Mixes >40% O2?

[PfcAJ]

IMHO this is a terrible idea. In a situation where you would have to share air with an out of air diver, and somebody was injured, explaining why you allowed a student to breath a gas they were not certified to dive might be tricky... Just my 2 cents....

Beats having to explain why there is a dead diver...

 

[kierentec]

I dont get it... Who would die if the instructor were diving air and used that to donate??

 

[Peter Guy]

Who would die if the instructor were diving air and used that to donate??

The instructor would die from DCS after doing all too many CESA attempts!

Kierentec -- Your point is, in fact, an interesting one that has several different variations.

a. I don't dive Air -- I dive 32% all the time. Given your scenario, would you be concerned that an OOA student, now suddenly breathing 32%, would have a cause of action for the injury? (BTW, putting aside the notion that breathing high PPO2 mixes could cause an injury, excluding O2 toxing issues.) What possible injury could be caused by virtue of breathing a mix as opposed to Air?

b. Diving trimix when doing deep dives with students who are not trimix certified. I, for one, am quite concerned about diving Air/EAN below 100' -- especially if I am responsible for overseeing a student at a depth down to 130' during a Deep Specialty. I don't think it is safe NOT to be on 25/25 (for example) -- but would I be doing someone "dangerous" by giving a narced OOA student 25/25 instead of Air when I was also narced?

c. I still think the benefits to me of a high O2 mix, the instructor who may be creating a personal dangerous situation by virtue of many ascents/descents, outweigh the potential theoretical liability issues from a student breathing the same mix. And I say theoretical because I can't think of any real liability issues from having a student breathing a mix that is well within the MOD.

 

[kierentec]

You're right, you would be well within acceptable po2 levels, and would most likely not cause an issue. 32% is much different than 50%, however. PADI allows a nitrox instuctor to let ow students dive nitrox on dive 4 anyways. 50% is beyond recreational limits, and if you are not a tech instructor yourself, then you should not be giving it to anybody. The issue would be during litigation when every detail of the situation was being picked apart... Just one more thing to defend yourself against. Also, if you are doing that many rapid ascents consistantly during training sessions, I would think you already have enough to worry about...

 

[fdog]

...I think that Peter is better equipped than you or I to assess potential exposure to litigation...

Peter, like you, I believe in taking the best tools for the job, and gas selection falls into that category. OW class dives w/ multiple ascents? 40%. And for the deep dive in AOW, 25/25.


All the best, James

 

[rjack321]

I'm always concerned by courses where the instructor is unwilling to dive the same gas as the student. If there's a "better choice" then the student should be on that mix too. If the agency doesn't support that choice then find an agency who's standards are aligned with the way it "should" be done.

 

[kierentec]

No, absolutely not an attorney, which may be why I'm a little more cautious about getting sued. Never been in court, don't really plan on it, either. rjack makes a good point. If it's not safe for you to dive air, then why would you allow your students to do so?

 

[fdog]

I'm always concerned by courses where the instructor is unwilling to dive the same gas as the student. If there's a "better choice" then the student should be on that mix too. If the agency doesn't support that choice then find an agency who's standards are aligned with the way it "should" be done.

It's not that there is a better gas choice for the student; it's better for me.

The students don't have to yo-yo up and down 8 times or more on the dive doing CESA training and Air-Share ascents and the like. I do. I got tired after dives like this, even with slow ascent rates; after I switched to a richer mix, I have felt better ever since.

I could breathe air, just like them, but why beat up my body like that?

As far as 25/25 goes, there is a learning lesson in taking students on air to 100'-130' for their deep AOW dives. Getting narced in a controlled situation makes for better dive planning in the future. I could breathe air or nitrox, just like them, but I see no benefit in being as drunk as them, and actually an advantage in being sharp.


All the best, James

 

[rjack321]

I know what you're saying and to a certain extent agree on the richer nitrox mix since you are not doing the same dive(s) as 1 student. You're bouncing up and down with a larger class. Of course you could have smaller classes and bounce up and down less that way too.

As far as 25/25 goes, I use it and other trimixes all the time. But I'm not really a fan of "let the students get narced so they can see what its like". AOW students diving to 100ft naturally push a little deeper and the wise ones figure out their personal limits in a measured way. If they aren't very prudent students one dive to 110-120 isn't going to change that, especially if the come up concluding they "weren't narced". Besides its not that hard for instructors to induce preceptual narrowing and other narcotic symptoms at 90ft with a little task loading and CO2 buildup. Although some agencies (again) may not support these kinds of lessons in classes.

 

[String]

Odd that their membrane wasn't capable of at least 32% Most can produce 36% even.

Might be a time factor. Membranes take longer and longer the higher the % mix required. Its not linear.

34% for example can take a LOT longer than 36% to blend and so forth.

So if they've got lots of tanks, a short time to fill then it might not be possible to blend rich.