Cave CCR - On board gas management

[Laminappropria]

What are your thoughts are on onboard gas management for cave ccr diving. Do you follow thirds like you would for other gasses? Do you follow thirds for scrubber duration? During my course no mention was made of this and now I am getting very different and very strong opinions from different people. (I dive a sidewinder and in the standard configuration you can't monitor O2 pressure during the dive.)

 

[lostsheep]

OP doesn’t want to name and shame here but I took my course with school run by the current head of training for Kiss. OP is also dives thirds on all consumables and has a transmitter for O2 however I receive a lot of pushback on the necessity of both these things from a lot of other rebreather divers. So I wanted to come to the community and hear some additional perspectives on what other people are doing.

I think your questions are completely valid but there are a lot of good reasons many are reticent.

I definitely don’t think naming and shaming is appropriate.

Have you considered reaching out to your instructor with your questions? All of my best instructors maintain a dialogue with me even several years after taking their class; I personally consider that to be an important characteristic of good instructors.

 

[Laminappropria]

Yes, I speak with my instructor often, we also dive together. Everyone is from this same of thinking, it works for them. Maybe the answer is that it just comes to personal preference and conservatism. I was just curious what other people’s experiences have been and where they fall on this spectrum.

I think your questions are completely valid but there are a lot of good reasons many are reticent.

I definitely don’t think naming and shaming is appropriate.

Have you considered reaching out to your instructor with your questions? All of my best instructors maintain a dialogue with me even several years after taking their class; I personally consider that to be an important characteristic of good instructors.

 

[kensuf]

Keeping some sort of reserves on the majority of your consumables (oxygen, stack, light, etc) is appropriate.

Thirds on dil (and onboard dil cave diving) doesn't make much sense to me, if everything is going well you shouldn't be using dil, but if it's not you'll chew through it too quickly. Additionally, cave profiles are rarely square profiles, there's frequently a bit of ups and downs. Offboarding dil and having tons of oc bailout gas are more appropriate.

I'm also in the camp that's got pressure gauges on my oxygen. Transmitters, buttons, or just old fashioned gauges. Checking it during assembly is all fine and well but what if something happens to cause it to leak in transit from your house to the dive site? I've seen that happen more than once. Yes, a gauge may introduce a failure point but I find the small risk of a gauge failure to be more reasonable than the human factors risk of not accurately checking the pressure before a dive.

Ken

 

[AJ]

Thirds on dil (and onboard dil cave diving) doesn't make much sense to me, if everything is going well you shouldn't be using dil, but if it's not you'll chew through it too quickly. Additionally, cave profiles are rarely square profiles, there's frequently a bit of ups and downs. Offboarding dil and having tons of oc bailout gas are more appropriate.

I have set a warning when my oxygen drops below 70 bars. Just as a precaution so that I know I should be heading back or losing gas. Never needed it by the way. You have to do one heck of a dive yo use 200 plus bars of oxygen on a rebreather.

I'm also in the camp that's got pressure gauges on my oxygen. Transmitters, buttons, or just old fashioned gauges. Checking it during assembly is all fine and well but what if something happens to cause it to leak in transit from your house to the dive site? I've seen that happen more than once. Yes, a gauge may introduce a failure point but I find the small risk of a gauge failure to be more reasonable than the human factors risk of not accurately checking the pressure before a dive.

Use transmitters too. They also warn me if I forget to turn on oxygen through my Nerd. I really don't need them, but they are a bonus regarding safety as far as I'am concerned.