Why CCR?

[wedivebc]

I don't mean to harp on this point, I am just trying to understand. You're saying that most CCR deaths are due to pilot error... But error in setting up the unit, or error in pushing the limits.

That's entirely different than the common (?) perception by OW OC divers that a perfectly functioning CCR may suddenly stick a knife in your back.

No please, harp away
There have been an inordinate amount of RB fatalities that were caused either directly or indirectly by diver error. I am not talking about something going wrong with the unit then the diver not responding correctly I am talking about bad decisions made by divers prior to the dive that ultimately caused their demise.
I may be stupid gas choices, improper maintenance or pre-dive setup or diving beyond the limits of their training and experience. Most commonly it is a combination of the above.
I only know of one case where an unexpected RB malfunction directly caused a divers death.

 

[Kevin Carlisle]

No please, harp away
There have been an inordinate amount of RB fatalities that were caused either directly or indirectly by diver error. I am not talking about something going wrong with the unit then the diver not responding correctly I am talking about bad decisions made by divers prior to the dive that ultimately caused their demise.
I may be stupid gas choices, improper maintenance or pre-dive setup or diving beyond the limits of their training and experience. Most commonly it is a combination of the above.
I only know of one case where an unexpected RB malfunction directly caused a divers death.

Makes me wonder how many of those ever said " if something goes wrong I will just bail " and neglected maitenance or cut the pre dive inspection short.

 

[Matt S.]

Thank you for clarifying that.

 

[wedivebc]

Makes me wonder how many of those ever said " if something goes wrong I will just bail " and neglected maitenance or cut the pre dive inspection short.

One key point to remember and this is a huge shortcomings of the RB, too many times the diver is unaware that he is in trouble until it is too late to do anything about it. It is for that reason that I seldom dive solo on RB. I have already been saved by a buddy once. If not for him I certainly would not be here.

 

[HowardE]

One key point to remember and this is a huge shortcomings of the RB, too many times the diver is unaware that he is in trouble until it is too late to do anything about it. It is for that reason that I seldom dive solo on RB. I have already been saved by a buddy once. If not for him I certainly would not be here.

There have been a few instances where Solo Diving on RB's has been the demise of the diver. My instructor said, "always - always dive with a buddy when diving a rebreather"

 

[hobodiver]

Maybe. But I wasn't necessarily talking about the ones last week.

And... I'd bet you that in the very recent accidents. The rebreather wasn't at fault.

Given how rare it is to actually know what happened after the fact, I'm not sure that's a bet you would collect on.

 

[gcbryan]

I think many/most RB deaths would have been prevented if all RB users wore full face masks and didn't dive solo.

 

[wedivebc]

I think many/most RB deaths would have been prevented if all RB users wore full face masks and didn't dive solo.

Quite a number of RB fatalities are the result of CO2 issues. A FFM adds a greater level of complication for bailout if you are switching to an OC regulator. A diver facing high CO2 levels may not have the mental capacity or motor skills to execute that switch. Many think the solution to that is to add a BOV. Have you ever worn a FFM that was attached to a RB? It is very restrictive and bulky. Add a BOV and I am told you can barely move your head in any direction due to the bulk.
Although I believe solo diving on a RB is less safe than OC I should point out that in quite a number of incidents that I can think of the diver was with one or more buddies that were unable to render assistance mostly due to the fact that by the time they recognized an issue it was too late.
I am reminded of a near miss that happened near here a while ago. A diver on an Optima (likely not trained) had an issue that caused a huge CO2 bypass. The buddy saw the distressed diver, removed the loop, and swam him back to the boat where he was evacuated to the hospital. The only reason the buddy was there to render assistance was he had forgotten his weight belt on the boat and remained on the surface, the other in the group had already began their dive.

 

[brockbr]

I dont know about the hud but in a cave silt out, you see zero.. Be nice to hear from someone who has bee in that before..

CD have you ever tested yours in those conditions?

I have been in an absolute ZERO clay based siltout and can tell you form experience that my Shearwater HUD pressed against my mask clearly showed my pO2, and that's all I would need to control the unit.

The Shearwater HUD (and many others like it operate the same way) contains 3 LED's. Each LED represents the pO2 in the loop. Taking a single LED, each red flash indicates .1 below 1.0 pO2, and each green flash is .1 above 1.0 pO2. An orange flash indicates (red+green) a 1.0 pO2.

Using a 3 cell HUD also allows you to do diagnostics in low viz situations. For example - During the siltout become concerned that I have a cell going bad. A dil flush will tell me which cells are reading properly, and which cells are lying.

(For the uninitiated, a dil flush would be flushing the breathing loop with diluent. Since you know what gas you have in your dil, you can figure out what the pO2 should be given your depth Here's an example at Jackson Blue - 98ft = ~4ATA ... An Air dil should give you 4 * .21, or .84. You can verify this on the HUD - You should get 2 red flashes (1.0 pO2 - 2 red flashes = .8) So even in a full siltout, I can still monitor my pO2 with a high degree of confidence)

Well I have heard this before too. If you are gonna do CCR, you need to do it most of the time. Not some of the time. That makes sense to me.

Ahhh - But like I've always told you, a) there is a tool for each job and b) A catastrophic failure on CCR turns you into an OC diver - You better stay polished up on your OC skills.

Generally speaking, my **personal** view is that CCR divers should have most of the following traits:

0) Be a solid OC diver

1) Be AN/Deco at the VERY LEAST - PERIOD

2) Be mechanically inclined. Rebreathers require a descent mechanical ability.

3) Be dedicated to setup and tear down. Many accidents have happened to rebreather divers *on the setup bench*, meaning the CCR was put together with a flaw.

4) Realize that O2 monitoring is NOT perfect. Learn, understand, test and analyze your O2 sensors. UNDERSTAND how they work, and how they fail!

5) NEVER, EVER become complacent on a rebreather. (Because of this, I personally dive a mCCR)

For me, I dive OC when it makes sense, and CCR when it makes sense. My choice is based on the following benefits observed for CCR (in no particular order and not complete):
1) Silent, with a warm moist loop

2) Comfortable to dive

3) I am amid other CCR divers who can act as a team

4) Trimix is inexpensive for CCR

5) On a new scrubber on my CK, I get 6 hours EASILY.

6) Peace of mind in an overhead environment (goes for cave or deco)- I won't run out of gas any time soon.

7) ALWAYS an optimized mix for the depth. Never get blown of an alternate dive due to a bad mix.

The following are disadvantages for me that usually cause me to pick OC for a given dive:
1) Slightly more gear intensive resulting in a more complex setup

2) Dive is shallow/NDL/short - Generally not worth the setup and tear down time.

3) Gear complexity (different from intensive) - My toolbox of spares is well stocked, but there is more to break. A remote dive can be ended/canceled due to broken equipment (although I might add that in many hundreds of hours on my CK, I've never missed a dive due to a broken part)

4) Mixed team. If I am diving with an OC team for a non-trimix dive, and I am the only CCR diver, I'll generally dive OC.

These are just some random thoughts. Kevin knows me pretty well, and he also knows how often I dive CCR (which is to say a LOT).

In closing, I'll say this - I recently did some very deep diving in Cay Sal Bank - I **personally** would have NEVER even thought of doing the deepest dives on OC - I did them on CCR.

Just my $0.02

 

[Kevin Carlisle]

Thanks Brock.. Was hoping you would jump in. I forgot about your siltout in JB..