Diver one of sixteen to die using high-tech gear

[rcojr]

[quote='DRE link' dateline='1046401189']
[quote] I can\"t speak to the Cislunar I never considered it as it was way out of my means(about $25,000)
Checking the sensors(there are three) at depth is easy. Being a good Tec. diver you always know what fraction of 02 you are breathing and you know how deep you are. It's a simple matter to take f02xata and calculate the PP02. When you know that you just do a Diluent flush and check to see if your 02 sensors are reading correctly. John J. that just posted to the list puts duct tape on the back of his handset and enters all the numbers on the surface(no math a depth)
[/quote]


I'm sorry if I'm misunderstanding this, but if you have a machime that gives you your bottom gas by mixing O2 and a diluent on the fly, your fraction of O2 is determined by this mixing process. So aren't you basing your fO2 on the a priori assumption that that is what the machine is going to give you anyway. So in case the O2 sensors are all off the mark, the machine will mix you a gas which the machine assumes gives you the correct ppO2 at depth and that's the readout you'll get on your display (based upon the data from those same O2 sensors). Now you have to assume that's something might be wrong, do the diluent flush and then find out that your sensors are off the mark, all while you're 260ft inside the Kamloops. Then you have to deploy your bailout bottle (unless you have left the bottles outside of the wreck to maintain a smaller profile) because you can no longer be sure of what your machine is mixing for you - that is, if you haven't toxed out yet at that point and make it to the surface and do your entire deco on your bailout bottles. At the same time your team member has a catastrophic gas failure on his Inspiration, his deco bottle starts freeflowing and then what?
Granted, this might be somewhat of an unusual scenario, but weirder things have happened...

Also, could you please elaborate on how you calculate your gas requirements for any given dive?
[/quote

My mistake instead of saying the fraction of 02 you are breathing I ment to say the fraction of 02 in the diluent bottle . When you mix your gas for the diluent bottle it has to be a breathable mix for the depth that you are going to
(ie Kamloops at 260 10/60)
As far as your scenario I feel if I answered it you would just come back with one three time as wierd and that isn't a game I'm here to play.
[/quote]

[DRE]

"My mistake instead of saying the fraction of 02 you are breathing I ment to say the fraction of 02 in the diluent bottle . When you mix your gas for the diluent bottle it has to be a breathable mix for the depth that you are going to
(ie Kamloops at 260 10/60)"

OK, so your bottom gas at max depth is fine, but isn't one of the perceived or advertised benefits of a CCR that it maintains a constant ppO2 for the inspired gas by adding O2 into the mix? So again, how do you know for sure that your sensors are telling you the truth regarding the inspired fO2 as you're shallower than max depth where I assume your solely drawing from the diluent bottle.

"As far as your scenario I feel if I answered it you would just come back with one three time as wierd and that isn't a game I'm here to play."


Could you give me straight answer on how you calculate your gas requirements (both primary and bailout scenarios) for a given dive, let's say Kamloops (max depth 260, 20 minute BT)? I don't think that's a far-fetched question as we're talking about a routine tech dive.
And BTW, I don't think that the above scenario was weird in any way - I just try to think through any possible scenario and what I need to do in terms of planning, equipment, etc to make sure I can make it back from that dive. I honestly believe that if you aren't this thorough about your diving you have no business being in the water in the first place.

[DRE]

"When the O2 sensor(s) fail and the unit starts mixing the wrong gases, won't the computer readout tell the diver what ppO2 is being mixed? Even if it gives the wrong number shouldn't the diver know if the number is correct or not? I have to believe that the CCR diver isn't on autopilot. He should know these numbers at each given depth."

Correct, you'd assume that the diver is not on autopilot, but some of the cases in which divers died using their unit was that they were not aware of the audible signals the machine gave them of either a hyperoxic or hypoxic mix. So I believe there is a problem with the warning mechanisms of the unit if people fail to hear them.
Secondly, what's the fun of diving when you constantly have to watch your two computer readouts and check 'em against one another - you might as well stay home and watch the weather channel. Furthermore, the placement of the displays in the frontal area of the diver, and also the placement of the counterlungs on the front side, increase the diver's vertical profile, which isn't any smaller than a hogarthian backmount config, but with a lot more stuff in the way of easily clipping off stage bottles, primary and backup lights, reels, liftbags, etc.
Third, the sensors are placed downstream from where gas is added to the loop. This means that if a high dose of O2 is added to the loop, the diver will notice it on his display as he is about the inspire that mix - it only takes 2 to 3 breaths at depth with an excessive ppO2 to tox. That's why the much more expensive units (such as the Cis-Lunar have the sensors placed upstream so that the machine itself can fix the problem before it actually occurs). The reason why the Inspiration has the sensors downstream is because the design was inspired by Navy pure O2 rebreathers, where it didn't matter that the sensors are downstream since pure O2 is constantly being pumped into the loop, adn toxing out isn't an issue because of the much shallower deths these units are used at (the Navy used to allow pure O2 rebreather use upto 60ft, I'm not sure if they still do. Keep in mind however, that Navy combat divers are in extreem physical condition, and they are screened for oxtox susceptibility - none of which is applicable to the average tech diver).

[JNitrox]

There are a few things that we need to remember here.
1. CCRs have been used in many settings (military, commercial diving, and more recently recreationally) for decades in "mixed gas" configurations (not just pure O2).
2. Having or not having a buddy does not guarentee safety or failure in diving. Accidents can still happen no matter what training, equipment, or gear configuration you have. That is why we call them accidents.
3. Diving is supposed to be fun. We need to spend more time nurturing the sharing of information rather than forcing our favorite equipment or diving style on others.
4. If you take the time to research (and I mean really research) a topic and then form an opinion it makes you a better diver. Don't just look to one source or one "Expert" for information.
Safe diving

[DRE]

"2. Having or not having a buddy does not guarentee safety or failure in diving. Accidents can still happen no matter what training, equipment, or gear configuration you have. That is why we call them accidents."

I'm sorry but if you do things correctly and have thought through a multitude of different scenarios, accidents are merely an correctable nuisance during a dive. I don't accept death as a reality in my diving - there's nothing worth dying for UW. This is a view, however, that isn't shared by the vast majority of the tech diving community, who'd rather thrive on their testosterone than to take a close and critical look at their own diving practices.


"3. Diving is supposed to be fun. We need to spend more time nurturing the sharing of information rather than forcing our favorite equipment or diving style on others."

I totally agree.


"4. If you take the time to research (and I mean really research) a topic and then form an opinion it makes you a better diver. Don't just look to one source or one "Expert" for information."

I couldn't have put it any better.

[jasondbaker]

I think what jnitrox is saying is that no dive system or practice is perfect. Accidents can and do happen. One sysytem of diving may be 99.999% reliable, and the other 99.997%. But nothing is absolute. I don't think this viewpoint means that accidents are acceptable, just that they are possible.

DRE, are you arguing the merits of CCRs in general or just the buddy inspiration?

[DRE]

CCR's in general. Maybe with the exception of the Cis-lunar there is no CCR on the market that would withstand the rigors I place on my technical diving in terms of safety. All have what I consider major design flaws, which would manifest itself at the least conventient moments during a dive. Even the Cis-lunars, which can work for 24 hours continuously, didn't get the work done in Wakulla. In fact, the Wakulla II project, which used these rebreathers, didn't get as far as the setup dives currently conducted by Wakulla III on OC. And by the way, Wakulla III has a 100% safety record, which is the only safety record acceptable to me.

[jasondbaker]

DRE, did the WKPP do a report on their experience with the CCRs for their project? I would like to read this.

Do you drive to work/school every day in a car? Wouldn't you be much safer if you drove a tank? I'm playing a little devils advocate here.

[FMT]

Just to clarify, Wakulla II project and Wakulla III project were done by two different organizations. WII was done by the US Deep Caving Team who believed in the use of CCRs and used the Cis-Lunar. WIII was done by WKPP who do not believe in the use of CCRs and they used and use the SCR RB-80.
T

[FMT]

For WII check out
For WIII check out

At usdct.org there is a brief description of the features of the Cis-lunar.

T