What O2 partial pressure do you use for Nitrox Calculations

[scuberd]

ElectricZombie once bubbled...
Unless they have changed it, NAUI recommends 1.4, not 1.6.

1.6 is for emergency/contingency issues or deco only.

What University is recommending 1.6?

It's UC Santa Cruz, and they mandate no more than 1.4, but they would probably allow 1.6 in an emergency

 

[The Chairman]

How many of you have actually exceeded (or even gotten close to exceeding) your Ox-clock??? Only if I am doing a BOATLOAD of dives over more than one day have I ever come close. I don't even calculate it for a two tank dive trip... unless I am diving the next day. Of course, my Cobra would warn me about it, so I am not that "at risk".

 

[kkrepps]

One of the things I was interested in when I posted this poll was the relationship between O2 PP limit and MOD in the context of recreational diving. Using the MOD formula contained in the PADI Enriched Air Diver Manual with say 32 % O2 @ 1.4 ata the MOD is 111fsw at 1.6ata its 132. What is your comfort level?

 

[SDAnderson]

My personal ppO2 limits:

1.2 cold-water working
1.4 warm-water working or cold-water resting
1.6 warm-water resting

NOAA limit is 1.6 for a working diver - I've rarely felt the need to plan for a dive that high.

It takes a lot of exposure to have to worry about the O2 clock, at a ppO2 of 1.40 you can be in the water for something like 2 1/2 hours on a single dive, slightly higher for a 24 hour exposure limit. That's pretty serious diving - even if you're running perfectly square profiles. Those diving EAN on liveaboards or planning lengthy decompressions might need to watch pretty closely and take an occasional break from the high O2 gas, but for most of us Ox-Tox clock is not much of an issue.

Steven

 

[Charlie99]

scuberd once bubbled...
It's UC Santa Cruz, and they mandate no more than 1.4, but they would probably allow 1.6 in an emergency

So if your buddy goes unconscious and starts sinking deeper, do you stop at 1.6??

While oxtox data at higher PPO2's is hard to get, my real rock bottom emergency limit is more like 2.2ppO2/5 minutes if someone's life depended upon it. With a gas like EAN32, that means I would hit narcotic depth and gas supply problems before ppO2 keeps me from going after him with a single AL80.

Even with EAN40, the 2.0ppO2 is 132', and 2.2 is just under 150'. Obviously, I'd do this only in truly extreme circumstances, and I would spend no more than 5 minutes, but thinking out "what would I do" type scenarios ahead of time is a good idea.

A good question to ask yourself is "what is my true emergency limit?"

Charlie

 

[plsdiver4377]

1.4 according to my training(NAUI) for the MOD, but diving on air tables.

 

[Stone]

NetDoc once bubbled...
How many of you have actually exceeded (or even gotten close to exceeding) your Ox-clock??? Only if I am doing a BOATLOAD of dives over more than one day have I ever come close. I don't even calculate it for a two tank dive trip... unless I am diving the next day. Of course, my Cobra would warn me about it, so I am not that "at risk".

Last week, I made three dives on 35%. I'll have to check my computer, but my clock was showing about 3/4 of max. I'll probably drop down to 33% or 34% for my 4-tank days.

 

[Big-t-2538]

I see no reason for a recreational diver to ever be planning for a ppo2 of higher than 1.4.

As for the technical realm (which I have a lot of learning to do before I even consider going that direction), the general consensus is 1.4 during the dive and 1.6 deco....but only during deco is the ppo2 higher than 1.4

 

[O-ring]

...but I used to. We shoot for 1.2 or 1.3 for bottom mix/working portions of the dive for added conservatism. With deco diving, the extra minute or two hang is worth it to me to not push the oxygen. However, I can understand that recreational divers wanting to stay within the NDLs may push 1.4 or higher to maximize bottom time. IMHO, that is a personal choice, but for me, I stick with 1.2 - 1.3.

 

[Charlie99]

Stone once bubbled...
Last week, I made three dives on 35%. I'll have to check my computer, but my clock was showing about 3/4 of max. I'll probably drop down to 33% or 34% for my 4-tank days.

NetDoc once bubbled...
Of course, my Cobra would warn me about it, so I am not that "at risk".

The Cobra and other Suunto computers will let you violate the NOAA 24hour CNS limits and still show you as being well into the green zone of the CNS bargraph.

If you were showing 3/4 of max on a Suunto,then you probably had exceeded NOAA limits.

Charlie