Why scuba diver can't share gas with freediver?

[Crush]

If he flashes you a cert card and does the OOA signal then he is likely also a scuba diver and will know to ascend while exhaling. Simple!

Oh yeah - if you are at 100 ft make sure that the free diver's scuba cert card is AOW and not just OW.

 

[redacted]

If he flashes you a cert card and does the OOA signal then he is likely also a scuba diver and will know to ascend while exhaling. Simple!

Sorry, wrong card. I was diving EAN.

 

[Dsix36]

I can not give a reason or even any definite answers BUT;

I was recently a deep safety diver (260') for a freediving competition. I was on my rebreather and waiting at depth to offer aid in the unlikely scenario that their other backup plan should happen to fail. I was given specific instructions to keep away from the diver until such time as they passed out, then I was to send them on a ride to the surface via a lift bag. The reasoning was two fold. there would be no way for the freediver to get any air from me and there was no way for the freediver to endanger me from panic.

We joked a bit about the safety statics and how a safety diver on a rebreather had a higher probability of death than the freediver. did

 

[mrdre]

Let's assume for the sake of argument that the freediver will not hold his/her breath and will stay with the scuba diver. So let eliminate that.

---------- Post added October 24th, 2014 at 12:57 PM ----------

I can not give a reason or even any definite answers BUT;

I was recently a deep safety diver (260') for a freediving competition. I was on my rebreather and waiting at depth to offer aid in the unlikely scenario that their other backup plan should happen to fail. I was given specific instructions to keep away from the diver until such time as they passed out, then I was to send them on a ride to the surface via a lift bag. The reasoning was two fold. there would be no way for the freediver to get any air from me and there was no way for the freediver to endanger me from panic.

We joked a bit about the safety statics and how a safety diver on a rebreather had a higher probability of death than the freediver. did

So you were given specific instructions NOT to share air, right?

 

[TMHeimer]

The big worry is of course that the free diver (or snorkeler, and I've been told this happens) just shows up at depth and wants the diver's air. If it was planned ahead of time and the free diver knows to keep his airway open if he ascends alone there shouldn't be a problem--just like a diver's CESA. A CESA from 100' COULD be a problem....

 

[Scott]

There is no problem if they both ascend sharing gas.

Unless the freediver somehow becomes separated from the regulator and is now doing an unassisted ascent.

 

[sea_ledford]

Assuming that, as everyone else has said, that the freediver knows about lung expansion injuries and breathes with you on the way up from 100' just as an out of gas diver would, it would be fine. However from 200' it would not work. I'm not sure the specific depth it happens at (probably depends on lung volume), but as a freediver descends their lungs keep compressing with depth until they are about the size of a fist and contain no gas, but instead are filled with fluid (blood plasma? Surfactant? I can't remember). At that point the freediver couldn't inhale even if they had gas available because their lungs are effectively collapsed, and they would not be able to inhale. Deep safety divers are generally just there to get the body back to the surface, so it can hopefully be revived.

I can't find the answer. The scenario is: the SCUBA diver is at 100 fsw, the free diver descends to 100 fsw, SCUBA diver shares the gas with the free diver, they both ascend sharing the gas.

What can go wrong with this? It seems that there is an opinion that this can kill the freediver, but I can't find any clear answer why and can't think of any reason why this is dangerous for the freediver. If it can be done from 100 fsw with air, can the same be done from 200 fsw with SCUBA diver using trimix?

 

[Aquavelvet]

Then there is this little problem called buoyancy control. Most free divers only become neutrality buoyant at some depth well below the surface. So even if they know how to keep their airway open durning an ascent on compressed gas, you will both end up on a free ride to the surface once they become positive.

Not a good plan for a happy ending, there are too many things that can go wrong, resulting in two victims.


Sent from my iPhone using Tapatalk

 

[CT Sean]

So if a freediver is at 30 meters and his lungs have compressed down to 25% of their normal size, maybe I'm wrong but it doesn't seem like it would be a good idea to suddenly inflate them by taking a breath off of scuba. But I'm willing to learn otherwise. Watch this cool video. I asked Walid about being offered air during the video and he told me that it could have seriously injured him if he had accepted the air. I didn't question him further about why. Walid is a world class freediver..

Freedive Roatan - El Aguila - YouTube

Anyway, it's a cool video. Enjoy!

I don't see how this is any different that diving to 30m on scuba and mostly exhaling. In both cases you've got lungs 25% filled with 4 atm of air. No offense, but being a world class freediver doesn't give someone a world class understanding of the physics of pressure (for the record I am neither a world class freediver nor have a world class understanding of the physics of pressure - but I do have a decent one).

 

[Pinecube]

Just for the record; I would never assume a snorkler/freediver knows to exhale after taking a breath off SCUBA at depth.