Air strategy for 4-5 tank dive days?

[CajunDiva]

Why is it even an issue? Set your primary computer to the nitrox % you are using and set your BACKUP computer to air. Then compare the two!

Ahhhhh...a NEW can of worms

 

[BRT]

The depth the DM may have been talking about was probably with regard to first dives. Second dives generally have a floor. There are exceptions, of course but for the most part, that's what happens. You'll likely be doing those 2nd and 4th tanks at reefs with a floor that's above the MOD. Was that DM doing 4 tanks per day? If a DM is doing a 4 tank day, the shop I use sends them out with 2 tanks of nitrox for the 2nd and 4th dives.

Let's assume you decide to dive nitrox one tank out of 4 and the shop knows this. When you ask for tanks of 32%, it may be suggested that you dive that tank on 36% as the cost is the same whether it's 32% or 36% and you'll get a little NDL benefit.

In a vacuum, one can plan just about any mix for any dive. Thing is, you're not diving in a vacuum. There are other divers on the boat. That said, it's not impossible to get on a boat and all the tanks on that boat are Nitrox. The dive plan would take that into consideration. i.e. you won't be diving Devil's Throat that trip.

Contact 3Ps and get their input. My understanding is that they're quick to respond.

You have never done DT on nitrox?

 

[gopbroek]

Oxygen Toxicity, just like DCI, is a gray science - no two divers react the same. As long as you stay above the MOD, DCI is the monster you should educate yourself about. There's a guy sitting in the chamber in Cozumel right this moment, 65' dive no nothing profile from what I hear, healthy active man with possible kidney failure.

I hope for a positive outcome for this diver but unfortunately I think it is much more likely that a chamber will be occupied by a diver who takes a 'random hit' than a diver who has actually violated the tables.

 

[ChuckP]

I hope for a positive outcome for this diver but unfortunately I think it is much more likely that a chamber will be occupied by a diver who takes a 'random hit' than a diver who has actually violated the tables.

Not sure if you're familar with Cozumel my Cozumel, ladies name is Paula that runs the site - it was her husband. Curious to see the profile and hear about activity before and after the dives. She said it was 65' easy profile BUT there was a second dive too, 50 minute surface and shallower but wonder when symptoms started and what they were. He's out now and at home.

And I'd tend to believe you're 100% correct on the random thing......

I also wonder, just cause there's a chamber there and ambulances staged at the Money Bar and marina, do they error on the side of caution by giving chamber treatments???

 

[nodakdive]

You have never done DT on nitrox?

No, Only air.

 

[BRT]

No, Only air.

I've only been through once, on 32%.

 

[nodakdive]

I've only been through once, on 32%.

7 feet below the MOD for a few minutes probably isn't the end of the world. Would you do it on 36%?

 

[BRT]

7 feet below the MOD for a few minutes probably isn't the end of the world. Would you do it on 36%?

No, I only hit 126 on 32%, stayed high. I know in my head I'm in more danger from narcosis or DCI than O2 toxicity, but I'm not much of a limit pusher. I'd do it again on 32% without a 2nd thought.

 

[northernone]

I'm concerned by the trend of some in this thread to downplay the risks of oxygen toxicity and advocating to 'wing it' with rough guesses instead of using the tools they have the way they were trained to.

I would need research showing the risk is insignificant when diving 36% like it is 21%. I don't like blind luck and my own guesses determining what's 'safe enough' oxygen exposure when all the while I'm carrying a device programmed to quantify this risk according to the best current understanding of the risk. Why not program the gas you're actually breathing and add conservatism to your dive profile by consciously staying further away from the NDL?

One rhetorical question and one incredulous question:

Why do recreational computers track oxygen exposure? Why do some feel this feature is unnecessary and can be ignored (by falsifying % input data)?

(Sidebar: dove gladly at ppo2 1.6 today)

Cameron

 

[The Chairman]

Wasn't nitrox also relatively poorly accepted 15 years ago?

More like 20.

Why do recreational computers track oxygen exposure?

Most divers never violate the CNS clock. It requires fairly aggressive diving including lots of deco. It's there for the very few who do. I don't know that I've heard of any diver falsifying % to get around that.
I do know many divers who violate depth limits. Most do fine, but there are always a few who don't. That's the beauty in a rebreather: always the best mix and there's no need to violate those PPO2 limits.