Nitrox - What do you dive PO2 - 1.4, 1.5 or 1.6?

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Basking Ridge Diver

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I was reading an article that talks about PO2..

Instruction: CNS Oxygen Toxicity | Scuba Diving
This point stuck out at me -
"Please note: There is no more danger with a 50 percent exposure to oxygen at 1.6 than there is with a 50 percent exposure at 1.4 or 1.3. It's the total dose, not the PO2 that determines your risk factor."

I called a local LDS and inquired about one of the dives for this summer - he said to the sand is 130ft so you would be diving 28% Nitrox - which is 1.38 PO2... Would I be allowed to dive 30% at 1.5 or is that pushing the limits?

So I am wondering do most folks dive 1.4 for conservationism or is the article above misleading?
 
The commonly accepted ppo2 is 1.4 or less for the working/ swimming/ stressful portion of the dive. 1.6 is the accepted ppo2 for the restful / deco portion of a dive. A lot of other things come into play here, so these are guidelines only. These guidelines are wildly subjective by region, and depth. In Fla. diving 1.6 all the time for rec dives is fine, in the north east not so much.
YMMV
Eric
 
That quoted paragraph is bs.

50% at a 1.0 isn't going to do anything to you. 50% at a 3.0 can be fatal after a relatively short time period. The "dose" is 3x per given time period.
 
As I have learned more about various things in diving, I've become, in many cases, more cavalier than I was as a new diver. One exception is with ppO2s -- when I read more, and looked at the results of the studies which have actually been done, and read some case reports, I realized that, in reality, we don't have much of a clue as to what is going on with oxygen toxicity. The ppO2 limits were set by finding a value where no one had been known to tox; in fact, there is at least one case of a fatality from an underwater seizure at 1.4. The "oxygen clock" is essentially arbitrary -- no one has studied masses of people exposed to various ppO2s for various periods of time, to see if those limits are either safe or unduly conservative. The studies which have taken human subjects to depth on various ppO2s involve extremely small numbers and show such variability from day to day and diver to diver as to be really terrifying.

1.4 for working depth for this lady, and I rarely get there, and even more rarely for any length of time. 1.6 on deco. CO2 seems highly likely to potentiate oxygen toxicity, so any time I'm exerting, ppO2 needs to be well away from limits.

You can survive the bends. You are highly unlikely to survive an oxygen seizure.
 
o2 is one heck of a mystery.

1.2 (or less) on the bottom for me, 1.6 (or less) for deco.
 
That quoted paragraph is bs.

50% at a 1.0 isn't going to do anything to you. 50% at a 3.0 can be fatal after a relatively short time period. The "dose" is 3x per given time period.

Actually, it's more like a ton of feathers vs 2000 lbs of lead. 50% of O2 exposure is the same, regardless of the PPG. You'll just achieve 50% faster at a higher PPG, assuming the same depth.
 
If I did your bottom times, AJ, I'd do 1.2, too.
 
Oh, and to answer the question of: 1.2 for working and salvage, 1.4 for recreation and 1.6 for deco
 
Actually, it's more like a ton of feathers vs 2000 lbs of lead. 50% of O2 exposure is the same, regardless of the PPG. You'll just achieve 50% faster at a higher PPG, assuming the same depth.
Ah ok, I read it as the gas was 50% and it was arguing that 50% at a 1.3 is somehow the same as breathing 50% at a 1.6 because the fo2 is .50.

---------- Post added February 14th, 2015 at 08:26 PM ----------

If I did your bottom times, AJ, I'd do 1.2, too.

Just a function of standard gases, that's all :)
 
https://www.shearwater.com/products/teric/

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