Another lesson learned today

spatman · Post by **spatman** » Mon Mar 26, 2012 9:27 pm

Alcohol and nitrogen affect different people in different ways. It's up to the individual to know their limits and susceptibility, and act responsibly.

kdupreez · Post by **kdupreez** » Mon Mar 26, 2012 9:32 pm

spatman wrote:Alcohol and nitrogen affect different people in different ways. It's up to the individual to know their limits and susceptibility, and act responsibly.

[sarcasm]Yup, and the alcohol limit by law is .08 because people are that responsible..[/sarcasm]

spatman · Post by **spatman** » Mon Mar 26, 2012 9:39 pm

I said act, not drive. And are you saying the that there should be legislation passed regarding nitrogen loading?

lamont · Post by **lamont** » Mon Mar 26, 2012 9:51 pm

spatman wrote: I own an analyzer and always check my own tanks. My question was whether there was any difference between analyzing my tanks the day I got them from the shop compared to the day of the dive, whether that was a couple days or a week or more.

If the tanks are hot and the O2 is hot there's a slight temperature dependency of the chemical reaction the O2 sensor uses, and I think I've noticed that my tanks are usually a bit higher O2 percentage measuring at the shop.

[EDIT: meh, megaphysicsbrainfart... adiabatic expansion will swamp that... i plead low glucose... time for dinner...]

If you are filling helium, particularly if you boost and slowly fill, then you can wind up with poorly mixed gases in the tank and the gas will need to diffuse properly before it reads correctly. There's probably a good analogy with creating layered mixed drinks that would go over with this crowd...

kdupreez · Post by **kdupreez** » Mon Mar 26, 2012 10:09 pm

Hahaha.. Hellz yea!! Scuba Police! No seriously Matt, I'm saying that people are just not that responsible, especially when it comes to physiological conditions that affect different people differently and even affect the same people differently in different environmental conditions..

If you say its OK to do it because you feel fine at 150 feet.. well, who defines what that "feeling ok" means? its very very very subjective, your feeling OK and my wife's feeling OK is very very different.. so I draw the line at 100ft where its known for a fact that people are narked..

I will typically not do a dive with a buddy below 100 feet on non-heluim mixes because I just dont know what he/she will feel like or how they will react due to narcosis at 120 feet when I run into an emergency.. again its all about stacking the odds in your favor within an environment that does not naturally sustain life..

Besides, its just the responsible thing to do to make sure you are in the best possible position to think clearly when your buddy will need you the most..

Btw, go read this research : http://archive.rubicon-foundation.org/x ... 56789/2199

Repetitive Narcosis studies on experienced divers over 5 days showed they felt "adapted" and a heck of a lot better and clearer and felt more capable on day 3 and thought they did better in tasks... But evidence showed there was no measurable improvement in spite of them thinking they were "adapted" to narcosis..

Great false sense of security about "what my limits and susceptibility" are if you feel better, yet your motor responses are not improved at all..

ljjames · Post by **ljjames** » Mon Mar 26, 2012 10:12 pm

Just to throw in a bit of a monkey wrench and fun in (and take it back to the O2 thread drift, because i think we were covering some good stuff and the narcosis thing has been beaten to death in about 600 different threads on 20 different forums over the past 15 years - it turns into a religion thing

When was the last time you (any of you) changed the Sensor in your O2 analyzer? When was the last time they changed the sensor in the local dive shop analyzer? How about battery? etc... how warm is the air in the shop when you calibrate? are you calibrating with dry (cold - expansion) air from a cylinder or just waving it around? Is the shop ambient air warm and humid and then the expansion causes condensation on your analyzer? All these things change how your sensor is going to read. I always consider it +/- 3% and call it good. That is always why you'll never hear me whining about a 31% mix when i brought it in for 32%. Based on who's analyzer

BUT, this is also why I analyze when i get to the site as well. In addition to the myriad of other reasons already posted, I am just generally curious how close my sensor reads to what it is I think I got. I've also fiddled around with voltage limited cells (my analyzer uses same sensors as meg) and cells that are acting funny and/or got wet, etc... (yes, I get bored at times and tinker) Do you know how to tell if your sensor is reaching end of its useful life? Do you know the voltage range your sensor should be reading at, at a specific % O2? Do you know if it's reading regularly high? low?

Joshua Smith · Post by **Joshua Smith** » Mon Mar 26, 2012 10:26 pm

I like to think there's some kind of middle ground between being totally care free, acting as if nothing bad can ever happen to me underwater, and treating routine shore dives at benign, well known sites like Muk and cove 2 like they were remote offshore exploration dives.

There are lots and lots of dives below 100' on air happening every day, and very, very few deaths. That said, I never exceed an END of 100 fsw on a tech dive, because its cheap and easy not to, and I need to be sharp for them.

In this case, I don't really see diving the boat at Muk without Helium as a serious threat to life and limb, for someone with a moderate amount of experience and skill. Navigation and some degree of gas planning are required skills, of course, but its not the frigging Brittanic.

I DO think diving with little or no understanding of what you and or your buddy is breathing is a huge mistake, though. That can kill you pretty damn fast no matter what your skill level is in other departments. And THAT mistake seems to have happened at 1ATA. Don't really see where Helium would have helped in this case, myself.

kdupreez · Post by **kdupreez** » Mon Mar 26, 2012 10:28 pm

ljjames wrote:Just to throw in a bit of a monkey wrench and fun in (and take it back to the O2 thread drift, because i think we were covering some good stuff and the narcosis thing has been beaten to death in about 600 different threads on 20 different forums over the past 15 years - it turns into a religion thing

Narcosis was very much a part of the entire thread and I actually do think that Narcosis is a very useful and important discussion to have and we should not discount it as "meh, been talked about alot so lets ignore it.."

I think new recreational divers on this forum who might not have seen the 600 other threads and could actually find the information useful.

Jeff Pack · Post by **Jeff Pack** » Mon Mar 26, 2012 10:30 pm

ljjames wrote:Just to throw in a bit of a monkey wrench and fun in (and take it back to the O2 thread drift, because i think we were covering some good stuff and the narcosis thing has been beaten to death in about 600 different threads on 20 different forums over the past 15 years - it turns into a religion thing

When was the last time you (any of you) changed the Sensor in your O2 analyzer? When was the last time they changed the sensor in the local dive shop analyzer? How about battery? etc... how warm is the air in the shop when you calibrate? are you calibrating with dry (cold - expansion) air from a cylinder or just waving it around? Is the shop ambient air warm and humid and then the expansion causes condensation on your analyzer? All these things change how your sensor is going to read. I always consider it +/- 3% and call it good. That is always why you'll never hear me whining about a 31% mix when i brought it in for 32%. Based on who's analyzer

BUT, this is also why I analyze when i get to the site as well. In addition to the myriad of other reasons already posted, I am just generally curious how close my sensor reads to what it is I think I got. I've also fiddled around with voltage limited cells (my analyzer uses same sensors as meg) and cells that are acting funny and/or got wet, etc... (yes, I get bored at times and tinker) Do you know how to tell if your sensor is reaching end of its useful life? Do you know the voltage range your sensor should be reading at, at a specific % O2? Do you know if it's reading regularly high? low?

Hmm, now you've got me thinking. How do you calibrate your O2 sensor and against what? I havent started mixing nitrox yet, but now you've got me thinking about it. Do sensors wear out, how often do you calibrate, and against what?

ljjames · Post by **ljjames** » Mon Mar 26, 2012 10:33 pm

To an experienced diver 100' swim around the logs may feel like a walk in the park. To someone with a mere handful of dives, fresh out of class, it might as well be the britannic. Its all a matter of perspective. When you've only just put your head underwater a few minutes before, the bottom of the pool is like 100'

Koos, all i'm saying is that the narcosis discussion too often becomes one of religion. You guys are already talking about driving drunk which generally means it's halfway there - i was trying to find a gentle way of encouraging it to not go that way. Of course it is a legitimate discussion. Narcosis and CO2 is a topic that i tend to beat 6 ways to sunday, simply because i have reasonably extensive experience on both sides of that coin and know that i like diving helium deeper than 100'. BUT, that is my personal preference.

kdupreez · Post by **kdupreez** » Mon Mar 26, 2012 10:34 pm

Joshua Smith wrote:..of course, but its not the frigging Brittanic.

Wuttttt ? Its not?? Those Deep air hallucinations be damned!!!!

All good points Josh and I'm certainly not the scuba police.. its my educated opinion that I stand by

A Tec dive to 140' somewhere exotic makes handling an emergency no less important than 140' at Mukilteo.. I'd like to be bell clear for both..

Joshua Smith · Post by **Joshua Smith** » Mon Mar 26, 2012 11:09 pm

kdupreez wrote:
Joshua Smith wrote:..of course, but its not the frigging Brittanic.
Wuttttt ? Its not?? Those Deep air hallucinations be damned!!!!

All good points Josh and I'm certainly not the scuba police.. its my educated opinion that I stand by

A Tec dive to 140' somewhere exotic makes handling an emergency no less important than 140' at Mukilteo.. I'd like to be bell clear for both..

Of course. And people can,and have, drowned in 4 inches of water, too. I'm just adding my own perspective. Like Laura was saying about new divers: my first dive to the I beams in cove 2 might as well have been the frigging Brittandrea Dorikulla. But with experience and repetition, it became a familar place. I probably could have handled an emergency reasonably well in my not so long ago early days, but I'm glad I didn't have to.

Joshua Smith · Post by **Joshua Smith** » Mon Mar 26, 2012 11:16 pm

Jeff Pack wrote:
ljjames wrote:Just to throw in a bit of a monkey wrench and fun in (and take it back to the O2 thread drift, because i think we were covering some good stuff and the narcosis thing has been beaten to death in about 600 different threads on 20 different forums over the past 15 years - it turns into a religion thing

When was the last time you (any of you) changed the Sensor in your O2 analyzer? When was the last time they changed the sensor in the local dive shop analyzer? How about battery? etc... how warm is the air in the shop when you calibrate? are you calibrating with dry (cold - expansion) air from a cylinder or just waving it around? Is the shop ambient air warm and humid and then the expansion causes condensation on your analyzer? All these things change how your sensor is going to read. I always consider it +/- 3% and call it good. That is always why you'll never hear me whining about a 31% mix when i brought it in for 32%. Based on who's analyzer

BUT, this is also why I analyze when i get to the site as well. In addition to the myriad of other reasons already posted, I am just generally curious how close my sensor reads to what it is I think I got. I've also fiddled around with voltage limited cells (my analyzer uses same sensors as meg) and cells that are acting funny and/or got wet, etc... (yes, I get bored at times and tinker) Do you know how to tell if your sensor is reaching end of its useful life? Do you know the voltage range your sensor should be reading at, at a specific % O2? Do you know if it's reading regularly high? low?
Hmm, now you've got me thinking. How do you calibrate your O2 sensor and against what? I havent started mixing nitrox yet, but now you've got me thinking about it. Do sensors wear out, how often do you calibrate, and against what?

Sensors do wear out. Callibration is quick and easy. A decent check at 1ATA is to verify in ambient air (20.9%) and then use a known source of 100% 02.

doublesunder · Post by **doublesunder** » Mon Mar 26, 2012 11:25 pm

There are many schools of thought on this subject. It is ultimately up to the Individual diver to research the information available, gain the necessary experience and training , then make an informed decision.

kdupreez · Post by **kdupreez** » Tue Mar 27, 2012 12:00 am

doublesunder wrote:There are many schools of thought on this subject. It is ultimately up to the Individual diver to research the information available, gain the necessary experience and training , then make an informed decision.

WTH - This is all brain washing dude, there is only ONE person that can be right..

No seriously, +11

I Totally agree with ya!

I'm not gonna force my opinion down anyone's throat but I will provide my position and motivate the rationale behind it when asked.

We should also not confuse new diver capacity with narcosis, two very different things. with experience and familiarity with equipment and the site and diving in general, increases capacity and this brings confidence and comfort.. but that aint curing narcosis..

airsix · Post by **airsix** » Tue Mar 27, 2012 8:28 am

kdupreez wrote: WTH - This is all brain washing dude, there is only ONE person that can be right.. penelope

Sometimes it's fun reading this forum on my phone just to see the emoticons replaced with people's names. It often reveals profound truths.

; )

LCF · Post by **LCF** » Tue Mar 27, 2012 8:41 am

Diving is always a risk assessment, whether one acknowledges that consciously or not. Just picking up equipment and going underwater is taking a risk, albeit a small one.

Decisions regarding END and EAD are also risk assessments, and people are going to come to different conclusions, depending on their risk tolerance. I think what is really important is that those decisions be as informed as possible. Looking at the chart in the GUE Tech 1 manual, which recapitulated the results from a whole bunch of studies of O2 toxicity, left me with the acute awareness that oxygen toxicity is EXTREMELY variable, both between subjects and in the same subject on different days. I found this quite disturbing, as survival from full blown ox-tox is almost vanishingly rare. A couple of years later, I read the horrible account of the death of a woman in a cave, at a 1.4 ppO2, and decided right then and there that 1.2 for bottom time made sense to me. Of course, I don't do the dives where making that decision is going to make my deco unsupportable or limit my bottom time to something that doesn't make it worth doing the dive. And that's kind of the problem with 125 foot dives as NO deco dives; you just don't get to be down there long enough to make it worthwhile to me.

Narcosis always degenerates into an argument, and I think a lot of that is due to two things. One is that uneventful dives require very little rapid or accurate processing, once you have the mechanics of diving relegated to your subconscious. Looking at the wreck or the fish is a pretty low-demand activity. Do several hundred uneventful dives, and you can become quite confident that you are just fine at whatever depth you're diving. And most of us, if we are careful and do some planning, have uneventful dives.

The second is that narcosis doesn't feel like being drunk, at least for me it doesn't. Drunk I recognize -- my balance is off, my speech is slurred, I drop things . . . I know what that feeling is. For me, at least, narcosis is just being dull. I've had two VERY vivid experiences while cave diving, where I looked at something and thought, "Huh, that's strange . . ." and swam on, making an error that, had my buddy not caught it (or, embarrassingly, my instructor in one of the cases -- since NONE of my two other buddies caught it, either) could have resulted in a life-threatening danger to all of us. I call it the "duuuuh" feeling, and I would like to think that next time, I would recognize it. But I don't think I would, because one of the characteristics of it is that you aren't sharp enough to realize you're dull. So instead, I have set personal limits for END -- AND I have made a decision about what limits I think are acceptable for my dive buddies. Although I may be limiting people with more narcosis tolerance than I have, that's okay with me. We all agree, or, if our risk tolerances are different, we should be diving with different buddies or doing different dives.

That's what it comes down to: Each of us makes decisions about the dive parameters that feel okay, and each dive we do should be a dive where all the people involved feel okay about doing it. People do all kinds of dives that I wouldn't -- I'm still afraid of rebreathers, but Josh takes one to scary dark depths on a regular basis, and so far has done fine doing that. Bob does solo technical dives, the thought of which gives me the willies, and he's surviving just fine, too. I don't disapprove or judge people who do what I won't; I just set my own limits, and dive them with people who don't mind following them, too.

CaptnJack · Post by **CaptnJack** » Tue Mar 27, 2012 8:43 am

airsix wrote:
kdupreez wrote: WTH - This is all brain washing dude, there is only ONE person that can be right.. penelope
Sometimes it's fun reading this forum on my phone just to see the emoticons replaced with people's names. It often reveals profound truths.

; )

Are you trying to tell me something?

:luv:

I analyze and label (or relabel as the case may be) my gases when I put the regs on. At the same time I put the tanks in the truck. Usually that's the night before. The day of any dive I don't want to feel rushed so I generally setup my gear the day beforehand and then its all analyzed and ready to go.

If I am somewhere remote I analyze and (re)label right before I put the regs on, whether that's the night before or the day of ends up being slightly more variable.

Norris · Post by **Norris** » Tue Mar 27, 2012 8:51 am

LCF wrote:Diving is always a risk assessment, whether one acknowledges that consciously or not. Just picking up equipment and going underwater is taking a risk, albeit a small one.

Decisions regarding END and EAD are also risk assessments, and people are going to come to different conclusions, depending on their risk tolerance. I think what is really important is that those decisions be as informed as possible. Looking at the chart in the GUE Tech 1 manual, which recapitulated the results from a whole bunch of studies of O2 toxicity, left me with the acute awareness that oxygen toxicity is EXTREMELY variable, both between subjects and in the same subject on different days. I found this quite disturbing, as survival from full blown ox-tox is almost vanishingly rare. A couple of years later, I read the horrible account of the death of a woman in a cave, at a 1.4 ppO2, and decided right then and there that 1.2 for bottom time made sense to me. Of course, I don't do the dives where making that decision is going to make my deco unsupportable or limit my bottom time to something that doesn't make it worth doing the dive. And that's kind of the problem with 125 foot dives as NO deco dives; you just don't get to be down there long enough to make it worthwhile to me.

Narcosis always degenerates into an argument, and I think a lot of that is due to two things. One is that uneventful dives require very little rapid or accurate processing, once you have the mechanics of diving relegated to your subconscious. Looking at the wreck or the fish is a pretty low-demand activity. Do several hundred uneventful dives, and you can become quite confident that you are just fine at whatever depth you're diving. And most of us, if we are careful and do some planning, have uneventful dives.

The second is that narcosis doesn't feel like being drunk, at least for me it doesn't. Drunk I recognize -- my balance is off, my speech is slurred, I drop things . . . I know what that feeling is. For me, at least, narcosis is just being dull. I've had two VERY vivid experiences while cave diving, where I looked at something and thought, "Huh, that's strange . . ." and swam on, making an error that, had my buddy not caught it (or, embarrassingly, my instructor in one of the cases -- since NONE of my two other buddies caught it, either) could have resulted in a life-threatening danger to all of us. I call it the "duuuuh" feeling, and I would like to think that next time, I would recognize it. But I don't think I would, because one of the characteristics of it is that you aren't sharp enough to realize you're dull. So instead, I have set personal limits for END -- AND I have made a decision about what limits I think are acceptable for my dive buddies. Although I may be limiting people with more narcosis tolerance than I have, that's okay with me. We all agree, or, if our risk tolerances are different, we should be diving with different buddies or doing different dives.

That's what it comes down to: Each of us makes decisions about the dive parameters that feel okay, and each dive we do should be a dive where all the people involved feel okay about doing it. People do all kinds of dives that I wouldn't -- I'm still afraid of rebreathers, but Josh takes one to scary dark depths on a regular basis, and so far has done fine doing that. Bob does solo technical dives, the thought of which gives me the willies, and he's surviving just fine, too. I don't disapprove or judge people who do what I won't; I just set my own limits, and dive them with people who don't mind following them, too.

kdupreez · Post by **kdupreez** » Tue Mar 27, 2012 9:02 am

LCF wrote:[ .. All that awesome stuff that Lynne said goes here .. ]

CaptnJack · Post by **CaptnJack** » Tue Mar 27, 2012 9:41 am

Joshua Smith wrote:In this case, I don't really see diving the boat at Muk without Helium as a serious threat to life and limb, for someone with a moderate amount of experience and skill. Navigation and some degree of gas planning are required skills, of course, but its not the frigging Brittanic.

I DO think diving with little or no understanding of what you and or your buddy is breathing is a huge mistake, though. That can kill you pretty damn fast no matter what your skill level is in other departments. And THAT mistake seems to have happened at 1ATA. Don't really see where Helium would have helped in this case, myself.

Totally agree, except for the Brittanic part. If you squint real hard everything becomes much bigger.

TWSS

limeyx · Post by **limeyx** » Tue Mar 27, 2012 12:54 pm

Joshua Smith wrote:
Sensors do wear out. Callibration is quick and easy. A decent check at 1ATA is to verify in ambient air (20.9%) and then use a known source of 100% 02.

Ahhhhh but how "known" is your known source ???? Maybe some shop-monkey slipped 21% Argon into the O2 supplies !!!
There are known unknowns and then there are unknown unknowns!

Joshua Smith · Post by **Joshua Smith** » Tue Mar 27, 2012 12:59 pm

limeyx wrote:
Joshua Smith wrote:
Sensors do wear out. Callibration is quick and easy. A decent check at 1ATA is to verify in ambient air (20.9%) and then use a known source of 100% 02.
Ahhhhh but how "known" is your known source ???? Maybe some shop-monkey slipped 21% Argon into the O2 supplies !!!
There are known unknowns and then there are unknown unknowns!

Damnit. Now I gotta buy an analyzer to verify my analyzer. Hmmmm- how can I verify my verification analyzer?

limeyx · Post by **limeyx** » Tue Mar 27, 2012 1:01 pm

Joshua Smith wrote:
limeyx wrote:
Joshua Smith wrote:
Sensors do wear out. Callibration is quick and easy. A decent check at 1ATA is to verify in ambient air (20.9%) and then use a known source of 100% 02.
Ahhhhh but how "known" is your known source ???? Maybe some shop-monkey slipped 21% Argon into the O2 supplies !!!
There are known unknowns and then there are unknown unknowns!
Damnit. Now I gotta buy an analyzer to verify my analyzer. Hmmmm- how can I verify my verification analyzer?

But then who verifies the verificator ? Tough issues !

Joshua Smith · Post by **Joshua Smith** » Tue Mar 27, 2012 1:04 pm

limeyx wrote:
Joshua Smith wrote:
limeyx wrote:
Joshua Smith wrote:
Sensors do wear out. Callibration is quick and easy. A decent check at 1ATA is to verify in ambient air (20.9%) and then use a known source of 100% 02.
Ahhhhh but how "known" is your known source ???? Maybe some shop-monkey slipped 21% Argon into the O2 supplies !!!
There are known unknowns and then there are unknown unknowns!
Damnit. Now I gotta buy an analyzer to verify my analyzer. Hmmmm- how can I verify my verification analyzer?
But then who verifies the verificator ? Tough issues !

Boy, it's like peeling an onion while herding cats, isn't it? Or maybe peeling a cat while herding onions.

Northwest Dive Club