Mouthpiece retainer strap

[Vanny]

Yep what WFO said. Always know your Po2. The electronics , kit etc are just there to assist you in decision making not make the decision for you. It’s a slight shift of mind. So Paul H talked about one incident where 2 cells were current limited , cell 1 went sky high the diver suffered hyperoxia. The unit would’ve been using voting logic and injecting o2 based on the 2 cell readings that were limited , so pissing in o2 based on 2 cells that could never read that high.

So our manual defence to that is clearly having prepped the unit and checked it before entering the water , then in the water injecting a small amount of o2 into the loop to push the po2 above set point. Linear response across the cells then flush back down. No harm in doing this a few times through a dive , particularly as cell failure , I understand, can be more common when the scrubber stack is up to temperature, for the inspo that’s about 20 mins and humidity is increasing.

This was one of the examples where hyperoxia brought unconsciousness followed by drowning.

[WFO]

Yep what WFO said. Always know your Po2. The electronics , kit etc are just there to assist you in decision making not make the decision for you. It’s a slight shift of mind. So Paul H talked about one incident where 2 cells were current limited , cell 1 went sky high the diver suffered hyperoxia. The unit would’ve been using voting logic and injecting o2 based on the 2 cell readings that were limited , so pissing in o2 based on 2 cells that could never read that high.

I was specifically on about that one above, IIRC the guy was instructing on a course, it was about the time of the great cell shortage caused by the ginger ambulance chaser and his merry gimp so cells were failing all the time and the guy had silenced cell alarms repeatedly.

Makes sense when you remember Graham is likely to dive his JJ in the GUE configuration, which the questionable deployment of a long hose under the loop. Deploying the long hose with a retaining strap in place will introduce the risk of not looking fabulous, a clear rule 6 violation

He specifically said about removing the loop from ones gob!
Wouldn't the long hose be clipped off to a chest D ring and hence still accessible? (and even breathable even still clipped on probably)

[dwhitlow]

He specifically said about removing the loop from ones gob!
Wouldn't the long hose be clipped off to a chest D ring and hence still accessible? (and even breathable even still clipped on probably)

I believe the GUE JJ configuration requires the long hose to be stowed under the loop, much as a twinset diver will stow their long hose.

The long hose is carried under the loop when diving the rebreather. The chances of having to donate to another GUE rebreather diver is low, as both carry redundant bailout. Still, GUE maintains that the capacity to donate gas must be present. The process is more likely to involve a handover of the long hose rather than a donation.

Still, if needed, such a donation is made possible by either removing the loop temporarily or by simply donating the long hose from under the loop.

[graham_hk]

There are lots of reasons I can think of that I may wish to remove a loop from you mouth - like clearing dribble/lung batter from exhale hose or bailout. All of which are much more likely than loss of consciousness. I don't wear a crash helmet in day to day life although undoubtedly it would probably have some advantage if I passed out and fell over. I don't wear a crash helmet as I find it rather inconvenient given its limited benefit and the unlikeliness of needing it, like a gag strap. Your mileage may vary and I don't mind at all what anyone else dives

As has been stated much more important to know your po2 and have situational awareness.

As for the long hose - except during training (#rule6), its even more unlikely that I'd need to get that out in a hurry than going unconcious so I am not worried about gag strap for that reasons ... It had been discussed removing it but that would just cause the internet to melt down (both camps + and - GUE)

[Brad_Horn]

it was about the time of the great cell shortage

https://xray-mag.com/content/john-la...2%80%94dies-78
"On 2nd April 2010 Teledyne Analytical Instruments issued a press release stating that they would no longer supply oxygen sensors for the commercial and rebreather markets. This was allegedly because on 4 October 2008 a British diver apparently suffered from an oxygen problem on a rebreather dive in Egypt. Upon surfacing they questioned the quality control of the oxygen cells. Over time the situation escalated and lawyers became involved. Teledyne settled out of court, and then made the decision to pull out of the rebreather market.
The action of Teledyne pulling out of providing oxygen cells to recreational and technical rebreather divers was catastrophic. Some divers kept on diving their Teledyne oxygen sensors beyond the time they should. I know of at least two fatalities because the divers involved were using fuel-limited cells.
However Teledyne’s decision was wholly understandable. The CCR market is miniscule and it was alleged that their entire profits from this sector had been used up in legal costs and the settlement."

While the above court transcripts from the 2008 Egyptian issue would likely make interesting reading, more germane to the topic it is certainly thought provoking reading just how many of the 500 odd known rebreather fatalities https://www.opensafetyglobal.com/Saf...ase_100725.xls were recovered drowned; with the loop floating free....

There's a reason a retainer for the facepiece has been a CE requirement since 2003 in order to both prevent the unit flooding and sinking and the diver drowning when unconscious....

[Chimp]

I’d urge every CCR diver to watch the presentation when BSAC put it up (it was recorded so I assume will appear on the website at some point). It might just change your mind (and save your life). Paul had really done his homework and presented hard data rather than anecdotes to show the difference an MRS can make. Interesting talk though even without the backdrop of MRS promotion.

[Chimp]

Many people cite going unconscious and that a retainer would save you - but miss the point that somebody needs to save you either way.

As shown during the presentation some people have self-recovered after blackout when using an MRS. And this misses the point anyway. You can't be recovered if you've already drowned.

You have to work pretty hard to go hypoxic on a rebreather

At depth yes, but the presentation gave a real-life example of this definitely not being the case in the shallows. Blackout on/near the surface can happen very quickly and with no warning. It has killed plenty, including very experienced divers all the way up to expert.

[Chimp]

Vast majority of CCR deaths are from same reason "not knowing your ppo2".

Vast majority of CCR deaths are actually from drowning. Not knowing your po2 might mean a breathing gas issue and LoC, but it’s very often drowning that is the end result. Paul presented it as chain of events eventually culminating in drowning and showed how we try to break the chain in other places e.g. multiple O2 cells, HUDs, training, checklists, maintenance, awareness or ‘experience’, etc, but we miss the obvious and fairly easily resolved bit about not letting water in. Even with the most diligent training and checking and maintenance and ‘awareness’ the possibility of breathing an inappropriate gas and a LoC can still happen. The MRS gives a chance of recovery when it does (some people have even self-recovered after blacking out and sinking). The ‘will never happen to me’ mind-set is human nature of course. We all suffer from it but if we step back and look at the data, and how easy it is to break the chain and at least partially mitigate the overwhelming cause of death (drowning), then I’m sure many more would be using an MRS.

[Chimp]

I have been using the AP strap for 8-9 years.

I tried the AP one and thought it was crap tbh. It’s cheap for a reason. Basically just a rubber band with a big o-ring at each end. In my opinion this strap is simply to pay lip service to the 14143 requirement. It does not keep water out when the mouth/jaw is allowed to go slack as it would in a blackout. All the (albeit minor) disadvantages without the main advantage of keeping the airway dry during LoC. Equipment like this does nothing to promote the use of MRS as people buy it, fit it, realise it’s crap, then remove it and decide MRS is a waste of time. The only MRS worth using imo is the Draeger one (I think the one supplied by revo is basically a copy). Martin at tecme has them (google ‘tecme strap’). They are €90 and well worth it. It has a pad with a protruding lip that, when properly donned and adjusted, seals against the face and stops water ingress even when mouth/jaw completely relaxed.

The only ‘inconvenience’ I’ve ever really had using the MRS is the drool clearing drill (close loop, remove, stretch above head, shake, etc). My simple solution…drink it! It came out of me so what’s the problem of it going back in? A bit of extra hydration never hurts ;-) I find this a minor price to pay for the safety increase not to mention the comfort of being able to completely relax my jaw/lips on long dives without flooding my unit.

[Vanny]

I think for the drool issue the stretch roll and chase the gunge round into the water trap works just as well if not better than removal and stretch. Works for AP units others may vary.