Enriched Air

[DCBC]

... some experienced scuba divers were routinely diving to 300'+ on air with little or no problem not so long ago. Guy

Hi Guy,

I've made a relatively short dive to 250 FSW on air when I was with the Navy. I had a difficult time sorting out direction and my O2 tolerance at that time was very high.

In 1993, Dr. Harabin did a statistical analysis on single-depth human exposures to 100-percent oxygen at pressure. The tests were undertaken at the U.S. Navy Experimental Diving Unit at Bethesda (U.S. Naval Medical Research Institute).

The bottom line was that the threshold for any symptom was 1.3 ATM and for convulsions it was 1.7 ATM PPO2.

I can't believe that recreational divers are diving over 300 FSW on air "with little or no problem." 300 FSW has a PPO2 over 2 ATM; which is a deadly dose.

I think that the world depth record for air was set in the 60's by Murray Black (a commercial diver), to a depth of 321 FSW. I understand that he survived, but had to be treated for pulmonary edema. I'm unaware if this has been surpassed.

 

[MXGratefulDiver]

I went to 154 on EAN25 once ... I was so loopy I couldn't think straight. Now anytime I'm going below about 120 I want some helium in my mix ...

... Bob (Grateful Diver)

 

[DCBC]

I went to 154 on EAN25 once ... I was so loopy I couldn't think straight. Now anytime I'm going below about 120 I want some helium in my mix ...

I understand a whole lot better now why you prefer diving shallow or going to Helium; good move.

 

[MaxBottomtime]

I think that the world depth record for air was set in the 60's by Murray Black (a commercial diver), to a depth of 321 FSW. I understand that he survived, but had to be treated for pulmonary edema. I'm unaware if this has been surpassed.

March 18 1994 - Dr Dan Manion, OC air record to 509 fsw
I had a buddy who routinely made 300' dives on air. His deepest was 400'.

 

[Guy Alcala]

March 18 1994 - Dr Dan Manion, OC air record to 509 fsw
I had a buddy who routinely made 300' dives on air. His deepest was 400'.

Bret Gilliam, in his book "Deep Diving", lists the record depths achieved in both caves and open water up to 1994, the pub. date (2nd. ed.) Manion's account of his record dive states that he had no memory of the dive at all; Gilliam considers that the real record depth should be 490 feet, which Manion did the previous day with no issues. Gilliam had previously held the record at 452 fsw (using a single HP100), and was able to do math and other problems on a slate at that depth.

The OC air record in the sixties increased progressively from 350 or so up to 440 fsw IIRR, usually set by very experienced cave divers (Tom Mount, Frank Martz, Jim Lockwood, Hal Watts, etc.) . Many of these same guys also held the cave depth records on air. Most of the individuals listed above were able to dive and work routinely on air at depths of 300' or more. But the fact is they were doing it regularly; For instance, Gilliam, in the year before his record dive, had done something like 650 dives with never more than a week's layoff, and had done multiple dives below 300'.

And when Exley and Bowden were preparing for their record attempt at 1,000 ffw in Zacaton cave, they were both prepping for it by doing air dives well below 300', as they were going to have ENDs of 330 feet or so if they reached max. depth. (1,080 ffw).

Guy Alcala

 

[Guy Alcala]

Hi Guy,

I've made a relatively short dive to 250 FSW on air when I was with the Navy. I had a difficult time sorting out direction and my O2 tolerance at that time was very high.

In 1993, Dr. Harabin did a statistical analysis on single-depth human exposures to 100-percent oxygen at pressure. The tests were undertaken at the U.S. Navy Experimental Diving Unit at Bethesda (U.S. Naval Medical Research Institute).

The bottom line was that the threshold for any symptom was 1.3 ATM and for convulsions it was 1.7 ATM PPO2.


My Nitrox class and IIRR the NOAA Diving Manual say 1.1 for symptoms, period, with no distinctions between the type of symptom and its threshold ppO2. I'll have to check what Rev. 6 of the USN Diving manual has to say.


I can't believe that recreational divers are diving over 300 FSW on air "with little or no problem." 300 FSW has a PPO2 over 2 ATM; which is a deadly dose.

I didn't say that they were doing it now (some may be still), just that it had been done in the past. With the widespread avilability of tri-mix there's little or no need (other than financial) to do so.


I think that the world depth record for air was set in the 60's by Murray Black (a commercial diver), to a depth of 321 FSW. I understand that he survived, but had to be treated for pulmonary edema. I'm unaware if this has been surpassed.

See MaxBT's and my posts for that info.

Guy

 

[Guy Alcala]

I went to 154 on EAN25 once ... I was so loopy I couldn't think straight. Now anytime I'm going below about 120 I want some helium in my mix ...

... Bob (Grateful Diver)

With my deepest dive to date being just 138 feet I'm not in any position to say just what my limit is. At that depth, on two occasions, I've had no or insignificant noticeable impairment. The impairment was minor dexterity or maybe coordination issues while doing a basic narc test: Counting down from 5 to 1 and then back up again with the fingers of one hand while flipping the hand over from front to back between each number. Of course, I sometimes have trouble completing that test properly at the surface, so I don't know if I was actually impaired or just off on that occasion

Other than that, I have never noticed any of the symptoms of narcosis on any dive I've done, despite routinely diving in cold water with limited visibility; indeed, those dives to 138' were done partly to see if I COULD experience some noticeable narcosis. I don't know if my tolerance is better than average (maybe because I'm used to operating while mildly hypoxic at altitude?), if I'm just not that imaginative or if I'm well-enough informed about narcosis and its effects (see the Mount-Milner experiment) that I'm able to function pretty well. But I've never been deep enough to hit a limit, although I'm gradually working my way down in 10' steps to try and find it. Of course, just because my limit is 'x' on one day it may be 'y' on some other, but at least I'll have some idea.

Guy

 

[The Chairman]

Other than that, I have never noticed any of the symptoms of narcosis on any dive I've done,

I emboldened the most important part of your entire post. Nitrogen Narcosis is a silent killer: you very rarely feel it's onset. I can guarantee that if you are below 80 fsw, you are impaired. You may not know it, you may even vehemently deny it, but you are impaired.

That doesn't mean you can't dive safely to 130 or even deeper. Planning, forethought, contingencies and bail out should be done ahead of time. Turn times, pressures and depths should be written down and adhered to. All of us think we are the exception and that's just plain denial mixed with hubris. You can manage narcosis to a degree, but you can never eliminate it.

From my experience, it is a mood/character amplifier. The timid become frightful, the confident become arrogant, the apathetic become morbidly so. That's why so few feel it. But everyone that I have tested has suffered from perceptual narrowing. You focus so intently on one task that you lose your situational awareness.

The most dangerous diver is the one who denies they are narced. The most foolish diver is the one who follows him.

 

[Papa_Bear]

I don't ever remember advocating anything dangerous having to do with diving so I resent anyone saying so! Next a wise diver told me once when they start bragging about how deep run for the door! I agree diving is NOT a macho activity and should never be portrayed as one! Deep diving will get you killed as a recreational diver! If you not one then state it and brag to someone who cares! My brother-in-law has video of him at 1700ft while in the Navy turning valves and working! But he won't dive as a recreational diver, go figure, but deep doesn't mean a thing! Basic is just that!

 

[bleeb]

Nitrogen Narcosis is a silent killer: you very rarely feel it's onset. I can guarantee that if you are below 80 fsw, you are impaired. You may not know it, you may even vehemently deny it, but you are impaired.

[...]

The most dangerous diver is the one who denies they are narced. The most foolish diver is the one who follows him.

In an alcohol safety lecture way back when, I remember a police officer quoting a saying that has stuck with me ever since: "The person LEAST able to tell if he's intoxicated is the one who's drunk." There's a bit of poetic license in that, but if someone's intellectual capacity is somehow impaired, it's not unreasonable to assume that their capacity to use the same abilities to recognize that impairment may also be somewhat decreased. And that probably applies to narcosis as much as it does to alcohol, even if the details may be slightly different.