Another lesson learned today

Jeremy · Post by **Jeremy** » Sun Mar 25, 2012 8:51 pm

I've been diving with a buddy of mine for over a year now. We've probably dove over 75 times together. As some of you know, I recently went throught the GUE Fundies course (AMAZING course btw), but my buddy did not. I've been diving Nitrox ever since Fundies.

So today at Mukilteo, there are like 4 classes. A ton of people. And there are cool things to see at depth at Mukilteo. So I suggest to my buddy that we go to the Troll. That involves a little trek to 125, pretty deep. I know through Fundies that doing such a dive on Nitrox is a bad idea. I suggest to my buddy (Nitrox certified, but hasn't actually dove it yet) that he and I switch a tank. I'll give him a Nitrox tank for the second dive (shallower) and he'll give me an air tank for the first dive (deeper). He says fine, and asks me for my analyzer. I say wait because it needs to be connected to your BC hose first. He says ok.

So we head down to the water. Classes everywhere. Zero viz. I'm like "lets beat these classes and just get down there!" So we descend without doing our predive (which for me is GUE EDGE). After one minute I feel a tug on my leg....turn around..see the thumbs up sign. So we ascend. Buddy's drysuit hose wasn't attached. He has problems attaching it. So I attach it for him. The entire time I'm thinking "this is very very bad Karma for not doing the damn GUE EDGE".

We continue. Hit the geodome. Keep going. Lot's of current. See the log. Whoops...too far. Change dive to satellite dish, man, and boat. Hit 126ft. Ascend. Hit dome again, see wolfie and octo, keep ascending. "Great dive!" we say at the surface. Head back to car. I switch out tanks and take buddy's tank back to him. "Thanks for the air bro!" I tell buddy. "Thanks for the Nitrox!" buddy tells me.

"What? .....you weren't diving Nitrox on that dive were you?"

"Yes"

Oh f*&$, I tell myself. We proceed to have a discussion on oxygen toxicity. Buddy realizes situation and gets down on himself. I get down on myself. Not good. If I did GUE EDGE, I would have caught the Dry Suit hose, and I would have caught the Nitrox. I would have told buddy "I'm diving Air at 3500 PSI", he would have said "I'm diving Nitrox 32%" and I would have said..."Um, we're heading back to the car my friend!"

Moral of story...It's TOTALLY worth it to do those pesky 4 minute predive checks. We are human, we WILL screw up, guaranteed. I will always predive check from now on, we got lucky today. I have dove with many many divers who skip this, and I did too for a long time. But lesson learned. Hope someone else can also benefit from this story.

ktb · Post by **ktb** » Sun Mar 25, 2012 9:36 pm

Glad everything turned out ok for you today!!

And I totally understand. I got into the bad habit of not doing pre-dive checks when I was always diving with the same people because "hey, we know each other." I started going to the Wednesday night dives in part because diving with new people FORCES me to stop and do a pre-dive check. It never hurts to go through the SADDDD list - Sequence (as in who is the captain?), Air, Depth, Duration, Direction, and Distance. (I think Deco could be considered a D as well, but since I never plan to go into deco with a new-to-me buddy, that's not an issue.)

H20doctor · Post by **H20doctor** » Sun Mar 25, 2012 9:44 pm

whats the Mod on 32 %... ? Yes i asked ..

Joshua Smith · Post by **Joshua Smith** » Sun Mar 25, 2012 9:49 pm

H20doctor wrote:whats the Mod on 32 %... ? Yes i asked ..

32% gives a pp02 of 1.6 @132 fsw.

Dusty2 · Post by **Dusty2** » Sun Mar 25, 2012 9:56 pm

Ouch! Coulda been a bad day! glad there were no ill effects.

LCF · Post by **LCF** » Sun Mar 25, 2012 10:12 pm

The biggest danger a diver can encounter (and we all will, and do) is complacency. I've posted about dives where I've skipped steps or rushed, and like you guys, I've been lucky enough that I didn't get hurt but I did get a good scare.

Among the many messages from the training I've taken, that I desperately want to share, is how easy it is to go through a dive plan and a gear check before diving. It takes very little time, puts the divers on the same page, and prevents a great many problems. And it's the first thing that gets tossed over our shoulders when we are in a hurry.

Thank you for yet another reminder of why one should stick to one's protocols.

eliseaboo · Post by **eliseaboo** » Sun Mar 25, 2012 10:25 pm

Gotta admit, I skip pre-dive checks way too often too. The "important" stuff is usually covered before we even get in the water, such as tank size, dive plan, etc (which is yes, not the proper way to do it, and yes, I should remember to do all this again in the water, and yes, it's *all* important...I can hear you all scolding me already)

Glad it all turned out ok. Good reminder for everyone.

cardiver · Post by **cardiver** » Sun Mar 25, 2012 10:31 pm

Was there a reason that you couldn't attach your buddies dry suit hose at depth?

Jeremy · Post by **Jeremy** » Sun Mar 25, 2012 10:33 pm

cardiver wrote:Was there a reason that you couldn't attach your buddies dry suit hose at depth?

He had noticed the problem when we were at about 8 feet, so there was no reason not to ascend and attach the hose.

H20doctor · Post by **H20doctor** » Sun Mar 25, 2012 10:48 pm

Joshua Smith wrote:
H20doctor wrote:whats the Mod on 32 %... ? Yes i asked ..
32% gives a pp02 of 1.6 @132 fsw.

So they could have hit 132feet.. And not had a prob..

Jeremy · Post by **Jeremy** » Sun Mar 25, 2012 10:54 pm

H20doctor wrote:
Joshua Smith wrote:
H20doctor wrote:whats the Mod on 32 %... ? Yes i asked ..
32% gives a pp02 of 1.6 @132 fsw.
So they could have hit 132feet.. And not had a prob..

Max working pp02 is 1.4, max resting pp02 is 1.6.

If there was an issue at depth and my buddy was on Nitrox, we both run the risk of O2 toxing. He, due to the work. And me, due to relying on his gas supply in case I have an issue with mine.

CaptnJack · Post by **CaptnJack** » Sun Mar 25, 2012 11:00 pm

Every local shop I've been to expects you to analyze the gas and mark it there. Was their no analysis tape on the crown of nitrox tank?

Joshua Smith · Post by **Joshua Smith** » Sun Mar 25, 2012 11:01 pm

Jeremy wrote:
H20doctor wrote:
Joshua Smith wrote:
H20doctor wrote:whats the Mod on 32 %... ? Yes i asked ..
32% gives a pp02 of 1.6 @132 fsw.
So they could have hit 132feet.. And not had a prob..
Max working pp02 is 1.4, max resting pp02 is 1.6.

If there was an issue at depth and my buddy was on Nitrox, we both run the risk of O2 toxing. He, due to the work. And me, due to relying on his gas supply in case I have an issue with mine.

Possible. Not very likely, but possible. Personally, I wouldn't worry very much about that kind of 02 exposure. Bigger issue is simply not being aware of what gas you're breathing, the way I see it. Glad you're both ok.

Jeremy · Post by **Jeremy** » Sun Mar 25, 2012 11:02 pm

CaptnJack wrote:Every local shop I've been to expects you to analyze the gas and mark it there. Was their no analysis tape on the crown of nitrox tank?

Yes, my Nitrox tank had the typical blue tape with 32% written on it.

Jeremy · Post by **Jeremy** » Sun Mar 25, 2012 11:05 pm

Joshua Smith wrote:
Jeremy wrote:
H20doctor wrote:
Joshua Smith wrote:
H20doctor wrote:whats the Mod on 32 %... ? Yes i asked ..
32% gives a pp02 of 1.6 @132 fsw.
So they could have hit 132feet.. And not had a prob..
Max working pp02 is 1.4, max resting pp02 is 1.6.

If there was an issue at depth and my buddy was on Nitrox, we both run the risk of O2 toxing. He, due to the work. And me, due to relying on his gas supply in case I have an issue with mine.
Possible. Not very likely, but possible. Personally, I wouldn't worry very much about that kind of 02 exposure. Bigger issue is simply not being aware of what gas you're breathing, the way I see it. Glad you're both ok.

Sounds like you are probably right. I was thinking the O2 tox hit was pretty risky at 125ft with Nitrox, but maybe it isn't.

eliseaboo · Post by **eliseaboo** » Sun Mar 25, 2012 11:19 pm

Jeremy wrote:
CaptnJack wrote:Every local shop I've been to expects you to analyze the gas and mark it there. Was their no analysis tape on the crown of nitrox tank?
Yes, my Nitrox tank had the typical blue tape with 32% written on it.

I read it as his buddy misunderstood what he meant when he said "swap tanks". Jeremy meant to both dive air first and nitrox second, and his buddy thought he meant to swap which buddy was diving nitrox on dive 1.

Jeremy · Post by **Jeremy** » Sun Mar 25, 2012 11:25 pm

eliseaboo wrote:
Jeremy wrote:
CaptnJack wrote:Every local shop I've been to expects you to analyze the gas and mark it there. Was their no analysis tape on the crown of nitrox tank?
Yes, my Nitrox tank had the typical blue tape with 32% written on it.
I read it as his buddy misunderstood what he meant when he said "swap tanks". Jeremy meant to both dive air first and nitrox second, and his buddy thought he meant to swap which buddy was diving nitrox on dive 1.

Exactly

kdupreez · Post by **kdupreez** » Mon Mar 26, 2012 12:55 am

Yeowza! Like I said in fundies.. there's a reason for everything.. even those pesky 4 minute pre-dive checks

MOD for 32% is 111ft @ 1.4 PPO2 (But we actually cap the dive at 100ft because of Narcotic Depths.. and thats equivalent to 1.2 PPO2)

Thanks for sharing!! I'm really glad everything turned out OK and also really glad that it was a good learning oppertunity.. You were edging towards of 1.6 PO2 (if you analyzed it properly and your analyzer wasnt a little off) and thats the danger zone for even resting/deco dives.. I know a lot of people that will probably go: "bwha, you'll be fine, I dive 1.6 a lot and I'm still fine...."

Well, you'll probably not have any issues with such short exposure times and PO2 levels., but the problem here is: "probably".. And that "probably" is leaning left towards the side of more probable that something will go wrong than less probable and when dealing with a central nervous system seizure that could lead to drowning and death, I would much rather err towards the very least probable side..

The problem with O2 toxicity is that "we just dont know".. as in we dont know why it happens and why some people get hit much sooner than others (if at all) and why the same person gets hit at random PO2 levels and random exposure times on different days.. Back in WW2, Prof. Kenneth Donald spend well over 3 years of dedicated research on this subject and after thousands of human trails, the research was deemed "inconclusive".. i.e. unpredictable and root cause unknown.

The only results from these empirical studies were that with low exposures of 1.4 and lower, its least likely to occur..

Call me crazy, but I say rather err on the side of caution.. I'd much rather come back and do the dive again with the right gas, than play Russian roulette and end up unlucky..

Dusty2 · Post by **Dusty2** » Mon Mar 26, 2012 1:24 am

I have to agree on the safe side. To much of this is based on the law of averages and everyone is different. Even the same person will be different depending on so many factors. I know several guys who dive nitrox and set a 1.5 or even 1.6 on their computers and say they never had a problem. To me that's kinda like the guy who has a half a dozen beers and drives home because he has never had a problem doing it. Sure, He's done it many times without problems. Does that mean he is not endangering himself and allot of other people? Hell no!

When it comes to messing with my body chemistry I'm looking for the safest possible route. Going into convulsions at 125fsw is not survivable and there are no warning signs. My simple rule is never go for the max when it's your it's life your talking about.

CaptnJack · Post by **CaptnJack** » Mon Mar 26, 2012 8:20 am

Jeremy wrote: Sounds like you are probably right. I was thinking the O2 tox hit was pretty risky at 125ft with Nitrox, but maybe it isn't.

In the "old days" ppO2 1.6 was the norm. I don't think there was a enormous risk of actual toxicity in the 5-10mins you were ppO2 >1.4

I'd be more concerned that you followed each other right to the edge of recreational limits and nobody stopped and said "whoa". About the gas choice or just what the dive plan was at all.

Rooinater · Post by **Rooinater** » Mon Mar 26, 2012 9:08 am

Yep, I remember when I took my nitrox class the 120' range on nitrox was the norm, 132' was the MOD we put on the tanks. I don't do it as often anymore, but occasionally I am guilty of a ppo2 1.5 since I started diving nitrox again. I was actually caught off guard when I started diving again and the charts had a MOD of 111'. But after a few discussions with more newly certified nitrox divers and instructors, I get the reasoning. If and when I dive that kind of profile its usually the gas I have and the plan is discussed predive, and max depth is set by whoever wants the lowest ppo2.

lamont · Post by **lamont** » Mon Mar 26, 2012 9:40 am

yeah, i'd be more actually concerned about the narcosis, viscosity of the gases you were breathing, work of breathing, CO2 buildup, etc. the plan to go to 125 on nitrox raised my eyebrows more than the ppO2.

taking the hot mix to 125 is more indicative of a bit of lack of planning rather than running a huge actual risk (of course, if you make a practice of it, then absolutely, the 1.6 ppO2 limit is there for dives at rest on deco not working hard, and there still is a tox risk there, which on a long enough timeline you will eventually find, particularly for the working part of coldwater dives -- so you should be keeping your ppO2 to 1.2 planned / 1.4 max for rec diving -- but on this one dive it was very unlikely to bite you...).

Joshua Smith · Post by **Joshua Smith** » Mon Mar 26, 2012 9:40 am

CaptnJack wrote:
Jeremy wrote: Sounds like you are probably right. I was thinking the O2 tox hit was pretty risky at 125ft with Nitrox, but maybe it isn't.
In the "old days" ppO2 1.6 was the norm. I don't think there was a enormous risk of actual toxicity in the 5-10mins you were ppO2 >1.4

I'd be more concerned that you followed each other right to the edge of recreational limits and nobody stopped and said "whoa". About the gas choice or just what the dive plan was at all.

Yep. Of course, Koos is right, and people HAVE toxed at 1.6 before, but that's usually with prolonged exposure. Individual tollerance for elevated pp02 exposure is extremely variable. So, to play it safe, stick to the rules.

Jeremy · Post by **Jeremy** » Mon Mar 26, 2012 9:47 am

lamont wrote:the plan to go to 125 on nitrox raised my eyebrows more than the ppO2.

Just to be clear, the "plan" was to go to 125 on air. The second dive to 60ft was going to be done on Nitrox. My buddy confused the gases which I would have caught if I had done a predive.

The goals and gases for the dive were all discussed prior to the dive. Obviously there was a misunderstanding.

I agree that even on air narcosis is a legitimate concern.

Jeremy · Post by **Jeremy** » Mon Mar 26, 2012 9:53 am

kdupreez wrote: Call me crazy, but I say rather err on the side of caution.. I'd much rather come back and do the dive again with the right gas, than play Russian roulette and end up unlucky..

A 100ft maximum depth on non-helium mixes just seems very conservative and makes a visit to the boat a very expensive dive to do properly.

But I agree, the conservatism makes sense and there is no reason to take a crazy risk just to go look at an unimpressive boat.

I guess I'm having a hard time getting out from the "lot's of other divers go to the boat on air, why can't I?" thinking. I think I'll stick to the 100ft max going forward.

Northwest Dive Club