Switching gasses at depth?

[cos]

.... why do I see tech divers with thousands of dives carrying long hoses? Presumably their dive buddies would never make such an amateur error, so is the long hose strictly for pushing your rig through constrictions?

And why do all the tech agencies from GUE to TDI to IANTD to the cave folks all put so much emphasis on practicing the OOG and air sharing drills, even for divers carrying manifolded doubles? One would think that by the time someone is taking GUE Tech 1 they plan their dives such that even if they never look at their gauge they are in zero danger of running out of air. So what's up with the long hose drills??

If I'm diving backmount I won't remove my kit to get through a restriction, sidemount is another story.

There are many theories about the long hose deployment and gas sharing drills. If I know that you know how to donate gas and we have practised this before the dive I feel better about you as a buddy and am a little more confident with you and hopefully you with me.

In the event of a real emergency at depth and I signal an emergency, shut down the post/isolator and you donate your long hose to me, I know that you have enough gas in your tanks for both of us (dive/gas planning) so now I'm not so freaked out. I also know that you are a good and competent buddy and can take charge of the situation. Further, I have protected what remains of my gas which now acts as an even greater safety buffer if there are any issues on exit/surfacing - which is why I won't take off my kit to pass through a restriction diving backmount.

As far and Tech 1 or any competent divers never having to look at their gauges that is not true. All divers need to look at their gagues and monitor their gas - there should just be no surprises. Sometimes there are and they are usually caused by me as I left my brain on the boat/shore which is why my buddy is there and hopefully his brain is functioning better than mine.

And by the way, manifolded doubles is not the answer to OOG situations. If that manifold is is sheared off exposing the gas in both tanks you are really ********D and you better hope to hell you buddy remembers that S-drill.

 

[Reg Braithwaite]

manifolded doubles is not the answer to OOG situations. If that manifold is is sheared off exposing the gas in both tanks you are really ********D and you better hope to hell you buddy remembers that S-drill.

So the folks diving independent doubles tell me!

 

[cos]

....And likewise while none of them are going to jump into a high-commitment overhead dive with a single tank, many of them dive a single AL-80 without a pony when vacationing. What's up with that?

Dive planning: carry enough gas for you and your buddy to manage the crisis and get safely to the surface. It's really not that confusing.

 

[Reg Braithwaite]

Dive planning: carry enough gas for you and your buddy to manage the crisis and get safely to the surface.

Whoa.

Do you agree that for some dives it is not ridiculous to deliberately plan and execute a dive where you rely on your buddy to carry enough gas for the two of you to manage a crisis and get safely to the surface?

 

[cos]

Whoa.

Do you agree that for some dives it is not ridiculous to deliberately plan and execute a dive where you rely on your buddy to carry enough gas for the two of you to manage a crisis and get safely to the surface?

If I'm diving a single tank (single valve) I am way more reliant on my buddy for gas sharing. Every dive that I do I have at least enough gas to manage a crisis and get us to the surface safely. If my buddy is not doing the same I'm bubble watching with the captain or more likely throwing up over the railing. I'm very prone to seasickness.

 

[Rick Inman]

If I'm diving backmount I won't remove my kit to get through a restriction, sidemount is another story.

Hey Cos, I'm enjoying reading your posts. How about filling out your dive profile some, so we can know your training and experiencs?

 

[Reg Braithwaite]

If I'm diving a single tank (single valve) I am way more reliant on my buddy for gas sharing. Every dive that I do I have at least enough gas to manage a crisis and get us to the surface safely. If my buddy is not doing the same I'm bubble watching with the captain.

Ok, so what I am taking away from this is that under some circumstances you consider it reasonable to dive with a single tank and a single valve and rely on your buddy for gas sharing.

Works for me.

 

[cos]

Ok, so what I am taking away from this is that under some circumstances you consider it reasonable to dive with a single tank and a single valve and rely on your buddy for gas sharing.

Works for me.

No. Thats not really what I'm saying.

I'm not really relying on my buddy - here's a hypothetical scenario that hasn't been actually calculated but illustrates what I'm thinking:

I have 3000psi in my single al80 with 1 valve. It will take 300psi to get me safely to the surface so I need an additional 300 to get my buddy up. I figure I'll need another 200psi to manage a situation at depth which means that my absolute turn pressure is 800psi to get us both up to the surface with 0psi left. Planning to arrive on the boat/surface with 0psi is not cool and I like to add a couple of hundred psi for safety so lets say I'll turn at 1000psi. If at the maximum dive time/psi used of 2000psi I have a failure at the 1st stage or forward I can feather the valve and get myself to the surface with probably enough gas to arrive safely. If the failure is behind the 1st stage (tank O-ring or burst disk) that's another story but I will still have some gas. I'll signal my buddy, let him know the situation and know that he has enough gas to get us both to the surface safely. I'll probably keep breathing my tank until its really low or empty - as it will be spilling gas anyway and keep in close (touch) contact with my buddy as we ascend. Obviously signal when I"m out and he will donate.

Am I relying on my buddy for gas sharing? Not really since the likelyhood of a tank O-ring or burst disk failure at the end of a dive is really unlikely as the tank pressures are so much lower and I probably have enough gas to get myself to the surface safely in the event of a 1st stage & forward failure.

This is one major issue with single tank single valve diving and it scares the **** out of me sometimes. Add to this the fact that many recreational divers are deep, in drysuits, doing minor penetrations, limited visibility, and in current there is very little or no room for any failures.

 

[Reg Braithwaite]

No. Thats not really what I'm saying.

I'm not really relying on my buddy ... the likelyhood of a tank O-ring or burst disk failure at the end of a dive is really unlikely as the tank pressures are so much lower and I probably have enough gas to get myself to the surface safely in the event of a 1st stage & forward failure.

This is one major issue with single tank single valve diving and it scares the **** out of me sometimes. Add to this the fact that many recreational divers are deep, in drysuits, doing minor penetrations, limited visibility, and in current there is very little or no room for any failures.

So help me understand: Why do experienced divers carry long hoses and why do tech agencies emphasize gas sharing practice? You suggested earlier it had to do with being comfortable with your buddy's skills. This makes sense if you are insta-buddying, but most people I know frown on insta-buddies and dive with people they know very, very well. They don't need to do an S Drill together to be confident in each other.

And in addition to carrying a long hose, many serious divers avoid placing deco bottles on their RHS to keep the long hose free. This seems like an awful lot of bother if donating gas is just an optional nice-to-have with no real necessity for a diver to rely on their team for gas.

And further, if it is just a temporary breathe off it while sorting out the issues, why make it a long hose? The long hose is presumably so that both divers can share gas all the way home or all the way to where they can switch to deco gasses or pick up bottles left in the cave.

Just a n00b asking questions here... But all this emphasis on the long hose and air sharing amongst some very experienced divers makes me think that there are people who place a certain amount of their trust in their buddies for more than just a nice-to-have comfort factor.

That may not be you, of course.

Update: This is really tiresome, I am unsubscribing. Self-rescue, great. Redundant gear, great. Treating every dive as a solo dive with your erstwhile buddy on the other side of the reef, great if it works for you and your buddy. To each their own. For those who think relying on a buddy in any fashion for anything is ridiculous, again great if it works for you and your buddy. Good night.

 

[Brewone0to]

Is the most important lesson of all.

What you wouldn't trust me with your life???
Come on now............You can trust me.......can't you?
Think about it............
Trust Me......

This thread can now continue.....