Rebreathers ?

[BillGraham]

This is a different discussion. I agree that I don't "need" the rebreather for most of my dives. If I'm down cave diving and everyone else is diving open circuit, I just go with the oc sidemount rig because it's simpler. I figure, why should I complicate things with the CCR? If I'm diving with another CCR diver, or a top gun open circuit diver with the sac rate of a hamster (Edd?) I'll dive the rebreather. Otherwise, I don't want to subject the rest of the team to watching me gear up for an extra 5-10 minutes and having to think about the complications of my rig if I were to have a problem.

[gianaameri]

This is a different discussion. I agree that I don't "need" the rebreather for most of my dives. If I'm down cave diving and everyone else is diving open circuit, I just go with the oc sidemount rig because it's simpler. I figure, why should I complicate things with the CCR? If I'm diving with another CCR diver, or a top gun open circuit diver with the sac rate of a hamster (Edd?) I'll dive the rebreather. Otherwise, I don't want to subject the rest of the team to watching me gear up for an extra 5-10 minutes and having to think about the complications of my rig if I were to have a problem.

I dive Solo, so I do not have to worry about the "team" or tailor my dive/configuration to other diver's needs/wants/requirements.

I use the rebreather because given the same amount of gas I carry vs OC, it gives me a greater safety margin (of course I could do a longer penetration than OC).

Plus, I stay warmer, and that makes me more comfortable and safer (and I can dive longer if I want to).

Also, I have very little problems with percolation, and can dive for a week in the same cave without disturbing it (OC for a couple of days and the vis. is gone due to percolation, and if more than one diver goes in OC the vis. is gone in a single dive; you exit no vis. when a DIR team goes in where I dive).

And in an emergency (i.e. lost ), I have 11 hours on the rebreather (in emergency), plus a couple of hours more on the bail-out gas (not very nice as after 6 hours of being "lost" I presume I'll have tears going down my eyes like a little child and will be praying like the Pope).

So, there are clear advantages to use a rebreather in a cave on most dives, but it does kill, although not always.

[BillGraham]

I dive Solo, so I do not have to worry about the "team" or tailor my dive/configuration to other diver's needs/wants/requirements.

I use the rebreather because given the same amount of gas I carry vs OC, it gives me a greater safety margin (of course I could do a longer penetration than OC).

Plus, I stay warmer, and that makes me more comfortable and safer (and I can dive longer if I want to).

Also, I have very little problems with percolation, and can dive for a week in the same cave without disturbing it (OC for a couple of days and the vis. is gone due to percolation, and if more than one diver goes in OC the vis. is gone in a single dive; you exit no vis. when a DIR team goes in where I dive).

And in an emergency (i.e. lost ), I have 11 hours on the rebreather (in emergency), plus a couple of hours more on the bail-out gas (not very nice as after 6 hours of being "lost" I presume I'll have tears going down my eyes like a little child and will be praying like the Pope).

So, there are clear advantages to use a rebreather in a cave on most dives, but it does kill, although not always.

I agree with everything you say here. For diving solo (which I don't generally do in caves), it absolutely makes more sense. Don't get me wrong, I love my rebreather, I just usually don't dive it in situations where I can easily do the dive on OC, and the rest of the team is diving that way.

[gianaameri]

I agree with everything you say here. For diving solo (which I don't generally do in caves), it absolutely makes more sense. Don't get me wrong, I love my rebreather, I just usually don't dive it in situations where I can easily do the dive on OC, and the rest of the team is diving that way.

Understandable. Mixed dive teams are a recipe for disaster (although it can be done, personal choice at the end).

[BillGraham]

It's not a recipe for disaster in the normal situation at all. Let's say I'm diving with an OC sidemount diver, and we are doing a "normal" 100 minute dive at 100 feet or so. I have an Al 80 dil bottle with a 7 foot hose on it, and an aluminum 80 stage if we are going anywhere. If the OC diver loses half his gas, he's got enough to get out, and I've got another 160 cubic feet or so for him. If I have to go off the loop, I've got the 160 cubic feet and my buddy has enough to get me out without it, depending on my sac rate. For extended range dives, I can see your point completely.

[Bobby]

I have not had a single piece of electronics for use on rebreathers work properly (other than from one company), and yet the safe use of rebreather requires at minimum to know the pPO2, which requires electronics, as we cannot know pPO2 otherwise.

You add to that the propensity for human errors and complacency (all divers make mistakes and you will find at least one human error in every fatality and in every dive in general), the odds are you will die on rebreather sooner or later.

Am I the only one to have experienced rebreather related electronics which do not work reliably and are subject to a number of intermittent faults?

I have had electronic issues and failures with every CCR I have owned. Putting it in perspective though I have had OC failures as well. When the type of diving I do and the amount of dives are considered I would say that my present CCR's electronics are very reliable. The same as my OC gear requires maintenance and from time to time even with maintenance there are failures, the CCR gear also has them. Compared to other units I have had my present one is by far the most reliable and will tolerate considerable abuse.

When it comes to dives of depth, duration, or both that require CCR or multiple stages and set up dives there are going to be equipment failures if you do enough of them. The CCR can save considerable set up time, has added benefits (variable controlled PO2, moist warm breathing, etc.), and can add a dimension of safety with gas planning.

[gianaameri]

It's not a recipe for disaster in the normal situation at all. Let's say I'm diving with an OC sidemount diver, and we are doing a "normal" 100 minute dive at 100 feet or so. I have an Al 80 dil bottle with a 7 foot hose on it, and an aluminum 80 stage if we are going anywhere. If the OC diver loses half his gas, he's got enough to get out, and I've got another 160 cubic feet or so for him. If I have to go off the loop, I've got the 160 cubic feet and my buddy has enough to get me out without it, depending on my sac rate. For extended range dives, I can see your point completely.

What if there is a restriction and on the way out visibility is nil and the sidemount diver goes through and the rebreather diver cannot go through?

That is the near fatality we had not too long ago (it would have been the first and only one where we dive). Two RB80 DIR divers could not make it back out past the restriction due to nil visibility (and yes of course the line could have been run a little better in hindsight, but it was not), while the sidemount diver made it out (because he was leading). After he passed the restriction, in his opinion he could not wait any longer than he did or provide assistance and he exited and called in the rescue team.

Had the sidemount diver not gone through first, he would have been stuck behind the RB80 divers and the outcome would have been very different.

When I said it is a recipe for disaster it is because I have in mind the environment where I dive. However, if the environment is different and more benign, than the issues associated with mixed team diving become more manageable. So, I agree with you in the sense that it all depends on the environment you dive and the particulars of the dive.

[apitkin]

Yes , but 3/3 of your bailout doesn't count for much if your extended travel exceeds your 3/3 bailout. you can achieve the same bottom/travel time with a few stage bottles at much less risk. By this standard , your cc will never be more reliable for travel than 100% of the bailout you carry in addition, on oc we have 200% of "Bailout" diving 1/3s with much less risk of failure

You can achieve the same thing on OC. Whether it's at less risk is debatable. You are too early in your cave diving career (I hope) to have been stuck in a restriction, seriously entangled or otherwise trapped. For that situation, CC beats OC hands down, especially at great depth.

The other difference is that on OC you are breathing all those stages, whereas on CC you are not. Therefore during a series of exploration dives, additional stages can be added to those already left in the cave. Almost all major cave exploration worldwide is being done using rebreathers.

Andy

[BillGraham]

What if there is a restriction and on the way out visibility is nil and the sidemount diver goes through and the rebreather diver cannot go through?

That is the near fatality we had not too long ago (it would have been the first and only one where we dive). Two RB80 DIR divers could not make it back out past the restriction due to nil visibility (and yes of course the line could have been run a little better in hindsight, but it was not), while the sidemount diver made it out (because he was leading). After he passed the restriction, in his opinion he could not wait any longer than he did or provide assistance and he exited and called in the rescue team.

Had the sidemount diver not gone through first, he would have been stuck behind the RB80 divers and the outcome would have been very different.

When I said it is a recipe for disaster it is because I have in mind the environment where I dive. However, if the environment is different and more benign, than the issues associated with mixed team diving become more manageable. So, I agree with you in the sense that it all depends on the environment you dive and the particulars of the dive.

My CCR is configured in sidemount but I can see your point.

[Shocky]

Another rebreather death here in South Florida this weekend. Supposely the diver was very expreienced in rebreathers. No other details are known.
John