Why not 60% O2 for prof during OW?

[RonzoTheGreat]

I think the others have hit the high points pretty well. Consider a few other reasons:

1. PADI, at least, limits training dives to three per day, so even if an instructor maxes out his/her training dives for a single OW class per day, s/he isn't going to push air NDLs in the least bit. Even if the instructor is running multiple classes on a single day, it's plenty easy to move the classes to shallower water if the instructor believes exposure time will be worrisome.

2. Surface intervals are part of the training program. You'll debrief students after every dive, and brief students on the next dive during the surface interval. And likely offgas for more time than you were on-gassing during the training dive.

3. Potential liability issues (hey, I'm a lawyer; I gotta throw it in, even though my hypo is a bit of a reach here). Suppose there's a problem and you have to put a student on your backup and ascend. The student is injured during the ascent. As a plaintiff's attorney I would attempt to question your judgment and actions in front of the jury. I would point to your use of a "technical diver mix" in a beginner's class as indicative of a general disregard of accepted entry level standards. Of course, my paid expert would also testify that OW classes should be conducted on air for various reasons, and that a reasonable and prudent instructor would not dive 60% during a certification class. Even though the 60% didn't hurt the student (which your expert would say), the jury still hears that you did something other instructors don't do. That's bad for you, because it makes a jury less likely to believe that you acted within standards at all times.

you're a bastard ..... a good lawyer but a bastard ... why? because your point (#3 anyway) is so damn vaild ... in the US .... grrrrr

so i guess thats the end of this conversation, no need for anyone to write further on this ....

but i did expect your first answer ... NDLs are not a bible or scientifically proven, they are based on theory ... (maybe a tinge of devil's advocate from who i really am)

 

[RonzoTheGreat]

I have known and assisted instuctors who will do check out dives with multiple classes in one day ......

and besides, who said any of the students were even going to know the instructors were using nitrox? I doubt the investigators will confiscate and anylze the istructors tanks if the student had the problem.

this tells me you have never witnessed death underwater ... im happy for you. i hope it never does cross your path.

for the record, if something drastic does occur, and it is found that the "student" was breathing off your octo or such, YES, they will analyze your back gas, and your sling if you use one.

 

[AzAtty]

If the inquiry is physiological only, then the primary risks are CNS and pulmonary O2 toxicity. Those are a function of partial pressure and exposure time. Consider also that high oxygen tensions cause coronary vasoconstriction, but I have no idea of the extent to which (or even IF) such would affect a diver within the parameters you have given; my doctorate is in law, not medicine.

Other than the toxicity concern, I don't believe there isn't anything physiologically "wrong" per se with high O2 gasses on shallow dives. Historically, combat divers experienced significant exposure times while using oxygen rebreathers on demolition missions without apparent ill effect. On the other hand, divers have seized within "accepted" limits.

The "thinking diver" should consider possible consequences that are not directly related to use of a high O2 mix. The justification offered for breathing a high O2 mix appears to be (a) the ability to stay submerged longer and (b) an increased margin of safety against DCS. However, the ability to stay submerged for hours on end is absolutely irrelevant if the environment is not conducive to such a stay (e.g. cold, surge, tides, waves, etc.). There may be other factors outweighing the primary benefit of a high O2 mix (extended stays).

 

[AzAtty]

you're a bastard ..... a good lawyer but a bastard ... why? because your point (#3 anyway) is so damn vaild ... in the US .... grrrrr

Thanks

but i did expect your first answer ... NDLs are not a bible or scientifically proven, they are based on theory ... (maybe a tinge of devil's advocate from who i really am)

I don't think anyone will disagree with you. Bruce Wienke writes that we presently lack the technology and computing power to accurately model the body's responses to compression and decompression. The best any modeler can do is observe the data, choose a statistically acceptable incidence of DCS, and run with it.

 

[Blackwood]

Bruce Wienke writes that we presently lack the technology and computing power to accurately model the body's responses to compression and decompression.

Hell, we can't even predict tomorrow's weather with any reasonable certainty.


(Though Al Gore seems to know something about the weather far in the future).

 

[AzAtty]

Hell, we can't even predict tomorrow's weather with any reasonable certainty.


(Though Al Gore seems to know something about the weather far in the future).

I can predict the weather with a great degree of accuracy: sunny and warm. But that's only for Phoenix, Arizona and Death Valley. And Kuwait.

And since Al Gore invented the Internet, you should not be surprised that he can predict future weather. I also heard that the weather changes to match Chuck Norris' predictions. Maybe we should get him to make up a dive table.

 

[Anti-Hero]

I think the OP either a) already knows it all, or b) doesn't want to learn. He keeps sighting some ambiguous "bio" effect of 60% O2 for instructional diving.

The biological effects are: Elevated PP02, Toxicity (CNS/pulmonary), inert on gassing differences relative to air, etc. But the op continues to dismiss the math for some inane personal experience semantics.

 

[rjack321]

N2 is not my friend ... i DONT want to think about theoretical depths and times for off gasing ...

the less N2 the better (barring depths and times exceeding O2 allowance)

No?

No. By your logic the OW skills dives like mask replace etc (<30ft) should be done on 80%, which would be awful hard on the instructors body.

O2 is even less of your friend than N2

She will give you pulmonary edema
vision problems
auditory disturbances
nausea
twitching
irritiability
dizziness
And possibly all sorts of nervous fits and drowning

I would not flirt with the edge of the O2 sword without a good reason. And merely to reduce N2 (all day long) is not adequate justification.

I don't know where you got this EAN60 number in your head from but since its MOD is less than the depth checkout dives are conducted at its definately imprudent. EAN36 would at least have some rationale backing for it. Seeing as its MOD is far below an OW class/dives usage, has a MOD buffer to account for wayward students, and CNS clock buffer to allow for all day use. Not to mention its not a "technical mix" and most nitrox capable shops will be familar with it to make it without a booster.

 

[dwhthediver]

Using 60% while working with o/w students is a can of worms not needed, wayward students, steam engine breathers, too many possibilities of AIS(a** in sling) to deal with, keep the mix low enough to be within the recreational nitrox. A lot of instructors do use those mixes, and won't create an increased civil liability issue, (you know dealing with the sharks without fins). Sorry, AzAtty, could not pass up the shot at the bar's finest.

 

[AzAtty]

(you know dealing with the sharks without fins). Sorry, AzAtty, could not pass up the shot at the bar's finest.

No worries; just so long as we are properly feared.