Is this video real? 293ft on air...

[Akimbo]

You guys that keep putting down the Air 2. I'll bet it doesn't breath much different at 293 ft than it does at 120 or at 5 ft…

That is a loosing bet for almost any Scuba regulator. Combo inflators generally under-perform primary regulators, but not by orders of magnitude like many statements imply. A lot of the first generation combos were pretty poor and the distinction has been hard to shake:

Better Alternatives | Scuba Diving Magazine

…I've used mine at 120 and it breathes the same there as it does at the surface. Not great, but it will get me to the surface, which is it's entire purpose when I have to put it in my mouth because someone has an OOA situation.

Dive Lab tests on their ANSTI breathing simulator indicate it does not breath the same. However I have no doubt that you, and most other mortals, could not detect the difference. IMHO, you are absolutely correct that it is suitable for your application.

So what's the point? Accurate statements are critical to valid conclusions. I hated to see your most important statement picked apart by dueling statistics.

 

[vladimir]

I've never been diving in the tropics to have any experience but the water looks really bright to be almost 300 feet down.

To put the visibility thing in perspective, imagine looking from one end of a football field to the other through clear water on a sunny day. I think it should be pretty easy to imagine that there will be plenty of light to see.

I suppose that puts the distance in perspective--for football fans, anyway--but for the analogy to hold the field would have to be lit only from the home end zone, with no light from above, and you'd be assessing the light level at the visitor's end.

 

[Doc Harry]

I wonder if you could use a Spare Air at 293 feet?

 

[vladimir]

I wonder if you could use a Spare Air at 293 feet?

Sure...as a hammer, or to get you up to 270 feet to start your free ascent.

 

[Thalassamania]

Let's get beyond the confusion over "scientific diving community" and "science community" which I will agree was an unfortunate confusion that I contributed to.

My points were:

1. I agree, if you have an oxtox on O/C your chances of survival are slim.
2. I feel that your use of oxtox incidents from a Navy report, coupled with the statement: "The mortality for oxygen induced seizures with open circuit SCUBA at depths greater than 150 is very high ..." is misleading because of the arbitrary choice of 150 feet, you could have as easily said, "The mortality for oxygen induced seizures with open circuit SCUBA at depths greater than 30 is very high ..." which would have been equally true and even more misleading. By the way, were all those USN incidents on O/C? Would you please provide details and references?
3. Yet you state that: "... it is exceedingly rare to see an oxygen induced seizure occur with a ppo2 less than 1.6 (regardless of duration of exposure)." 1.6 is equivalent to about 220 ft, so don't you think that it might have been more intellectually honest to point that out rather than to have those divers who are slightly more arithmetically challenged than you are be left with the impression that the problem with oxtox on air starts at 150 feet?
4. In the range down to 190 feet which represents a ppO2 of about 1.4 ATA, we (the SCIENTIFIC DIVING COMMUNITY) have never experienced an oxtox event.
5. For that matter, even if you extend it to the broader SCIENCE COMMUNITY, we have never experienced an oxtox event whilst diving air.
6. You later go on to lay a fatality at the door of the science community that resulted from a diver's incompetence during a gas switch, because that diver was: a NOAA research diver (which is credential that means nothing more than a recreational open water diver); and a commercial diver (which only means that he comes from a community with a long tradition of having a level of risk two orders of magnitude greater than that of the SCIENTIFIC DIVING COMMUNITY). This has nothing what-so-ever to do with diving deep air, per se.
7. You then go on to discuss yet another case of diver incompetence in gas switching, that also has nothing to do with deep air.

If you are hurt because I have included a NOAA diver with many years of commercial diving in the SCIENTIFIC COMMUNITY, your need to get a thicker skin. If you can't handle someone saying your wrong, you need to grow up. Go back and read the posts and quit pettifogging!

I am not hurt, the entire SCIENTIFIC DIVING COMMUNITY is hurt. We spent a decade of our lives and in excess of 5 million dollars freeing ourselves from the confines of the OSHA commercial diving regulations. One of the things that we had to do was to go through each and every purported "scientific" accident that OSHA dredged up and demonstrate how they were not, in fact, part of our community. This included a number of bizarre accidents, like the thief who stole an early Beckman Electo-lung and died testing it out, a number of accidents that involved NOAA divers, and some well-meaning folks like yourself, who were self styled, "Marine Scientists" which OSHA initially took to mean the same thing as being part-and-parcel of the SCIENTIFIC DIVING COMMUNITY. So whilst you might consider it to be pettifogging, most of us see it as jealously guarding our real safety record.

 

[diverdoug1]

The reason I used the depth of 150' in my example is because depth greater than 150' is the depth noted in the source I used (USN Diving Medicine Syllabus - 2004 ed. Distribution American College of Hyperbaric Physicians). Yes, all the divers in this sample were all on open circuit. I did not lay a fatality at the doorstep of any community. That was your doing. Also, You stated that there had never been a fatality in the scientific community due to an oxygen toxicity seizure. That was an incorrect statement. You took issue with me pointing out your incorrect statement. You have further tried to "blow smoke" about OSHA regs. and about which subsets of divers have had problems with this issue with which gas mix (none of which was germaine to the conversation). You made a mistake when you said "your statment is missleading, since there has never been a single such occurance in the science community" I never implied this was on air/ trimix/ heliox/ or Kryptonite. I also never implied this was a certified scientific diver. If you think my statement is misleading, that's fine, but the pretense you give for calling it misleading is false. You were mistaken, and if you have a problem admitting it, that is fine too. I assume you are an adult, and can decide if you want to have the integrity to admit when you made an error.

 

[Rockhead]

You guys divers or lawyers?

 

[Thalassamania]

You guys divers or lawyers?

It was a very important legal issue that sensitized us to this particular definitional issue.

Doug, how do you explain the difference between your source and your statement: "... it is exceedingly rare to see an oxygen induced seizure occur with a ppo2 less than 1.6 (regardless of duration of exposure)."

I've already apologized and taken responsibility for confusing you, the "Marine Scientist," with a shorthand that would not have confused any member of the Scientific Diving Community.

 

[diverdoug1]

It was a very important legal issue that sensitized us to this particular definitional issue.

Doug, how do you explain the difference between your source and your statement: "... it is exceedingly rare to see an oxygen induced seizure occur with a ppo2 less than 1.6 (regardless of duration of exposure)."

I've already apologized and taken responsibility for confusing you, the "Marine Scientist," with a shorthand that would not have confused any member of the Scientific Diving Community.

You seem to be the one who is confused. Let me see if I can explain this so you might grasp the concept a little better. It is very rare to see an oxygen induced seizure at a partial pressure of 1.6 or lower (they are rare at even higher partial pressures of oxygen, I frequently treat patients with ppo2 greater than 2.0, and very rarely see a seizure in the chamber). The risk is much higher but still small. ALSO, when a diver has an oxygen induced seizure when he is under water, he is likely to drown. This statement is supported by the source I quote. I see no conflict between these two statements, but please explain. Also, if you wish to expunge your mistake by calling it "shorthand" that's great! (maybe you could tell us about the scientific diver secret handshake while you are at it---the rest of us in the scientific community would love to know)

 

[Thalassamania]

I do not wish to "expunge" the mistake, I want to take responsibility for it and applogize, which I did and to correct any misunderstanding concerning exactly what I was saying, which I also did. Now with that out of the way ... permit us, please, to now deal with the content.

I do disagree that any oxtox event on O/C is likely a fatal event.

Knowing what I do about physiology and about accident reporting, I rather doubt that any of the events that were reported by the Navy were anywhere near 150 feet on air ... I suspect that they where either much deeper (which by Navy protocols makes it rather unlikely that they were O/C, since SS and CCR are the preferred modes below 130). So something in that tale doesn't smell quite right and I think it warrants further investigation. Face it, the USN Diving Medicine Syllabus is not exactly a carefully refereed publication.

Within the Scientific Diving Community there has never been a case of oxtox on open circuit air scuba. As far as I know, within the entire science community there has never been a case of oxtox on open circuit air scuba above 190. I suspect that, in point of fact, there has never been a case of oxtox on open circuit air scuba above 190, period.

So whilst an oxtox event would likely kill you, the actual odds of dying approach zero, making an O/C circuit dive on air to 190 rather risk free, at least from the perspective of oxygen toxicity.