Setpoint during fast decent, what do you use?

[Agro]

calculating your "exact" planned arrive ppO2 on the bottom isnt part of that.

If my wreck is at 60m on flat sand I do know my target depth and I do know I will not be able to go 1m deeper. Same situation in some caves.

 

[grantctobin]

21 is not a crazy hot dil for 60m.
35 ist not a low fraction of he. END is perfectly OK. I even dive 60m on air, OC and CCR.

What is this 1995?

 

[berndo]

I have no idea why the OP is bumping up the ppO2 shallow then adding a crazy hot dil with such a low fraction of helium.

Having seen some of his other threads (and this one), it seems that he hasn't gotten any ccr training but is self-taught by reading stuff on the internet. The O2 'strategy' really doesn't make much sense and neither does low He dil/high END/high gas desinty on a CCR, IMHO.

 

[Wibble]

No problem with that. Metabolism brings it down to 1.3

Eventually it will. But slowly.

The current thinking is to keep the PPO2 lower for the deep portion of the dive for other reasons than just shortening decompression. Keeping the CNS+POT (pulmonary oxygen toxicity) down; CO2 hits apparently are worse or triggered by high PPO2; WOB (work of breathing) with a larger helium fraction.

But most importantly, having a lower diluent PPO2 means you can correct the loop should the crap hit the fan -- brain fart and inject too much O2; or the solenoid injects just as you descend to the bottom of the wreck; broken solenoid, leaky injector, etc.

 

[berndo]

I even dive 60m on air, OC and CCR.

Bounce dives to 60m on OC is one thing (if you need it for your ego), I used to dive below 60 m on air too, but air dil on a ccr is just stupid. He dil is cheap. What's the point in using high density dil and diving completely hammered on a CCR? What's even the point in using a rebreather to begin with when you're doing deep dives on air? The whole story is weird.
It's like drunk driving on a motorbike in shorts.

 

[Agro]

Having seen some of his other threads (and this one), it seems that he hasn't gotten any ccr training but is self-taught by reading stuff on the internet.

Nonsense, I got serious CCR training on 2 different rebreathers. I ve been diving CCR for 25 years. And I am more than willing to learn new stuff.

 

[formernuke]

Frankly speaking then why do your post go against commonly established safety rules.

 

[Agro]

Eventually it will. But slowly.

The current thinking is to keep the PPO2 lower for the deep portion of the dive for other reasons than just shortening decompression. Keeping the CNS+POT (pulmonary oxygen toxicity) down; CO2 hits apparently are worse or triggered by high PPO2; WOB (work of breathing) with a larger helium fraction.

But most importantly, having a lower diluent PPO2 means you can correct the loop should the crap hit the fan -- brain fart and inject too much O2; or the solenoid injects just as you descend to the bottom of the wreck; broken solenoid, leaky injector, etc.

Sounds good, no doubt. If I make a long dive (for ex cave) I have the CNS problem and will keep the pO2 lower. Or I take the risk of high CNS which in certain cases is OK as well. If I make a short dive CNS is not involved.

CO2 hits: I didn't know that. Is there any serious study about this?

Solenoid stuk open at 30 or 100m: is there really a difference between having 1.1 or 1.3 in the loop? I guess pO2 goes up very, very high anyway. I guess=I don't know.

 

[Agro]

but air dil on a ccr is just stupid.

Normaly I dive 21/35 from zero to about 60m. I only use air if 21/35 is not available. But then I use it without any problems at all.

Deeper than 60m is for 18/45, if available

 

[barth]

Normaly I dive 21/35 from zero to about 60m. I only use air if 21/35 is not available. But then I use it without any problems at all.

Deeper than 60m is for 18/45, if available

Mod for 21/35 is 30 meter as dilluent for GUE ccr divers. The mod of 18/45 when using as diluent is 45 meter for GUE ccr divers.

My GUE ccr doubles contain 15/55 which has a mod of 60 meter when using as diluent.