Need Help with Nitrox

[ianr33]

See, this is what I'm talking about. By working, do you mean you use a ppo2 of 1.3 if you're working as an instructor? Or do you mean if you are breathing heavy, i.e. exerting effort?

"Working" in this context generally means "swimming", even slow swimming.

During deco you are generally "resting" i.e. just hovering in place or hanging on a line (Or in a cave taking a nap on the bottom )

 

[scubadiver888]

1.4 is a pretty standard MAXIMUM for bottom gas.Going to 1.5 or 1.6 for a few minutes won't kill you but its best not to plan on it.
1.6 for deco is also pretty standard

If I was doing a couple of HOURS bottom time then I would drop the pO2 to 1.2 or thereabouts, but for recreational diving or "regular" deco dives 1.4 is fine. YMMV.

Thanks. This makes a lot of sense. The tech diver who told me 1.2 was diving double 130s for his bottom gas and I'm not sure what he was slinging but they were fairly large. He did one dive were as we did two on the same site with a surface interval.

 

[Tortuga68]

So you would never personally use a pO2 in excess of 1.6? Might that be dangerous?

Is that the best you can do?

 

[DaleC]

Someone needs some better bait.

 

[kanonfodr]

Thanks. This makes a lot of sense. The tech diver who told me 1.2 was diving double 130s for his bottom gas and I'm not sure what he was slinging but they were fairly large. He did one dive were as we did two on the same site with a surface interval.

As others have stated, for longer or repeated exposures many divers prefer to play it safe and back off of the bottom pO2 by either diving shallower or using a mix with less O2 content. This is to lessen the chance of both CNS and Pulmonary Oxygen Toxicity. Also, some people are simply more conservative than others so for a "normal" dive their working pO2 may be 1.2, and for more aggressive or longer dives they may back it off to 1.0.

To the OP: In your case, if you are concerned about your bouyancy skills I really can't recommend taking a leaner mix for the dive as a long-term solution, that's a band-aid solution on a pressure dressing problem. I would urge you instead to work on your personal skills (trim, bouyancy, situational awareness), perhaps finding a mentor or instructor who could dedicate some time to focus on those issues.

And oh yes, and go get your money back from your nitrox instructor. Or finagle some free time working on the theory section of your Nitrox materials and possibly some in-water work as well out of him.

Peace,
Greg

 

[scubadiver888]

Is that the best you can do?

How about...

I don't worry about my ppo2. I just watch for oxtox and when I feel it coming on I go back up.

 

[Tortuga68]

Yes, you'd probably have better luck getting someone to bite on that. But Ian was specifically attempting to get me to bite, and neither will work for that

 

[TSandM]

that's a band-aid solution on a pressure dressing problem.

That's a wonderful phrase, and I'm going to shamelessly borrow it!

 

[nshuff]

Sure its not set to air?

Yes, it is set to ean 32.

 

[dschonbrun]

If you use a Max PP02 of 1.2, On 32%, the MOD is 90 feet.

At 100ft = 30m = 4.0 ATA, the max % of 02 is 30%. For 82 ft = 25m = 3.5 ATA, the Max % of 02 is 34%. (again, based on MOD @ PPO2 of 1.2)

I hope this helps you to figure out your recreational depth floors. You should be able to do this as part of the Nitrox course. If you're having trouble, please speak to your instructor and review the formulas, and the theory behind them.