Follow the rules and you'll never feel it.
Air break on rebreather, how to proceed?
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Follow the rules and you'll never feel it.
cruisekingkris
Contributor
Haha.
did I just get an instructors “do as I say and not as I do”.
Just kidding. I need more bottom time. A little hot lung ain’t stopping me.
did I just get an instructors “do as I say and not as I do”.
Just kidding. I need more bottom time. A little hot lung ain’t stopping me.
he’s saying follow the open circuit rule or 15 or 20 on oxygen 5 off and you’ll never feel it. CCR he ignores the rule because it’s a different animal
Nope. I follow the rule for OC. There is no rule for CCR
Dsix36
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I would like to correct you since there is indeed a rule for CCR, even though it does not pertain to air breaks.
Always know your PPO2 !!!
Very good thread, thank you. But as I expected there is not one single truth.
I think I will start doing airbreaks on rebrether as well. But I'd like to stay on CCR so I will lower the pO2. And here is the next problem: which pO2 shall I use? An AIRbreak is done on air. In a CCR I will not go down to 21% of oxygen. Perhaps I will run it on 0.4 pO2 but is this an airbreake?
I think I will start doing airbreaks on rebrether as well. But I'd like to stay on CCR so I will lower the pO2. And here is the next problem: which pO2 shall I use? An AIRbreak is done on air. In a CCR I will not go down to 21% of oxygen. Perhaps I will run it on 0.4 pO2 but is this an airbreake?
Breathing air at a depth of 20' yields a PO2 of 0.34. At 60' it is 0.59.
You'ld have the same effect just switching down to your lower O2 setting. I use the 0.4 and 1.3 settings on my RBs and don't have a problem.
Sure if I was doing long RB dives a PO2 of 1.3 would be excessive while not on the deco portion, but with my current cold water dives I'm always out of the water within 150 minutes.
Michael
You'ld have the same effect just switching down to your lower O2 setting. I use the 0.4 and 1.3 settings on my RBs and don't have a problem.
Sure if I was doing long RB dives a PO2 of 1.3 would be excessive while not on the deco portion, but with my current cold water dives I'm always out of the water within 150 minutes.
Michael
barth
Contributor
Why should you change it to 0.4 ? Even if I use ean32 during a gas break when diving OC my po2 is 0.5....
My hud buddy warning light will be red during a gas break when I would use a 0.4 setpoint. My own hud leds will also be red.
I think 0.7 is much safer and give more margin when something goes wrong....
Air breaks or back gas breaks seem to be only advocated for when using 100% for extended periods IME. Nobody seems to advocate it’s use on 50% to my knowledge.
My take and what I teach my students for CCR is NOT to run a 1.6 for deco as the risks and negatives far outweigh the relatively small deco benefits. In the exposures I am dealing with (60m dives with 60-90 min TTS) I really find no advantage to running 1.6 and there are several potential issues.
That all being said, individuals vary. Run some plans on 1.2 throughout vs 1.6 on deco. If the deco saving is worth the CNS exposure and OTU exposures for you, then I would suggest seeing if you have any issues before trying to do gas breaks.
If you have a bailout that’s a reasonable PPO2 at the 6m stop then I would use that rather than changing PO2 with all the buoyancy futzing that’s comes with it.
My take and what I teach my students for CCR is NOT to run a 1.6 for deco as the risks and negatives far outweigh the relatively small deco benefits. In the exposures I am dealing with (60m dives with 60-90 min TTS) I really find no advantage to running 1.6 and there are several potential issues.
That all being said, individuals vary. Run some plans on 1.2 throughout vs 1.6 on deco. If the deco saving is worth the CNS exposure and OTU exposures for you, then I would suggest seeing if you have any issues before trying to do gas breaks.
If you have a bailout that’s a reasonable PPO2 at the 6m stop then I would use that rather than changing PO2 with all the buoyancy futzing that’s comes with it.
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