is that correct?
And yes, the Nitrox course covers most aspects, but not such scenarios, or at least I haven't found it in the materials.
A Greek lady once told me "to 'assume' means to make an a$$ of you and me!", so i prefer to ask
halocline
Contributor
The simplest way of looking at it is that breathing must be at the ambient pressure of your lungs. Breathing is essentially the act of equalizing pressure between the lungs and the area surrounding your body. So if you are at 1.5 atm, you will be breathing gas pressurized to 1.5 atm. It makes no difference whether that gas is from a tank or a compressed surface supply. Air at 1.5 atm has 1.5 times as many molecules of N2 and 1.5 times as molecules of O2 as the same volume of air on the surface. That’s where the increase in partial pressure comes from.I didn't realize the swimming pool was at altitude.
Let's simplify it and pretend we are at sea level with 1 atm surface and 1.5 atmospheric pressure at depth of 5m/15ft in salt water that affects the partial pressure of nitrogen and oxygen in the mix.
Fractions never exceed 100%, of course.
The gases are subject to the 1.5 bar pressure at depth of 5m and that translates to their partial pressure. Dalton law of partial pressure states that total pressure of mix is the sum of each component partial pressure, so fractions of O2 and N2 are individually multiplied.
If the tank was with you at this depth, then the tank would be subject to same 1.5bar pressure at depth. However the gas mixture in it, being pressurized to 50-300 bar would be isolated from ambient pressure (or would be marginally impacted) until it passes through the orifice of the 2nd stage and is now subject to ambient pressure.
So if I understand correct, it really doesn't matter where the air is coming from in this scenario (hookah vs pressurized tank at your depth), in both cases Dalton law principles apply to the gases and their partial pressure in the mix. Is that correct?
And yes, the Nitrox course covers most aspects, but not such scenarios, or at least I haven't found it in the materials.
A Greek lady once told me "to 'assume' means to make an a$$ of you and me!", so i prefer to ask
Seems like lots of folks are overanalyzing this (imho). I’d guess that you likely have 12 hours after you complete your dive to before you fly? If so, you are good against the widely accepted DAN guidance:
Guidelines for Flying After Diving
The recommendations for flying after diving come from a DAN study — read all about the study workshop and conclusions.
dan.org
Similar threads
