Hydro Atlantic Incident 9-30-2012

[scubacouple]

I did a Deep Certification in Cozumel this July. As earlier noted, the markings in Coz can be less than obvious to the untrained. I went to 130' on air. Obviously the MOD for either 32% EAN or 36% EAN would have been exceeded on a 130' dive. You can be assured I tested my mix for 20.9%. Playing the "what ifs" though... Worst (likely) case scenario without any unforeseen circumstances: I'm diving a larger tank say a steel 120, as several Coz ops do, I'm not Nitrox trained, I get a poorly marked tank of 36% EAN. I go to 130' with an aggressive computer believing I'm diving air.. .

My actual dive was on an 80 with only 7 minutes planned at 130', but a steady ascent within NDL's gave me plenty of time beyond the Nitrox MOD. It's plausible but unlikely, as many accidents are. I still test every tank for CO and O2.

At 130fsw on 32% EAN you would not have exceeded your MOD @1.6 which is 132. I often use that blend for 130fsw dives and have for around 15 years. 130fsw-ish Wrecks though not certain deep ledges for lobster i know I'll be crawling the bottom the entire dive. At 36% you would have exceeded your MOD which is 114fsw @ 1.6. Then you become a "test" diver and no one really knows what will happen. I got that from flying. I was taught if you stay within the parameters of your POH the aircraft will perform to these specs in the POH. If you decide to go outside those parameters you become a test pilot... so true as with diving. Stay inside the numbers and they are pretty darn safe. Go outside them you roll the dice. nothing is guaranteed though. If you want 100% guarantees you best watch diving programs from your couch.

 

[boulderjohn]

Here's my immediate question: does any of this matter to a recreational diver (my wife and I) than don't go any deeper than 40' - 60' ? Added caveat: we have dived, and hope to continue to dive, in various parts of the world.

As far as nitrox is concerned, if an OW diver going to 40-60 feet accidentally got a tank of nitrox filled to the maximum allowed for recreational diving, which is incredibly unlikely, they would almost certainly finish the dive without a problem. The maximum percentage allowed for recreational diving is 40%, and using a percentage that high is extremely rare. In comparison, technical divers regularly do extended decompression stops at 70 feet using 50%. So, while it is always wise to be careful and safe, I would bet everything I own that no recreational diver going to 40-60 feet has ever had a problem with a mix-up on a tank of recreational nitrox.

Although CO can possibly be a problem, and the wise diver will be careful there, too, the actual occurrence of high CO levels in tanks is very rare, and you would be extremely unlucky to run into that sort of problem, too.

 

[DandyDon]

I haven't made a regimen of testing my tanks for CO, but it's not a bad idea. However, I do avoid PP blending like the plague. Blended or membrane for me. I haven't had a problem since.

I remember your incident and I believe I suggested your symptoms were similar to some CO toxicity symptoms. I was not clear on how CO was produced within your tanks, but adding O2 under pressure with the accompanying heating does sound like a possible source; thanks for explaining that way. The chance of getting a CO tainted tank from a straight air compressor still exist tho, and after your hit - I am surprised you're not testing. I know you are far & away much more accomplished diver than I will ever hope to be, but then old habits need to be changed at times. It's only 30 seconds/tank, Pete.

I'm not sure what the laws are in the UK but I'd be very surprised if they were any more lax than the US. The only bad fill I ever heard of in the UK was when there was too much water in the tank.

Getting CO in a tank is extremely easy, especially in urban areas or anywhere close to traffic. I saw a compressor installed on a private island here in Belize, and it wasn't a budget operation. The diesel motor was completely separated from the compressor and in another building. Nonetheless they didn't sufficiently allow for changes in wind direction, and under certain wind conditions the exhaust could be smelled across the entire island. The only way to overcome that problem was check prevailing air quality and only pump when it was adequate. I have stood on a dock here, one housing a big compressor, and smelled diesel exhaust wafting over from the next dock. They adopt the same precaution. My own electric-powered compressors were housed in the middle of a field some 30yds from the nearest road, and most passing traffic was electric golf carts anyway. Nonetheless I could occasionally smell exhaust. The Bauer triple filter system I used, the best in the business, is not capable of filtering out CO - you have to ensure it doesn't get in there in the first place. It is not an easy problem to deal with.

IIRC, UK requirements are far stricter than ours: 3 ppm max. I do not know if their enforcement is any better than ours tho.

The rest of your post misses an all too common source of CO tho: hot, busy compressors partially burning their own lubricating oils internally. Doesn't matter how clean your intake is and being electric doesn't help there. Somewhat less likely in the UK than Belize with the lower air temperature differences.

DanVolker: I am (reading this thread and not nitrox certified). It's hard for me to understand what is being said. I THINK that there are a couple of considerations:

1) If you dive Nitrox then you better not go below a certain depth or you risk Oxygen poisoning.
2) CO can get into regular air tanks as they are being filled (e.g. the blow-by of another compressor).
3) You can check your tank before jumping in. (I don't recall ever seeing anyone do this on a dive boat or in the shop, maybe I just wasn't aware.)

Can someone tell me if I am understanding?

Here's my immediate question: does any of this matter to a recreational diver (my wife and I) than don't go any deeper than 40' - 60' ? Added caveat: we have dived, and hope to continue to dive, in various parts of the world.

1: Nitrox & depth: That's partially true, yes. There is more to it which you'll learn when you get to that class, but I'd say that's the main factor.
2: Correct, CO can come from tainted air at the intake - as Peter described, or be produced by a hot compressor internally - as I explained, or in NetDoc's case, it was adding pure O2 to partially full tanks that seemed to have contained oil residue - with tanks heating as filled, the O2 & oil partially combusting. Only in recent years have we been able to test in the ppm range and test to be sure, rather than just trying & hoping.
3: Correct. Portable tank testers/analyzers are available, small & easy to carry, some water resistant in case splashed or dropped in a rinse bucket, and can give accurate results in 30 seconds. You probably haven't noticed divers testing their Nitrox as you just haven't gotten to that kind of diving yet. Still, not a bad idea to check Air tanks to be sure a Nitrox tank didn't get mixed in by mistake - a rare occurrence that some of us have seen. Testing for CO is still new and just not common yet.

 

[danvolker]

DanVolker: I am (reading this thread and not nitrox certified). It's hard for me to understand what is being said. I THINK that there are a couple of considerations:

1) If you dive Nitrox then you better not go below a certain depth or you risk Oxygen poisoning.
2) CO can get into regular air tanks as they are being filled (e.g. the blow-by of another compressor).
3) You can check your tank before jumping in. (I don't recall ever seeing anyone do this on a dive boat or in the shop, maybe I just wasn't aware.)

Can someone tell me if I am understanding?

Here's my immediate question: does any of this matter to a recreational diver (my wife and I) than don't go any deeper than 40' - 60' ? Added caveat: we have dived, and hope to continue to dive, in various parts of the world.

Thanks,

Bill

If there are no tech divers on the boat, meaning no chance of some silly 80/20 mix in a 80 cu ft scuba tank, then there is practically no way you could experience O2 toxicity on a 60 foot or shallower dive....
Even with tech divers aboard, your getting one of their tanks would be horrifyingly neligent on their part...though each diver ( including you) should take some responsibilty for any tank they/you decide to breathe out of...

The CO issue had zero do do with the death on the hydroatlantic wreck.....this was one of those tangents scubaboard tends to spin into. If you dive in the US, I would expect being struck by lightning to be a much greater risk than the CO i your tanks...particularly if you stay away from shops that look they are going out of business.

 

[Slamfire]

36% at 155 for 23 minutes?

That is a PO2 of 2.05 ata

The 1991 NOAA and the 1956 USN Oxygen Exceptional Exposure Limits for Nitrogen-Oxygen Mixed Gas Diving allows for 30 minutes at 2.0 ppO2. I'm not saying that this is justification for breaking the 1.4 limit that the industry has established. However, I would not be surprised if it ends up being discovered that there were other additional contributing factors in this death.

 

[dumpsterDiver]

The bottom is alot more than 155 ft...I think it is like 175 or so, if I recall from maybe 14 yrs ago?

 

[HowardE]

The 1991 NOAA and the 1956 USN Oxygen Exceptional Exposure Limits for Nitrogen-Oxygen Mixed Gas Diving allows for 30 minutes at 2.0 ppO2. I'm not saying that this is justification for breaking the 1.4 limit that the industry has established. However, I would not be surprised if it ends up being discovered that there were other additional contributing factors in this death.

The "Oxygen Clock" is really for pulmonary oxygen toxicity, not CNS oxygen toxicity. The name is misleading.

The wreck is 155 to the deck. 178 ish to sand.

CNS ox tox is increasingly more possible at po2 over 1.6 with time, exposure level, and workload. If the diver was at 170 for any time then his exposure was much higher than 2.0. That is if the mix was actually 36% what if it was higher even? The direct correlation to time and exposure isn't exactly known, but let's say the mix was actually 37% and the depth was 170. That is a PO2 of 2.28. Obviously in this case, without an actual analysis of the tanks, and the details from the dive computer, we won't really know exactly what the profile or breathing mixture was.

Sent from my SCH-I510 using Tapatalk 2

 

[Ayisha]

The 1991 NOAA and the 1956 USN Oxygen Exceptional Exposure Limits for Nitrogen-Oxygen Mixed Gas Diving allows for 30 minutes at 2.0 ppO2. I'm not saying that this is justification for breaking the 1.4 limit that the industry has established. However, I would not be surprised if it ends up being discovered that there were other additional contributing factors in this death.

And yet there was an OxTox and fatality here in Ontario two years ago with a PPO2 of 1.49 for about 4 minutes at depth (max of 145 feet), which made little sense. Many people use a PPO2 of 1.4 and issues are usually a function of time at depth, and the time was short. There's no magic number for anyone on any given day.

Something many people learned from that accident investigation which isn't made clear in some Enriched Air Nitrox or Rescue courses is that if someone is having a seizure of any kind, the rescuer needs to wait for the victim to stop seizing before beginning the ascent. During the tonic-clonic phase of a seizure, the glottis may close and air may not escape from the lungs during an ascent, and this can cause a lung overexpansion injury or embolism that may result in death.

http://www.underwatercouncil.com/downloads/incident_reports/ouc_2010_scuba_incident_reports.pdf

 

[danvolker]

The "Oxygen Clock" is really for pulmonary oxygen toxicity, not CNS oxygen toxicity. The name is misleading.

The wreck is 155 to the deck. 178 ish to sand.

CNS ox tox is increasingly more possible at po2 over 1.6 with time, exposure level, and workload. If the diver was at 170 for any time then his exposure was much higher than 2.0. That is if the mix was actually 36% what if it was higher even? The direct correlation to time and exposure isn't exactly known, but let's say the mix was actually 37% and the depth was 170. That is a PO2 of 2.28. Obviously in this case, without an actual analysis of the tanks, and the details from the dive computer, we won't really know exactly what the profile or breathing mixture was.

Sent from my SCH-I510 using Tapatalk 2

And in perspective...back in the early 90's, many of us routinely did AIR DIVES to 280 feet deep. We were "well over" the PO2 levels people are now suggesting as likely to be fatal. We did this because in the old days, we did not know what we know now. Also, Helium use was only found in the military....George Irvine and my WKPP buddies fixed this for us, around 1996, with our own WKPP Trimix tables, adjusted to an individual's VO2 Max score....Which we believed would correlate well to off-gassing by perfusion in the body...the results of peripheral adaptations to intense cardiovascular training and neo-vascularization.

My point is that many factors would probably need to come into play for a level like PO2 of 2.28 to kill. One could be the individual's unique genetic potential...another could be CO2 levels being created by workload at depth--this dramatically increasing Oxygen toxicity potentials on the dive if high workloads are experienced by the diver.....another could be levels of free radical scavengers at the cellular level--one belief is an enzymatic shutdown is occurring with Ox tox, and that high levels of Vitamin C and E and other free radical removers, can significantly effect the amount of PO2 exposure a diver could endure, prior to a tox event. This could mean general diet and vitamins taken, and it could even mean that being out late the previous evening, and drinking or generally building up free radicals, could have a very bad effect on the following day's dive, if high PO2 levels are going to be reached.

For general health, I see it as smart to take plenty of Vitamin C and E ( high gamma E, not the alpha toc junk), and Astaxanthin whenever I am diving ( we always use Nitrox except at BHB) . Why allow random oxidation increases from Nitrox to cause more free radicals to be floating around in your body...when this is easy to prevent.

 

[HowardE]

And in perspective...back in the early 90's, many of us routinely did AIR DIVES to 280 feet deep. We were "well over" the PO2 levels people are now suggesting as likely to be fatal. We did this because in the old days, we did not know what we know now. Also, Helium use was only found in the military....George Irvine and my WKPP buddies fixed this for us, around 1996, with our own WKPP Trimix tables, adjusted to an individual's VO2 Max score....Which we believed would correlate well to off-gassing by perfusion in the body...the results of peripheral adaptations to intense cardiovascular training and neo-vascularization.

My point is that many factors would probably need to come into play for a level like PO2 of 2.28 to kill. One could be the individual's unique genetic potential...another could be CO2 levels being created by workload at depth--this dramatically increasing Oxygen toxicity potentials on the dive if high workloads are experienced by the diver.....another could be levels of free radical scavengers at the cellular level--one belief is an enzymatic shutdown is occurring with Ox tox, and that high levels of Vitamin C and E and other free radical removers, can significantly effect the amount of PO2 exposure a diver could endure, prior to a tox event. This could mean general diet and vitamins taken, and it could even mean that being out late the previous evening, and drinking or generally building up free radicals, could have a very bad effect on the following day's dive, if high PO2 levels are going to be reached.

For general health, I see it as smart to take plenty of Vitamin C and E ( high gamma E, not the alpha toc junk), and Astaxanthin whenever I am diving ( we always use Nitrox except at BHB) . Why allow random oxidation increases from Nitrox to cause more free radicals to be floating around in your body...when this is easy to prevent.

Anecdotally... Another part of the 2.0 PO2 is as my associate tells people regarding his commercial diver training. They did a PO2 tolerance test. Candidates were put in the chamber and taken to 2 ATA on 100% O2. If the candidate could handle 30 minutes without toxing, then they could be commercial divers. He doesn't think this practice is still done.

As you stated... Workload I believe is a big part of the equation.

Additionally, some people believe that "work up" dives can acclimate a body to higher PO2 and additionally more adaptation to narcosis effects at greater depths. I bet when you guys were doing routinely deep air dives, that you worked up to it, and progressively pushed the limits rather than going full bore. Yes?