Gas sharing at deco stops

[PfcAJ]

And when you run out of deco gas you have nothing to breath until you fiddle with plugging in one of your sidemount tanks.

Having 2 different gases plugged in is farm animal stupid and I can't imagine that you're doing that.

Please don't surprise me.

 

[Patoux01]

Having 2 different gases plugged in is farm animal stupid

Hey hey hey. Stop that. Pigs are intelligent animals.

 

[Dan_P]

I don't understand this. How do you have more backgas in sidemount if your gas planning is the same?

It's a good question.
I dive the Z system, where your deco gas plugs in and feeds the entire system, both longhose and necklace. That means I can donate my deco gas the same way as I always do, and both I and my OOG buddy are breathing the deco gas at the same time.
Therefore, we don't have to stay longer at the deeper stops and take turns breathing the deco gas, which will save me backgas.

And when you run out of deco gas you have nothing to breath until you fiddle with plugging in one of your sidemount tanks.

Having 2 different gases plugged in is farm animal stupid and I can't imagine that you're doing that.

Please don't surprise me.

I'm usually not caught by surprise by my gas running low.
In my view, the whole idea of awareness transcends into both the decompression schedule and gas management, so it is fair to start preparing when the little needle gets close to the "0".
If this was any legitimate problem, it would be one in much larger scale than any one system.
Would you care to refer to any particular safety statistics that might support your claims?

One might choose to keep the bottom gas plugged in, if one so chooses - speaking of awareness, do you often incur undetected roll-off's/roll-on's in sidemount on your deco hangs?

But maybe, in terms of both scope and scale, the issue of maximal gas density would be a more suitable topic to dwell on, if we were to make conversational contributions that might actually leave a positive impact.

Or, if you wish to refrain, for the sake of fairness, you could tell how you solve the case at hand, and show why that is superior.

 

[PfcAJ]

It's a good question.
I dive the Z system, where your deco gas plugs in and feeds the entire system, both longhose and necklace. That means I can donate my deco gas the same way as I always do, and both I and my OOG buddy are breathing the deco gas at the same time.
Therefore, we don't have to stay longer at the deeper stops and take turns breathing the deco gas, which will save me backgas.



I'm usually not caught by surprise by my gas running low.
In my view, the whole idea of awareness transcends into both the decompression schedule and gas management, so it is fair to start preparing when the little needle gets close to the "0".
If this was any legitimate problem, it would be one in much larger scale than any one system.
Would you care to refer to any particular safety statistics that might support your claims?

One might choose to keep the bottom gas plugged in, if one so chooses - speaking of awareness, do you often incur undetected roll-off's/roll-on's in sidemount on your deco hangs?

But maybe, in terms of both scope and scale, the issue of maximal gas density would be a more suitable topic to dwell on, if we were to make conversational contributions that might actually leave a positive impact.

Or, if you wish to refrain, for the sake of fairness, you could tell how you solve the case at hand, and show why that is superior.

I understand how it works. And I think it's bad. When you plug in 50% and then give the Long hose to your buddy you're in for a treat if the qc6 comes unplugged. You have nothing immediate to breath and have to fiddle with tanks and qc6s to get something running.

Im glad you aren't usually surprised by being low on gas. However you also aren't usually sharing gas from one source and dealing with the complication (big or small) that comes with it. It's one more layer of stuff to deal with that's not necessary.

There's no statistics for any of this. You know that.

Having two gases plugged in is a recipe for problems. It's super easy to bump a bottle and have it I turn on (and with two gases plugged in now you don't know what you're breathing) and a lot of times deco isn't just hanging mid water. It's moving through cave, sometimes restrictive cave.

Real life stuff.

So much of UTDs nonsense is based on fantasy ideal situations, like that silly pocket reg baloney. Ugh.

 

[Dan_P]

Real life stuff.
So much of UTDs nonsense is based on fantasy ideal situations, like that silly pocket reg baloney. Ugh.

Wow. Spare 2.-stages is a thing of the time before the isolatable manifold (when there was only a distribution block). One can bring them if one wants, of course, but they're not in the standards.
Your bashing literally comes from some old video you found on youtube.

And I've heard a lot, but never did I meet anyone who seriously ventured the notion that UTDs diving magically fell out of the sky.
It's fair game if you don't like something. If you don't like sidemount, don't dive sidemount. If you don't like manifolds, don't dive with manifolds. If you want an eCCR, go ahead and do that then. I'm not the scuba police, and more importantly, neither are you, sir.

I've answered the OPs question primarily on gas density, and secondarily on how I approach things in the various configurations that I use (without even mentioning the Z system specifically).
Your injection of yourself with such vigor and so little but outdated youtube videos to support you, such gall aimed at UTD and so little of you explaining how you solve things, looks to me - being quite honest - out of place.

There's no statistics for any of this. You know that.

I know damn well UTD has had zero fatalities across every domain, on every system including sidemount and rebreather, in nearly a decade running.
Considering the level to which the bollocks-artistry of scuba have been bandying around their gall-infested warnings, bashings and selfrighteous opinions about the organization, I'd say the constrast is stark at least.

I understand how it works. And I think it's bad. When you plug in 50% and then give the Long hose to your buddy you're in for a treat if the qc6 comes unplugged. You have nothing immediate to breath and have to fiddle with tanks and qc6s to get something running.

Im glad you aren't usually surprised by being low on gas. However you also aren't usually sharing gas from one source and dealing with the complication (big or small) that comes with it. It's one more layer of stuff to deal with that's not necessary.

If this were a genuine point, it would be valid for a host of rebreathers as well. It's not.
I'm glad however, that your language is now taking a form more appropriate in indicating you're talking about your personal preference rather than ultimative truths.

That's not saying that I agree with what you're saying, of course.

Having two gases plugged in is a recipe for problems. It's super easy to bump a bottle and have it I turn on (and with two gases plugged in now you don't know what you're breathing) and a lot of times deco isn't just hanging mid water. It's moving through cave, sometimes restrictive cave.

If one is constantly bumping off and on valves without noticing, and never does flow checks, do consider at least that the roll-off scenario is of similar impact in Z and backmounted doubles.
The cut-off argument is no different than it would be if one were diving a rebreather, say, the RB80.
I don't think there's anything on it, to be fair.

 

[Michael Guerrero]

As others said above, if you're breathing the same gas as already planned then I don't see a reason off-gassing would be different. However, CO2 retention would be an issue. If you can't remain calm during this type of deco, then I'd expect higher CO2 levels, which accelerate breathing and I think increases risk of oxtox. Outside of that, inspired gas doesn't change from the plan so...

 

[boulderjohn]

However, CO2 retention would be an issue. If you can't remain calm during this type of deco, then I'd expect higher CO2 levels, which accelerate breathing and I think increases risk of oxtox. Outside of that, inspired gas doesn't change from the plan so...

During one of my earlier training dives for tech diving, we began the training dive with doubles with back gas, a stage bottle and two deco bottles. One by one, we lost pretty much everything. The instructor put both of us out of gas on both our back gas and stage bottles, leaving us nothing but our deco bottles. We had to do a number of simulated deco stops. Then he indicated that my buddy's deco gas was "broken," meaning we had no choice but to buddy breathe my deco gas for the remaining deco stops. Not thinking that was difficult enough, the isntructor took my mask and my backup mask and my buddy's backup mask. That means we had to buddy breathe while holding deco stops while I was blind.

I had to keep one hand on the knot in the ascent line so I knew my depth and where everyone was. I had to manipulate my dry suit exhaust and my wing exhaust to hold depth. I had to wait for the feel of the regulator being put back on my lips when it was my turn to breathe, and I had to give the regulator back into space when I was done with my second breath. I had to exhale, of course, the entire time I did not have a regulator, but since this is something we don't regularly practice, and since I could not see what was going on (like if my buddy was still there), I exhaled a bit too slowly. When we were finally done, my CO2 buildup was enormous. When I got to the surface, my breathing rate was simply HUGE as I tried to get rid of all that unwanted bad gas. It was something you do not want to experience.

I do not ever want to go through that again, and I am very thankful that the scenario of that dive is as about as close to impossible as you will ever experience on a training dive.

 

[kensuf]

Wow, interesting story. Where does the line between simulating realistic failure scenarios and hazing get drawn?