Filmmaker Rob Stewart dies off Alligator Reef

[W W Meixner]

In all walks of life there are unknowing, curious, good people who seem to believe that "experts" (term used loosely) have come down from Mount Olympus and that we the unknowing should bow down and kiss their ring (please feel free to pick your ring of choice).

There are no gods...only those who have learned a skill well, who follow all the appropriate rules and regulations, who are honest and upright...and then there are those others...

Anyone who believes that a brand new certification card is a licence to use that card immediately to its outermost limits will surely become a statistic...case in point.

 

[doctormike]

The pressure from the breathing loop at the surface would push the air/gas out anyway, even if you had a chin strap. If you went unconscious you wouldn't be able to keep the seal around the mouthpiece to keep the gas inside the loop when your jaw relaxed.

There is evidence that this is incorrect: http://militarymedicine.amsus.org/doi/pdf/10.7205/MILMED-D-10-00420

I have gone back and forth about this myself. I don't use a chinstrap yet because I don't use a BOV, and I think that they should be used together. But I am strongly considering one...

This study of 54 rebreather divers losing consciousness underwater and 51 of them surviving (94%) is a VERY impressive statistic.

 

[RainPilot]

I only dive my RB with the KM48 full face mask. Almost all of the fatalities on RB could be avoided by retaining the DSV for a LOC event. If I pass out on the surface I won't flood the loop and may even be able to be rescued if I sink.

 

[TotDoc]

There is evidence that this is incorrect: http://militarymedicine.amsus.org/doi/pdf/10.7205/MILMED-D-10-00420

I have gone back and forth about this myself. I don't use a chinstrap yet because I don't use a BOV, and I think that they should be used together. But I am strongly considering one...

This study of 54 rebreather divers losing consciousness underwater and 51 of them surviving (94%) is a VERY impressive statistic.

It's important to note that this study was about loss of consciousness UNDER water. Also, this involved a buddy being available to intervene by placing them on a breathable mix.

At the surface is different, because while upright at the surface, some units generate a significant amount of positive pressure and will still push air out, even if the mouthpiece stays in place. This would make the unit quickly become negative, and you'd still go down... Unless someone was there to provide assistance.

Although a gag strap may well save lives, it's hard to show that this is the type of incident that could have been avoided if one were used. And again, since I believe he was on a revo, he may have been using a strap in this fatality.

 

[St John the Diver]

I have gone back and forth about this myself. I don't use a chinstrap yet because I don't use a BOV, and I think that they should be used together. But I am strongly considering one...
.

No reason to not use one. The bailout with a gag strap is to pull the mouthpiece down under your chin. Easy and the loop is well controlled that way. Better in fact than letting it float over your head.

 

[doctormike]

No reason to not use one. The bailout with a gag strap is to pull the mouthpiece down under your chin. Easy and the loop is well controlled that way. Better in fact than letting it float over your head.

Yeah, I might go that way, gonna try a few more hours using the configuration that I was trained with first. Still thinking about it, have heard reasonable arguments from experienced people both ways. I know that many consider BOVs to absolutely necessary, but I have been on two dives with CCR buddies who lost a mouthpiece, and I really like having a good old second stage under my chin, completely redundant.

 

[doctormike]

It's important to note that this study was about loss of consciousness UNDER water.

That's actually not true either. The article mentions that some cases involved LOC at the surface, both in the context of hyperoxic seizures and hypoxia.

 

[LandonL]

I would also agree with others here about the differences with LOC underwater (likely in a horizontal position) versus at the surface (more than likely vertical).

Thinking on the subject, the counter-lungs would have a large effect on the amount of pressure exerted at the surface. Looking at both models of CCR I dive consistently, I would think BMCLs would be better in this case than OTSCLs.

 

[St John the Diver]

Yeah, I might go that way, gonna try a few more hours using the configuration that I was trained with first. Still thinking about it, have heard reasonable arguments from experienced people both ways. I know that many consider BOVs to absolutely necessary, but I have been on two dives with CCR buddies who lost a mouthpiece, and I really like having a good old second stage under my chin, completely redundant.

It's a bit of a thread drift... But: I support the "BOV for Me, a long hose for Thee" system where I'm plumbed into my bailout bottle with a second medium length hose second stage to a regulator bungeed on that bottle like a stage bottle rig. That way you have something to hand off to Joe-Numpty quickly (try that with your necklaced second stage) and have 2X ways of bailing yourself. With a caustic cocktail you'll want to spit out what's in your mouth and grab the long hose. For any other bailout you use the BOV.

Your necklace system works, but if you use it ALSO put a hosed second stage on your bailout bottle to hand off.

 

[St John the Diver]

I would also agree with others here about the differences with LOC underwater (likely in a horizontal position) versus at the surface (more than likely vertical).

Thinking on the subject, the counter-lungs would have a large effect on the amount of pressure exerted at the surface. Looking at both models of CCR I dive consistently, I would think BMCLs would be better in this case than OTSCLs.

Makes no difference actually. Based on trying it. The key is a properly set OPV. OTS lungs actually tend to hold you face up far better when fully inflated.