Request for comments on article - mixed OC / CCR teams

[doctormike]

DoctorMike,
I enjoyed the article as someone who occasionally dives mixed team. Diving wrecks in the Great Lakes I often worry more about other people who are on the boat and making sure they understand where my alternate is they run out of gas. I have visions of someone grabbing my loop then needing to buddy share from my bailout to the surface. Since buddy sharing isn't a skill that isn't often taught I'm sure it wouldn't be pretty. These are all worries on dive within the recreational limit.

As a Poseidon diver (I know, I'm going to die with so few O2 sensors) one thing to note is that many of the units don't have MAV's and training has a strong mantra of when it doubt bail out. For those units the best you could do for someone is to switch the BOV to open circuit.

Thanks! Yeah, I try not to be too specific about CCR design, since there are SO many variations...

I don't know much about Poseidons, can you tell me a bit more about that? Are you saying that there is no way of adding dil manually, or just no separate MAV button? I have the International JJ, which doesn't have a dil MAV per se, but there is the button on the ADV, which is effectively a MAV and I tell OC divers about it. I just want the OC diver to know how to safely put fresh gas in the loop.

I know that a buddy of mine with an older KISS would do that by switching the BOV, inhaling bailout, and then exhaling it into the loop. Is that what you mean? That the BOV is the way to add dil to the loop?

I guess the most important take home message is that the OC diver needs to listen to the CCR diver about the specifics of the unit. Can't really cover all possibilities in an article!

 

[Gareth J]

Thanks! Yeah, I try not to be too specific about CCR design, since there are SO many variations...

I don't know much about Poseidons, can you tell me a bit more about that? Are you saying that there is no way of adding dil manually, or just no separate MAV button? I have the International JJ, which doesn't have a dil MAV per se, but there is the button on the ADV, which is effectively a MAV and I tell OC divers about it. I just want the OC diver to know how to safely put fresh gas in the loop.

I know that a buddy of mine with an older KISS would do that by switching the BOV, inhaling bailout, and then exhaling it into the loop. Is that what you mean? That the BOV is the way to add dil to the loop?

I guess the most important take home message is that the OC diver needs to listen to the CCR diver about the specifics of the unit. Can't really cover all possibilities in an article!

This highlights a point I make when I teach the BSAC lesson on rebreathers to OC divers.

If you are presented with OC kit from another manufacturer, like a regulator or BC, it is highly unlikely that it will be so unfamiliar that you can't operate it. With CCR's the variation between manufacturers and their philosophy is considerable. So even a CCR diver may be flummoxed by another CCR divers unit.

 

[doctormike]

This highlights a point I make when I teach the BSAC lesson on rebreathers to OC divers.

If you are presented with OC kit from another manufacturer, like a regulator or BC, it is highly unlikely that it will be so unfamiliar that you can't operate it. With CCR's the variation between manufacturers and their philosophy is considerable. So even a CCR diver may be flummoxed by another CCR divers unit.

Exactly. That's why you don't need a crossover class when you switch from ScubaPro to Atomic regulators!

 

[wnissen]

OK, new question!

Our underwater photography club just had a great zoom session with Peter Symes, the editor-in-chief of X-Ray magazine. One of the things that I took home from the talk was that opening with an anecdote sometimes grabs the readers attention. What do you guys think about adding this to the opening of the text, assuming that I'm going to submit this for publication?


Bill and Tony had been dive buddies for several years, frequently visiting the local wrecks near their shore town. Tony had been content doing single tank recreational dives, but Bill had gotten into technical diving and had recently certified on a closed circuit rebreather. Given their longstanding friendship and the lack of other local rebreather divers, Bill had continued to dive with Tony, visiting the same wrecks and adjusting the dive plan so that Tony would never get close to his gas or decompression limits.

At 90 feet, about 10 minuets into their first dive on beautiful morning with spectacular conditions, Tony tried to get Bill’s attention and couldn’t. Bill was staring right at Tony. He seemed to be breathing normally, but he didn’t respond to hand signals. Tony reached out and grabbed Bill’s shoulder, and he still didn’t respond.

I really like scenario-based articles, this is an excellent start.

 

[doctormike]

I really like scenario-based articles, this is an excellent start.

So what do you think? Finish the article with this?

Tony realized that Bill was conscious and breathing but unresponsive. He remembered how Bill had gone over this possibility in their pre-dive discussions, and he knew just what to do. While he wasn't sure what exactly was wrong with the gas in the loop, he knew that Bill needed fresh gas of a known and safe mix right away. Holding the loop firmly in place, he switched the bailout valve and bubbles started flowing from the vent. Bill soon began to respond to hand signals, and they made a safe ascent together. On the surface, it became apparent that the CCR solenoid had failed, and that Bill hadn't noticed the dropping PPO2 levels.

 

[KenGordon]

Really Bill ought to have been more careful to avoid whatever issue killed him. By getting in the water with an OC diver without training to support an unconscious CCR diver he accepted extra risk, in the style of a solo diver plus a bit.

Honestly, the best advice for an OC diver with a CCR buddy is to avoid being a distraction and not change depth too fast. Absolutely the biggest risk I take is being distracted looking after some OC diver and failing to know my ppO2 or failing to do all the steps needed to set up the machine in the first place.

Does anyone know a case of a non CCR trained OC diver successfully (ie alive a week later) lifting an unconscious CCR diver or even recovering the loop ppO2? Or even of a case where a CCR diver needed rescuing by an OC diver?

 

[crcobb]

DoctorMike,
You can add dilutant to the loop by pressing the purge button on the BOV on the Poseidon. The purge releases lots of air so not sure I'd ask someone to press that button. If you don't have a good grip on the mouth piece it might blow it right out of your mouth. For my unit I'd ask someone to switch the unit to OC.

 

[doctormike]

Really Bill ought to have been more careful to avoid whatever issue killed him.

Right, but it's not an article about how do dive a rebreather safely. This is Tony's article, someone else can write one for Bill!

By getting in the water with an OC diver without training to support an unconscious CCR diver he accepted extra risk, in the style of a solo diver plus a bit.

Right, but that's the point, to help the OC diver know what to do in this situation. I mean, it's fine if you think that this should never happen, that mixed teams are just a bad idea and I shouldn't encourage them. That's not an unreasonable point, since currently, the only way to be formally trained in rescuing a CCR diver is to do CCR training. But I think that there are a lot of teams like this, whether or not the training agencies formally address the issue, and it's probably better to give the OC diver SOME idea of what to do...

 

[doctormike]

DoctorMike,
You can add dilutant to the loop by pressing the purge button on the BOV on the Poseidon. The purge releases lots of air so not sure I'd ask someone to press that button. If you don't have a good grip on the mouth piece it might blow it right out of your mouth. For my unit I'd ask someone to switch the unit to OC.

Got it. So the BOV is an integral part of the design, and it can't work with a DSV. That makes sense.

 

[KenGordon]

Right, but it's not an article about how do dive a rebreather safely. This is Tony's article, someone else can write one for Bill!



Right, but that's the point, to help the OC diver know what to do in this situation. I mean, it's fine if you think that this should never happen, that mixed teams are just a bad idea and I shouldn't encourage them. That's not an unreasonable point, since currently, the only way to be formally trained in rescuing a CCR diver is to do CCR training. But I think that there are a lot of teams like this, whether or not the training agencies formally address the issue, and it's probably better to give the OC diver SOME idea of what to do...

I dive in mixed teams almost all the time. I just don’t think they will be able to rescue me. Personally, even knowing exactly what is supposed to happen, I find it very difficult. It might be marginally easier for an OC diver to perform the rescue as they’d not have their own counterlungs to worry about, and in warm water without drysuits it would be a bit easier, but without having ever practiced it I am very sceptical.