OOA buddy...

[Geek]

We were shallow enough and didn't have any deco so we just went to the surface. To many things were going wrong (OOA, back up reg, etc) to stay under at that depth and fiddle with anything.. now if it was 150' and we had 20 min of deco still.. we probably would have figured it out on the bottom.

I think you mean on the ascent...
Unless you are bringing mad volumes of bailout.

LOL, funny thing was I thought about this. I did open the center valve.... Only because I was the one that picked up the tanks and analyzed it and your right, I only analyzed one (I'll keep this in mind) BUT as I thought about it I analyzed the tank he hadn't been breathing on so I knew what was in that one

Ummm your doubles wearing buddy didn't analyze his own doubles either?

I don't know that it requires "Mad" Volumes of bailout to take a minute and think about the problem at 150' Of course at 150' are you going to be slinging a bailout bottom mix? Probably not since you are wearing doubles and slinging deco. The "bailout" bottom mix is your buddy's long hose and there should be plenty for both of you to take a minute and think about a problem before heading up to your MOD of your first deco gas. On the Meg I sling bottom mix for the depth that I'm diving which will be enough to get me out with deco and a "minute or so" of WTF happened, which should be MORE than plenty for my buddy that is on OC to get to his first gas switch... if I was doing those kinds of dives on the Meg yet, which I'm not


No, he had to work past when the shop would have been open and I had to get my cylinders as well, it was a dive at Les Davis, and the Tanks where filled with air, only reason I did analyze the doubles was because I'm anal about analyzing every cylinder since I started diving the Meg, normaly he wouldn't have analyzed them at all since it was only air, Ya, I know, I know, should always analyze but realisticly how many people analyze their tanks when they get plain air?

[lamont]

i had a rental tank once which didn't have the isolator open -- it had been left closed by someone who was in a class and had left it closed after getting out of the water. the guy filling the tanks had only filled one side and left the isolator closed as well. caught it during gear up after i'd hooked regs and such up to the tanks and cracked all the valves open. since the other tank was drained nearly 100% it settled down at around 1600 psi, which wasn't enough for the cave dive that we wanted to do.

and while this suggests checking tanks actually at the fill station before driving off with them first, i did manage to catch this problem at the next available opportunity when i still wasn't even in my drysuit yet. i also typically check on the surface after gearing up that valves are open (particularly so i don't jump in with any valves closed) and i check in the water as part of gear check, then typically do a mod-valve after hitting the main line. every time i check my valves i make it a habit to check all three of them.

and i hardly ever have just plain old 21%, but tanks always get analyzed. i will admit that i don't normally analyze both sides...

[CaptnJack]

If you can figure out which side is empty, which side was analyzed, how much gas is actually remaining, open the isolator, and then convince your OOA buddy in doubles who didn't analyze either side that he'll be "just fine" going back to his own reg after going OOA all in a minute at 150' I'd be impressed.

Personally I'm going up where the open circuit gas that does remain, whichever tanks it might be in, lasts alot longer. We can discuss WTF is going on and what is safe to breathe (and what might be iffy) a few ATA shallower.

[Joshua Smith]

If you can figure out which side is empty, which side was analyzed, how much gas is actually remaining, open the isolator, and then convince your OOA buddy in doubles who didn't analyze either side that he'll be "just fine" going back to his own reg after going OOA all in a minute at 150' I'd be impressed.

Personally I'm going up where the open circuit gas that does remain, whichever tanks it might be in, lasts alot longer. We can discuss WTF is going on and what is safe to breathe (and what might be iffy) a few ATA shallower.

Seems easier just to dive a rebreather, where you usually only have a vague idea what gas you're breathing at any given moment.

[Geek]

Seems easier just to dive a rebreather, where you usually only have a vague-ish idea what gas you're breathing at any given moment.

Fixed that for ya Josh

[browntown]

Do NOT open the isolator underwater unless you have analyzed both tanks (which most people rarely do) and positively know with analysis tape what is in the other tank.

So I'm still learning about tech and probably showing my ignorance but this confuses me. Under what circumstance would one side have a different mix than the other? When diving doubles both sides comingle when the isolator is open right? If a valve goes bad you can isolate the non leaky side and use that post but shouldn't worry about it being different. I thought the redundancy of the system was the point. If they aren't the same then it can't be a redundant system. So if you know that the isolator was open when filled (mentioned by OP) and accidentally closed after filling, then the tanks have to be the same gas don't they? Or does the density of the different gasses make uneven comingling?

Again, I'm still in my learning stage and not diving doubles yet so forgive my lack of understanding.

[Joshua Smith]

Do NOT open the isolator underwater unless you have analyzed both tanks (which most people rarely do) and positively know with analysis tape what is in the other tank.

So I'm still learning about tech and probably showing my ignorance but this confuses me. Under what circumstance would one side have a different mix than the other? When diving doubles both sides comingle when the isolator is open right? If a valve goes bad you can isolate the non leaky side and use that post but shouldn't worry about it being different. I thought the redundancy of the system was the point. If they aren't the same then it can't be a redundant system. So if you know that the isolator was open when filled (mentioned by OP) and accidentally closed after filling, then the tanks have to be the same gas don't they? Or does the density of the different gasses make uneven comingling?

Again, I'm still in my learning stage and not diving doubles yet so forgive my lack of understanding.

Good question. Basically, its all about knowing, 100%, beyond a shadow of a doubt, exactly what you're breathing at any given time. If someone has gone so far down the road of missed checks that one finds the isolator closed underwater, they can't be really, really sure that the left side and right side have identical contents any more. Yes, if the isolator was open when they were filled and analyzed, then the contents should be identical. But if there's any doubt about that, you're probably better off not opening it.

That said.....if they were MY personal dubs, and I was intimately familiar with what had been in them over the last few fills, I'd probably have a pretty good idea that I wasn't about to mix a tank of 36% nitrox into another half full tank of trimix, for example- which could have disastrous results, depending on the dive profile.

[CaptnJack]

Seems easier just to dive a rebreather, where you usually only have a vague idea what gas you're breathing at any given moment.

LOL touche

[Geek]

What Josh said, in this case we knew there has never been anything other than air or 32% in these tanks, since they were dropped off and picked up within 3 hours the chances of one side being filled with a Hypoxic mix was closer to zero than I care to calculate... a Hyperoxic mix would have been more likely and at 50' at the end of a dive on the way in etc still wouldn't have been life threatening... however at 150' a Hyperoxic mix like 100% would have you toxicing in no time flat.

[lamont]

Do NOT open the isolator underwater unless you have analyzed both tanks (which most people rarely do) and positively know with analysis tape what is in the other tank.

So I'm still learning about tech and probably showing my ignorance but this confuses me. Under what circumstance would one side have a different mix than the other? When diving doubles both sides comingle when the isolator is open right? If a valve goes bad you can isolate the non leaky side and use that post but shouldn't worry about it being different. I thought the redundancy of the system was the point. If they aren't the same then it can't be a redundant system. So if you know that the isolator was open when filled (mentioned by OP) and accidentally closed after filling, then the tanks have to be the same gas don't they? Or does the density of the different gasses make uneven comingling?

Again, I'm still in my learning stage and not diving doubles yet so forgive my lack of understanding.

There was an accident in florida (Eagles Nest?) years back when someone got a fill where the isolator had been closed and most of the O2 went in on one side and most of the helium went in on the other. The result was hypoxia and I think she(?) wound up brain dead?

Probably 6-8 years ago, so I may be misremembering the details... not enough caffeine today yet to bother googling it...

[spatman]

There was an accident in florida (Eagles Nest?) years back when someone got a fill where the isolator had been closed and most of the O2 went in on one side and most of the helium went in on the other. The result was hypoxia and I think she(?) wound up brain dead?

Probably 6-8 years ago, so I may be misremembering the details... not enough caffeine today yet to bother googling it...

http://www.sptimes.com/2005/09/29/Tampa ... 130_.shtml

[Joshua Smith]

There was an accident in florida (Eagles Nest?) years back when someone got a fill where the isolator had been closed and most of the O2 went in on one side and most of the helium went in on the other. The result was hypoxia and I think she(?) wound up brain dead?

Probably 6-8 years ago, so I may be misremembering the details... not enough caffeine today yet to bother googling it...

http://www.sptimes.com/2005/09/29/Tampa ... 130_.shtml

Good god. That's horrific. I can only guess that they were partial pressure blending through different posts with the isolator closed.