Why not 60% O2 for prof during OW?

[boulderjohn]

Perhaps, but oxygen toxicity isn't something that magically happens when you cross some arbitrary boundary like 1.4 / 1.6 PP02.

That's why I said the results "might" not be all that good.

 

[AzAtty]

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.

 

[Anti-Hero]

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

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.

Excellent point. I didn't even think about the potential liability of it. The instructor gave the student gas the student was not properly trained or certified to use... hmm... interesting!

 

[AXL72]

Yeah...why the question (oops..I mean conversation...yeah, like, why we conversing about this?) and the 60%?

Seems like asking, 'why not drive in city traffic with jet engines outfitted on your auto?'


Was there an axe to grind here?

 

[DA Aquamaster]

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.

I have known and assisted instuctors who will do check out dives with multiple classes in one day and/or split up the class for more 1-1 attention - especially in low viz. So while a student may be limited to 3 dives per day, an instructor and DM doing 6 a day would not be uncommon. That can be a lot of up and down when doing CESA drills and 36% or 40% nitrox is not a bad idea and still allows you to go a bit deeper than the course standards to retreive a wandering student. It is not so much the exposure time that presents the risk but rather the frequent sawtooths over the course of several repetetive dives. And in the case of multiple classes on one day, the SI tends to be short.

I agree with you with regard to the liability issues using 60%. And it probably also true that an ambulance chasing/muck raking attorney may try to develop a case and influence a jury to find in favor of a plaitiff using an argument that 32%,36% or 40% nitrox contributed to the accident, but it is a bs argument - 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.

 

[RonzoTheGreat]

Something to consider is the total depth of the water, not just the depth of the students. Let's take a popular New Mexico instructional site, the Blue Hole. It has a maximum depth of 87 feet, with OW students working off platforms at much shallower depths. An instructor working a lot of classes might be tempted to use 60%. So the instructor is doing the tour portion of the dive, and suddenly a student has a buoyancy problem and starts to plummet. The instructor dutifully chases, and before long is below the MOD (maximum operating depth) for 60%. What follows might not be all that good.

i was hoping NOT to get answers like this as it is an "advanced discussion" so i figured that point was presumed ...

but, since it isn't ... the teaching zone max depth would be 53'

 

[RonzoTheGreat]

Huh?

Tables and consumption are theory? Tables are perhaps theory backed by a lot of empirical data but consumption calculations are pretty solid given a known SAC rate. However "proven" as in feeling better is anecdotal at the very best. I do *think* I feel better after diving a rich mixture, but there is little science to back it up. Is that a proven quality or is that a placebo effect since i think I'm going to feel better?

The other basics like exposures (as in breathing 60% O2) are far more relevant to this "conversation," especially the "bio side."

I guess I'm just not following what exactly you're asking, or why you picked 60%? Was it just some arbitrary mix for conversation?

yes, as a matetr of fact, the 60% was just arbitrary, thanks for asking ...

the bio side of it is exactly what i am focused on, and

yes, i do believe it is placebo to feel better after diving higher O2 mixes,
BUT, since we are all different, who's to say it doesn't effect me differently and maybe you really DO feel better ...

back to the origin, why not dive 60% if available and max depth floor of 53'

 

[RonzoTheGreat]

Ronzo,
A friend and I sometimes to use mixes to 40% and sometimes a little higher. We mix our own deco bottles, and when the pressure gets too low in the O2 tank, we mix what we can for shallow dive backgas. When topping with 36 it is very easy to go over 40%. The only real benefit is a very low N2 load at the end of a couple dives.

thanks for this, it is exactly what my thought was/is .... N2 is not my friend ... i DONT want to think about theoretical depths and times for off gasing ... i HAVE to for deep dives, but for a simple OW class, why not right?

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

No?

 

[JeffG]

i was hoping NOT to get answers like this as it is an "advanced discussion" so i figured that point was presumed ...

but, since it isn't ... the teaching zone max depth would be 53'

Thats nice, but real life has a way with throwing your internet plans a curve.

I remember a class a buddy of mine was teaching in BC. A couple of students went over a wall and had to be chased down by a DM. IIRC, it was at 80' the DM caught them and thats because it was the bottom.

 

[Blackwood]

back to the origin, why not dive 60% if available and max depth floor of 53'

Floor depth aside, what's the average teaching depth?

If 53', you're going to run your CNS clock down right quick.



I'm perplexed by this thread. You suggest from the onset that it's a rhetorical question, and later admit that 60% was arbitrary, and yet you add parameters increasing the specificity of the question. Very strange.

Are you asking in abstract why instructors don't always dive "best mix?" If so, that would have been a much easier way to word it