question on physics

[Searcaigh]

Ok even though this is not possible due to air constraints and what not Its only hypothetical....

So what your saying is if this person were to survive long enough somehow for a person to get to them but it places him outside of scuba dive groups and NDLS on the accent he would have to make deco stops accordingly correct?

Absolutely, if the person survived long enough trapped and still breathing air at 66ft / 20M then they would have to go into deco after a certain period of time according to the tables.

 

[Garrobo]

I flunked physics.

 

[CAVDVR93538]

Also no expert, but that makes sense to me as well.[/QUOTE

The surface pressure is 1 atm or 14.7 psi, at 66 feet that is 2 atm plus the surface.
That makes 3 atm absolute with the windows closed and for purposes of the question, the car has sunk to 66 feet.
2 atm for the water pressure and the air inside, just like a scuba cylinder, plus 1 for the surface.
The NDL from the PADI tables is 66 feet for 40 minutes. Any longer than 40 minutes you now start a dive that will require decompression obligations.
Most recreational divers don't have the tools and training to plan a dive that requires decompression. Many will say, that is what my computer is for, but what about the gas. Do you have enough to complete decompression? That is what planning is all about. Plan the dive and gas concerns and not have it be a suprise when your computer says that you have 10 minutes (ex.) of deco and you only have 5 minutes of gas. SUPRISE a trip to the chamber, maybe! or worse!!

 

[ben_wilson3301]

Considering he was in a car under water I wouldn't worry about deco and get him to the surface at a controlled rate and then a hospital as Im sure he would be very shaken up

 

[fire_diver]

Just curious as to how this would work so I figured Id ask others who had more knowledge.

As we know our regulators deliver air to us based on the adjusted ambient pressure of depth. (I think) My question is simple. If a person was to do say a rescue dive where a person was trapped in an air pocket say in a car that had submerged. If this was at 2 atmospheres or 66 feet in depth. what would the result be if you were to come inside that air pocket and allow someone to use your alternate air and then come to the surface? .

If the car was at 66 feet, it would be at 3ata. The air bubble inside the car would also be at 3ata. There would be no difference between breathing from your reg or the air pocket.

Would it make a diffrence since they were in an air pocket all the way to the bottom as far as the capacity of the lungs are concerned? What would be any concerns on this application?.

No, the lungs would have the same capacity as on the surface, because the air source is still pressurized equal to the depth.

iF This seems like a stupid question I apologize in advance just something I was curious of.

No honest question is stupid.

 

[fire_diver]

disregard.

 

[DandyDon]

Absolutely, if the person survived long enough trapped and still breathing air at 66ft / 20M then they would have to go into deco after a certain period of time according to the tables.

In theory. In practice, not happening. Even if you tried that, the victim would bolt on breath old and embolize. If you ever were to find yourself in this situation, get them to the surface, then deal with N2 theory later at the hospital - where they will be evaluated on O2 anyway.

 

[TMHeimer]

We are assuming (and correctly, I think) that no car is air tight. If it were, then you'd be dealing with a non-flexible container--like a tank. The pressure in the tank is reduced to ambient via the reg. So the air in the car may take a little while to get to ambient pressure as it equalizes through little openings in the body. So if the rescuing diver broke the glass before equalizing was complete he would be possibly sucked in real quick?

 

[DandyDon]

We are assuming (and correctly, I think) that no car is air tight. If it were, then you'd be dealing with a non-flexible container--like a tank. The pressure in the tank is reduced to ambient via the reg. So the air in the car may take a little while to get to ambient pressure as it equalizes through little openings in the body. So if the rescuing diver broke the glass before equalizing was complete he would be possibly sucked in real quick?

Nah, water sucks in easier, but it'd be leaking pretty fast.

 

[al248005]

As soon as the diver broke the window or opened the door the little amount of air that was inside the car would escape and the car would be flooded with water completely.

Also, if the person was inside the car the whole time going I doubt they would have enough time to properly equalize and the other side is would they even think to equalize. Yes in here people would think of that but you say that to the normal person who doesn't dive they will look at you like what in the world are you even talking about.