Nitrox to an OOA Diver?

[Rainer]

There is NO reason to have an O2 bottle on at depth.

Makes the RB a lot easier to use, though...

 

[Drewski]

Unfortunately, there seems to be a bit of misinformation getting passed around in this thread.

Jax, I responded to you like I did because you are treating a serious subject very flippantly and I really need to question if you understand the risk you might be placing yourself and potentially others in.

A "pony" bottle (as you call it) is usually attached to a tank and used only for emergencies. As a result, it probably doesn't get refilled all that often. A "deco" bottle is generally slung and used regularly, so gas mixtures change with each fill.

At 40% O2 you have a MOD of roughly 80 FT with a PPO2 of 1.4. 90 FT for 1.5 and 100 FT for 1.6. So, if you are ONLY diving that "pony" in less than 80 FT of water all the time (like at your local dive sites), and that was a convenient gas when you filled it, OK, I might see your point (even though I disagree with it).

But if that's NOT the case, you are putting both yourself and anyone you share that gas with at risk, anytime it's used below 80 FT. And that's not the purpose of using a "pony" as an emergency gas source, is it?

Look, you might see posts here that saying that O2 tox hits are very rare for short exposures and any PPO2s of 2.0 or less. I'm not going to get in a big discussion about it, but that's just NOT true.

Over the winter I was doing trimix training dives with another instructor in Florida at 40 Fathom Grotto. Another team had just descended for a side-mount training dive using air to 150 FT. They had planned a decompression gas switch to 32% at 120 FT, briefly putting them at a PPO2 of just under 1.6. One student did the switch, took 3 breaths from the regulator and immediately "felt strange." She switched back to air, but within 10 seconds went unconscious and seized underwater. The instructor saved her life by rocketing to the surface, punching her gut and missing both of their 15 min deco obligations. When she reached the surface, she was unconscious, not breathing and obviously blue. Fortunately, 40 Fathom is an incredibly well prepared facility with full medical gear. We successfully resuscitated the student on the surface, followed by transport to an Orlando chamber. She walked out at 100% 2 days later, damned lucky to be alive. If that had happened on a boat in the ocean, she would have died. Her total cost in medical bills exceeded $30K.

I spoke with the student by phone several weeks later. She indicated she had done "many" deco dives with PPO2s between 1.5 and 1.6 with no unusual effects. She had logged more than 500 dives, more than half below 100 FT. When it happened, she reported no symptoms, just a "rush" followed by waking up in the hospital with a sore throat. Her gas analyzed as normal, with no impurities, and at the O2 percentages labeled on the tanks.

The FACT is that O2 toxicity hits are unpredictable. They don't always follow previously experienced limits. Many factors influence toxicity and on THAT particular dive they all lined up for her.

Jax, you chose to post this thread in a Basic discussion board. So lots of folks out there without your experience are reading it and probably "learning." Some of the replies to your post are equally as nonchalant to the issue. Some are much better.

Nitrox and other mixes are great to use if you have the training, experience and understanding of how to use them.

40% shouldn't be in a "pony" bottle just because the sticker looks cool...

Good luck with your dives in the future and stay safe.

 

[Jax]

I had a very specific question about a situation. I didn't ask for input on my gas choices, and I would appreciate it if you simply accept I know what I am carrying and plan accordingly. Yes, I was flippant with the undesired input.

For those of you that did address the question I asked, I thank you. Your answers were pretty much in line with my thinking but I value highly the various opinions of this board. I also am greatly warmed by the concern expressed by those that did express it as concern. For those that came across as chiding, :talktothehand:.

 

[Cave Diver]

Sadly its not original.

Any guesses who first used that phrase?

Do we get III guesses?

I had a very specific question about a situation. I didn't ask for input on my gas choices, and I would appreciate it if you simply accept I know what I am carrying and plan accordingly. Yes, I was flippant with the undesired input.

For those of you that did address the question I asked, I thank you. Your answers were pretty much in line with my thinking but I value highly the various opinions of this board. I also am greatly warmed by the concern expressed by those that did express it as concern. For those that came across as chiding, :talktothehand:.

You've been on this board long enough to know that when you post a question you'll often get undesired input. You've been guilty of providing that yourself at times.

You may know what gas you're carrying but that doesn't mean we have to accept it as a good idea. I think we'd be negligent to not point that fact out to others who may be reading along and lack your insight and wisdom on such matters.

 

[ianr33]

Do we get III guesses?

Of Course !!!

Who could ever forget this post (or sleep after seeing it )

The Deco Stop

 

[Dominantly]

Thanks for everyone taking the time to post up information expanding the details of the OP's topic.

 

[jonnythan]

At the risk of going horribly OT, anyone know what our friend GI is up to these days?

 

[Sas]

At the risk of going horribly OT, anyone know what our friend GI is up to these days?

Probably stirring up trouble on fishing email lists?

 

[Rhone Man]

Over the winter I was doing trimix training dives with another instructor in Florida at 40 Fathom Grotto. Another team had just descended for a side-mount training dive using air to 150 FT. They had planned a decompression gas switch to 32% at 120 FT, briefly putting them at a PPO2 of just under 1.6. One student did the switch, took 3 breaths from the regulator and immediately "felt strange." She switched back to air, but within 10 seconds went unconscious and seized underwater. The instructor saved her life by rocketing to the surface, punching her gut and missing both of their 15 min deco obligations. When she reached the surface, she was unconscious, not breathing and obviously blue. Fortunately, 40 Fathom is an incredibly well prepared facility with full medical gear. We successfully resuscitated the student on the surface, followed by transport to an Orlando chamber. She walked out at 100% 2 days later, damned lucky to be alive. If that had happened on a boat in the ocean, she would have died. Her total cost in medical bills exceeded $30K.

I spoke with the student by phone several weeks later. She indicated she had done "many" deco dives with PPO2s between 1.5 and 1.6 with no unusual effects. She had logged more than 500 dives, more than half below 100 FT. When it happened, she reported no symptoms, just a "rush" followed by waking up in the hospital with a sore throat. Her gas analyzed as normal, with no impurities, and at the O2 percentages labeled on the tanks.

The FACT is that O2 toxicity hits are unpredictable. They don't always follow previously experienced limits. Many factors influence toxicity and on THAT particular dive they all lined up for her.

That is a very odd story. I don't disbelieve you for a second, but I have never heard of anything remotely like it before. Toxing after three breaths at 1.6? Very odd indeed. Wonder if the reg could somehow have become charged with pure O2.

Not undermining your cental point though - O2 hits are unpredictable. But as has been noted above - beats the hell out of drowning.

 

[peterbj7]

At the risk of going horribly OT, anyone know what our friend GI is up to these days?

Is he out of diving then? I thought it had been quiet lately.