Just sat in on an interesting BSAC webex on rebreather safety and wondered how many rebreather divers are using a Mouthpiece Retainer Strap?
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Just sat in on an interesting BSAC webex on rebreather safety and wondered how many rebreather divers are using a Mouthpiece Retainer Strap?
Mouthpiece retainers are in my opinion completely pointless - over 100s of personal hours and many rebreather students I have notice you are much more likely to need to get loop out of your mouth that you are to need it kept. Many people cite going unconscious and that a retainer would save you - but miss the point that somebody needs to save you either way. You have to work pretty hard to go hypoxic on a rebreather and it'd be much better to develop skills and awareness and dive in a better team than put a strap on your mouth piece.
My rEvo came with a gag strap & initially I hated it but came to love it. Grahams point is very well made though it does take more to remove it safely without your mask being ripped of at the same time by somebody trying to save you.
But I dive solo 99.9% of the time & with a BOV. If I fall unconscious well maybe I wake up maybe I don’t but I won’t drown !
Anytime I dive loosely with a buddy the instructions are to turn the BOV switch & hope I come round before the gas mix becomes hypoxic
Very good thought provoking presentation, not really anything I could disagree with in there. I may consider a strap but it needs to be effective.Quote:
Originally Posted by Chimp
I have been using the AP strap for 8-9 years.
If correctly adjusted it holds the mouthpiece just where I need it, and there is no need to bite on the mouthpiece to keep the loop in place.
The AP BOV is quite bulky. When scootering without the strap I occasionally found my jaw ached. With the strap there is no such issue.
If I became unconscious, and ended up lying on the seabed, I prefer to consider there might be alternatives other than just sending me to the surface.
Without a gag strap I'd be a light source, lying on the seabed, with a small stream of bubbles coming out of the mouthpiece. That is not a good image.
All the smug Revo divers voting :-)
I know very little about diving CCR, but I definitely am very happy with the gag strap in place. To remove the mouthpiece when the strap's tight, it rolls out of the mouth pretty easily for bailing out; rolling it downwards just after switching the DSV (which on the Revo is a lever that's moved downwards).
Regarding the presentation - very good, very informative - a lot of the problems seemed to be rooted in not being aware of what's going on, such as monitoring PPO2, old kit, etc. No question that having decent computers - main Petrel and backup Nerd means you've got all the info where you need it.
What do you need to remove the loop for Graham?Quote:
Originally Posted by graham_hk
I use a gag strap and BOV and wouldn't feel comfortable without either now. At least with both, whoever you are diving with can easily be instructed to just flip the lever in the event of an unconscious incident.
No risk of flooding the unit during a switch, no fumbling for a second stage etc. during a rescue.
In both live bailouts, I've experienced I've been able to stay on the BOV to the exit point.
I use draeger one. I'd still use it even if there were no safety benefits as I find it comfortable.
Graham what possibly gives you the idea that a retaining strap makes it difficult to get the loop out of your mouth? These things aren't lodging the bloody loop right into your gob like something from the S+M shop.Quote:
Originally Posted by graham_hk
The mouthpiece being retained in a LOC event (hypo or hyper or co2...) has best chance of saving you. Yes you still need rescuing but the odds of that being successful are massively improved (from the near-zero chance without one!)
Vast majority of CCR deaths are from same reason "not knowing your ppo2". Nothing to do with old kit, wrong computers anything like that... plenty people with latest electronics etc died because they did something which led to them not knowing their ppo2 be that borrowing a mates unit with years out of date cells, forgetting to turn unit on, forgetting to turn o2 on, silencing a cell warning 3 times.... etc. etc. etc.Quote:
Originally Posted by Wibs
(lots of them right near the surface too... I always run my unit as near to pure o2 as possible when near surface, don't need any monitoring at all then, in fact my first home build didn't have any electronics at all. Would definitely recommend trying that, teaches you a lot)
Makes sense when you remember Graham is likely to dive his JJ in the GUE configuration, which the questionable addition 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 :rofl:Quote:
Originally Posted by 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.
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.
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.Quote:
Originally Posted by Vanny
He specifically said about removing the loop from ones gob!Quote:
Originally Posted by dwhitlow
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.Quote:
Originally Posted by WFO
Quote:
Originally Posted by GUE
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)
https://xray-mag.com/content/john-la...2%80%94dies-78Quote:
Originally Posted by WFO
"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....
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.
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.Quote:
Originally Posted by graham_hk
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.Quote:
Originally Posted by graham_hk
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.Quote:
Originally Posted by WFO
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.Quote:
Originally Posted by dwhitlow
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.
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.
The kit comment was more about where the 'computers' are. For example an old handset will be harder to read than a wrist-mounted OLED display, or an eye-mounted Nerd. One thing I've found is even though there's a Nerd display in my eyeline, I have to constantly remember to look at it, particularly when a lot's going on, e.g. bag-up ascents. Would imagine that a set of HUD flashing lights would be the same where your brain filters it out (like adverts on a website).Quote:
Originally Posted by WFO
The not knowing your PPO2 really does seem to be a recurrent theme.
I'll have to hunt down a link. I've thought about one for a while but I have a bit of an overbite and a wierd-shaped head, so couldn't ever get one to sit comfortably for long.Quote:
Originally Posted by Chimp
Ok but if I fell off my motorbike and smashed my skull into a road sign they'd say I'd died falling off my motorbike rather than from hitting my head on a road sign...Quote:
Originally Posted by Chimp
And most folk would just say "he drowned while diving" rather than "he didn't know his po2" ;-)Quote:
Originally Posted by WFO
Ultimately I think it will take the efforts of the instructor cadre to bring about the change. I believe at least one training agency (RAID?) are now going to promote the use and this would be a major step forward. Problem is the main drawback that is often cited (not being able to take the loop out easily) is something that’s probably done most often during training.Quote:
Originally Posted by jturner
There is lots of extra ‘faff’ when learning CCR though but it’s just accepted as part of the learning process and we do it because it helps to mitigate the risks. The MRS should just be another part of rebreather diving ‘faff’ imo. The analogy given during the presentation was that of seat-belts use in cars. A lot of resistance when they were made mandatory but the death rate plummeted and now nearly everyone just puts the seat belt on automatically without question. If this sort of culture change can be achieved with MRS, where we look back in a few years and ask “did people really not use these?”, then I think quite a few lives will be saved. I strongly believe there are people who would still be with us now if they had been using an MRS.
GUE ran an article on this, Andrew Fock's comments are particularly interesting.
https://gue.com/blog/gag-me-with-a-s...rs-and-safety/
pH same guy that knocked out the apox user manual . Lol a joy to read . I'm outQuote:
Originally Posted by JonG
When they say military divers ? That be the O2 rigs
That operate in teams and never deep or long deco .
Yes a fair point but for us with an interest in not getting dead our selves then the drowning is the "road sign" i.e a passive thing you happen to run into when you loose consciousness without a gag strap/FFM and timely rescueQuote:
Originally Posted by Chimp
As someone with pertinent experience (MOD1 in July 2020 on a Revo with no previous CCR experience), there's simply no issue with the gag strap in removing the DSV for bailout. It's 'rolled' down and out. For the hero loop clearing, the strap's loosened, slid off the head and the loop held up and shaken. Once done, the loop's put back in and the strap slid over the head and tightened.Quote:
Originally Posted by Chimp
Your going to need a 2nd gag strap to take the strain of all them nerds you have Blocking your view..Quote:
Originally Posted by Wibs
Don't know if it's the same presentation but I saw a similar one previously. At the time I decided to give a MRS a try. Took a while to find one, eventually settling on a rEvo one on my JJ. Once I started using it I liked it especially on long hangs as it just took the weight off my jaw. Not a total convert though. It can be a bit a faff with a hood. I found getting the mask strap and MRS strap comfortable a bit of a hassle. So I started to go with the mask strap under the hood approach. Would agree with the comments above. For general dives I would use one, however if it's a training dive that involves lots of bailout or mask skills I wouldn't.
I use the Draeger one with a Shrimp, either over a hood in OW or in OHE it still fits over my helmet even though it has two side mounted torches on it.
Couple of observations using it.
If the strap is too tight it seems to encourage a relaxation of jaw muscles and soft palate and you can get a bit of a disconcerting snorting sensation, which engages your nasal passages and collapses the mask. Took fucking ages to work this out, but with a slightly looser strap and tighter bite it's very comfortable.
It's easier to fit before you get in, but this encourages a discipline which avoids immersion of the mouthpiece prior to submersion, which could occur when the valve is open to the loop or allow detritus in that can and has compromised non-return valves in other documented incidents.
You are less likely to remove the mouthpiece in water on surface too, so less risk of inadvertently flooding the unit waiting for pick-up.
Ouch! I think that's a bit harsh. Not being up to your standard on technical writing shouldn't diminish his presentation on CCR safety. We all have our strengths and weaknesses after all. Maybe take the time to check his credentials, and have a look at the presentation, before deciding to dismiss the message? What does it matter who the messenger is anyway if the message is sound?Quote:
Originally Posted by gobfish1
Military diving involves much more than just O2 sets (if you take the time to view the presentation if/when it becomes available you'll see this). Besides, what difference would that make anyway to the message about MRS?Quote:
Originally Posted by gobfish1
And the 8-10hr dives using submarine launched SDVs mentioned in the webinar sound plenty long enough to me! (they were mentioned by the presenter as he said he was able to sleep for a few minutes at a time during these dives without drowning by means of correct use of the MRS).
The other reference to military diving was a study of French navy CCR divers where in over 50 LoC events only 3 drowned. All were using MRS.
I think the gag strap will go the way of the bail out in that at the start most people were diving Alpinist and either not carrying bailout or carrying enough. I can recall doing 40m dives on a unit with a 3l bailout.
Now if you even suggest going diving on CCR without at least an ali 40 then you are considered crazy.
Ive been using a gag strap for a couple of years, ok, it took a while to get used to, but Im comfortable wearing it now.
I did take the time to read them the first time round .Quote:
Originally Posted by Chimp
And I know Paul's back ground and so called credentials.
If sleeping on the job is something people aspire to
Then don't let me put you off
Lol his technical writing . Red head would shit a apox per packed be4 he would let Paul do something
technical.
As do I (and there's nothing 'so called' about them).Quote:
Originally Posted by gobfish1
I have no idea what yours are though, but would still extend the courtesy of listening to what you had to say before making any judgements.
I won't ;-)Quote:
Originally Posted by gobfish1
Bear in mind that the success rate of that French study of Naval divers, should be viewed in the context that each diver in the French study was TETHERED to their buddy. And I don’t see much tethering going on in technical diving...but, I still recommend using the gag strap and BOV!
Sent from my iPhone using Tapatalk
Very true. A good point (and one that was made in the presentation). Even with a tether though how many would have survived if the loop had fallen out? Quite a few less I would suggest.Quote:
Originally Posted by cathal
No judgements just to meney years reading shite posted on the inter webQuote:
Originally Posted by Chimp
Paul's a nice guy so I'm told ( read a few of his papers over the years even liked them. ) Shot him self in the foot with his Deas and Pox connection.
Some just need a drum to beat . Others a stunt dive .
cmon gobbers you must have a copy of that report from a british diver filed away that you can share.Quote:
Originally Posted by Brad_Horn
my memory sometimes plays tricks on me so I may not remember it all but in summary I seem to recall a forum post along the lines of 'oh my god, oh my god, I was going to die. martin why did you do this to me? it's all your fault', or am I thinking of a different incident?