Could be her nerves now from scaring herself and her brother ragging on her lol
Accidental DECO and mild panic in a non tech certified diver.
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divinh
Contributor
I had recently dove with someone who questioned why I sometimes hover over everyone else. I explained that I was doing consecutive multi-day diving and wanted to stay within NDL. I had already done two weeks before this guy's arrival to the dive op. He told me that I didn't need to worry and that after 12 hrs of surface time, there would be no problem. Well, the very next day, when we reached our safety stop, the guide flashed three minutes. I flashed back three in agreement. The guy flashed back four! The guide looked at his dive computer and saw that he had accrued four minutes of deco. I waited out the three minutes with another diver who had no dive computer and we surfaced together after the guide signaled for us to do so. The guide hung with the guy for the 4 min deco plus 3 min safety.
I think he's been lucky that all his previous dives have probably been with people who were air constrained and not NDL constrained. And this was another case of not watching the dive computer nor knowing the difference between mandatory deco stop versus safety stop because he didn't notice that four minutes was out-of-the-norm.
I think he's been lucky that all his previous dives have probably been with people who were air constrained and not NDL constrained. And this was another case of not watching the dive computer nor knowing the difference between mandatory deco stop versus safety stop because he didn't notice that four minutes was out-of-the-norm.
Could also have been the setting on his computer. That said, he still wasn't watching it properly.
I think a measure of sense should be applied.
A mistake was made, corrective action was taken at the time. No one got hurt (other than their pride). Those involved have asked sensible questions, and generally received sensible answers.
The fact that the questions where asked indicates those involved accept
a. mistakes where made.
BUT, most importantly,
b. they wish to learn from them.
If the general response is a roasting, then people will cover up mistakes and poor practice.
We should learn from the aerospace industry.
Incidents are logged, analysed, and lessons learned.
As a general rule, they are viewed as failures of the system, rather than individuals.
Finger pointing is generally counter productive.
There are NONE who dive regularly who have not at some time done foolish things.
As an instructor and experienced(?) diver, I try to pass on good advice, and hope that the lessons I've learnt, sometimes through stupidity, are passed to those I dive with. Hopefully, they will learn from my mistakes, and avoid the errors I've made. I accept, that human nature means, people sometimes need to learn for themselves. I hope, that what I have taught them will help them get out of the water in one piece, when they do do something stupid.
I also accept that some of the lessons we've learnt have been costly, I've lost friends, sometimes they made a mistake, sometimes they where unlucky. What is often frustrating, is seeing people breaking hard learnt rules, through ignorance, or a sense of superiority.
A mistake was made, corrective action was taken at the time. No one got hurt (other than their pride). Those involved have asked sensible questions, and generally received sensible answers.
The fact that the questions where asked indicates those involved accept
a. mistakes where made.
BUT, most importantly,
b. they wish to learn from them.
If the general response is a roasting, then people will cover up mistakes and poor practice.
We should learn from the aerospace industry.
Incidents are logged, analysed, and lessons learned.
As a general rule, they are viewed as failures of the system, rather than individuals.
Finger pointing is generally counter productive.
There are NONE who dive regularly who have not at some time done foolish things.
As an instructor and experienced(?) diver, I try to pass on good advice, and hope that the lessons I've learnt, sometimes through stupidity, are passed to those I dive with. Hopefully, they will learn from my mistakes, and avoid the errors I've made. I accept, that human nature means, people sometimes need to learn for themselves. I hope, that what I have taught them will help them get out of the water in one piece, when they do do something stupid.
I also accept that some of the lessons we've learnt have been costly, I've lost friends, sometimes they made a mistake, sometimes they where unlucky. What is often frustrating, is seeing people breaking hard learnt rules, through ignorance, or a sense of superiority.
This is an incorrect believe.
There is plenty of research data to state that the risk of a CNS incident when breathing PO2's of 1.6 and above are a credible risk. Both the Royal Navy and the United States Navy have research data on this. The most notable issue is the huge variability of tolerance. Both between individuals. But of more concern, is that the same individual may demonstrate a high tolerance on one series of dives, then repeat the dive later and demonstrate an extremely low tolerance, this in a controlled enviroment.
A quick google and you get his from DAN :-
During a nitrox dive done at Duke University's F.G. Hall Hypo/Hyperbaric Center at 100 feet / 30 meters, breathing 1.6 ata pO2 (oxygen partial pressure) during heavy exercise, a convulsion occurred after 40 minutes. Perhaps this would not have occurred had there been a lower level of exercise, but it does seem to indicate that the NOAA limit of 45 minutes for 1.6 ata nitrox diving is not overly conservative.
Breathing 100 percent oxygen during the 20-foot / 6.1-meter decompression stop is common practice, and at this depth, the partial pressure will be about 1.6 ata. At this shallow depth, under conditions of rest, the chance of CNS oxygen toxicity should be very low. But, like most things in life, this is not certain, as evidenced by a recently reported oxygen convulsion at 20 feet / 6.1 meters during decompression by a technical diver after completing a dive on the Lusitania.
Breathing 100 percent oxygen during the 20-foot / 6.1-meter decompression stop is common practice, and at this depth, the partial pressure will be about 1.6 ata. At this shallow depth, under conditions of rest, the chance of CNS oxygen toxicity should be very low. But, like most things in life, this is not certain, as evidenced by a recently reported oxygen convulsion at 20 feet / 6.1 meters during decompression by a technical diver after completing a dive on the Lusitania.
There was no comment on if the Duke incident was dry (in a chamber), or wet. We know that when immersed, tolerances are significantly lower than when dry (i.e. in a hyperbaric chamber).
Caveeagle
Contributor
For those of you who advocate matching your computer to buddy’s air profile, I have a couple questions.
What if you have a lost buddy situation, or even a buddy that goes into unplanned deco with low gas reserves. In both cases, you would be in a better position to help if you were confident in your actual TTS.
Having a little more time to look for a lost buddy, or surfacing faster for help are both benefits.
Although I don’t tend to be a big proponent of solo diving, I am a fan of self sufficiency. The whole idea of diving with a buddy who cannot be trusted to track their own dive profile is a non-starter for me. I might dive with that person once or twice to try and help them, but beyond just being a helpful mentor, I won’t do any serious dive with someone who is a liability.
What if you have a lost buddy situation, or even a buddy that goes into unplanned deco with low gas reserves. In both cases, you would be in a better position to help if you were confident in your actual TTS.
Having a little more time to look for a lost buddy, or surfacing faster for help are both benefits.
Although I don’t tend to be a big proponent of solo diving, I am a fan of self sufficiency. The whole idea of diving with a buddy who cannot be trusted to track their own dive profile is a non-starter for me. I might dive with that person once or twice to try and help them, but beyond just being a helpful mentor, I won’t do any serious dive with someone who is a liability.
Thanks so much for finding and posting that article. That much being said, it's clear from the article -that shows only 1 relevant example- that the convulsions only occurred at a P02 of 1.6 after a dive of 40 minutes duration during which time there was heavy exercise during the entire dive. It's also not stated if the diver in the given example was using a single tank and a blend of at or less than 40% O2 (as per my stated parameters). Or- if it was a simulated dive in a chamber, as you suggested.
In the example cited, the diver HAD to be fairly deep and/or breathing a very rich EAN mix to get to, and maintain 1.6 for 40 minutes.
So I "might" need to clarify that there has "never been a documented case of an 02 hit on a single tank recreational (non tech) single tank diver breathing <40 percent 02 other than a test case where heavy exercise was done for 40 minutes and maintaining a 1.6 the entire time.
When a diver such as myself sets their dive computer for 1.6, it is highly unlikely that they would be diving diving 1.6 the entire dive- if they even get that high at all. It's just the upper limit. I don't think I EVER hit 1.6 during a dive.
The article says that P02 levels ABOVE 1.6 are a credible risk. And there is no other research data in that article other than the 1 example that addresses the parameters I stated (and again we don't know the 02 blend or if it was a single tank) which is what we are addressing here.
Not sure I follow your reasoning. On your point about a buddy going into unplanned deco. Surely by having your DC matched to theirs, there is less chance of this happening as you both have eyes on roughly the same NDL (hopefully). Regarding lost buddy scenario, you would be in exactly the same NDL situation if you were also diving air, the only difference being you have some (albeit unknown) additional padding.
Don't get me wrong, I am not advocating air setting for nitrox as a standard practice, but in this unusual scenario it could be an option. Ideally both divers would be diving the same gas and one wouldn't be reliant on the other for situational awareness, but unfortunately we don't live in an ideal world.
Maybe I was not clear enough in describing the scenario I mentioned. This would only be the case in an "instabuddy" type of dive in addition with different mixes and no planned deco. So something that, at least for my diving is quite unusual.
If diving with my usual buddies I know them good enough to trust that they take care of checking their computers and act reasonable.
Since during these "instabuddy" dives I usually apply the "search for one minute, then surface" method in case of lost buddy, I wont need a bigger time reserve to look for him/her. If the buddy goes into unplanned deco and my computer set on air, instead of nitrox, I would usually hang around with the buddy anyways and not clear my nitrox-deco and take off. Anyways, if my instabuddy does not check that he is heading into unplanned deco, I would notice it with my computer set to air, because I do frequently check it, and signal him, in order to avoid deco.
Of course, in doing so, in case of an incident, I would not know my exact remaining bottom time, or exact deco obligation, but I would know, that it is less then shown.
Disclaimer:
For any dives with planned deco or the chance to get into a longer unplanned deco, what I have stated before would not apply and I would of course have my computer set to my own mix.
I also dont want to advocate it and see this as the "default-option". But depending on the situation, gut feeling towards the buddy etc. it might be something I consider for the stated reason.
If diving with my usual buddies I know them good enough to trust that they take care of checking their computers and act reasonable.
Since during these "instabuddy" dives I usually apply the "search for one minute, then surface" method in case of lost buddy, I wont need a bigger time reserve to look for him/her. If the buddy goes into unplanned deco and my computer set on air, instead of nitrox, I would usually hang around with the buddy anyways and not clear my nitrox-deco and take off. Anyways, if my instabuddy does not check that he is heading into unplanned deco, I would notice it with my computer set to air, because I do frequently check it, and signal him, in order to avoid deco.
Of course, in doing so, in case of an incident, I would not know my exact remaining bottom time, or exact deco obligation, but I would know, that it is less then shown.
Disclaimer:
For any dives with planned deco or the chance to get into a longer unplanned deco, what I have stated before would not apply and I would of course have my computer set to my own mix.
I also dont want to advocate it and see this as the "default-option". But depending on the situation, gut feeling towards the buddy etc. it might be something I consider for the stated reason.
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