| Every year, in all the navies
with O2 CCR divers, several divers experience underwater
oxygen-induced convulsions. All of them probably are
still alive and perfectly healthy, doing the same job,
because their buddy brought them up at the surface with
the mouth-piece secured in the mouth with a strap around
their neck. They did not get water in their lungs. Years ago I witnessed an accident. A CCR diver swam a little apart from his buddies and some seconds later when they looked for him, he was drowned-dead, with his mouth-piece closed floating above his face and his open-circuit bail-out second stage freed from its bungies on the bail-out tank but not in his mouth, hanging downward. He suffered an oxygen hit for reasons that are not of our concern here, probably felt it at the early stages and so closed his mouth-piece before reaching his open-circuit bail-out second stage. He never had time to put it in his mouth or spit it off when convulsions started. Then water flooded the lungs. So there are two things that I considered as absolutely necessary for surviving difficult times with a CCR : the strap holding the mouth-piece around your neck and the integrated bail-out open circuit second stage in the diluant supply valve, aka bail-out valve (BOV).This is my personnal opinion and others do not agree. You should take the advices from your CCR instructor. A discussion can be raised on where to connect the OC : on the 3L CCR in-board diluant tank or on the bail-out 7/10 L tank. Both have pros and cons. Keep in mind that the point of a BOV is to enable you to perform two tasks in one single move. First to breathe a few times (sanitary breathes of Dave Thompson) without putting your mouth in the water and second to close the CCR loop before switching to the bail-out reg. When hypercapnia sets up, there is no way you can take off your mouth whatever you have in it to breathe from. But you can turn a valve. Also if you "faint" from hypoxia or convulse from hyperoxia, your partner can turn the valve and then know what you breathe . IMHO, a BOV is a life-saving necessity. |
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| Several models are available, on the market : - DIVEMATICS in USA ; - JETSAM, in Canada, but you usually have to buy the whole rebreather around the mouth-piece ; - BOB HOWELL had build one, in England, but it does not seen available any longer ; - the HALCYON's one; - and the FK BOV that I bought (2002) from Filip Krolak , in Poland. DO NOT DEAL WITH FILIP KROLAK ANY MORE - HE TOOK MONEY OF ABOUT 10 PEOPLE WITHOUT SENDING THE MOUTHPIECE ! - There is a recent model (2006) that seems to be very silmilar to the FK one, done by GOLEM GEAR . - A BOV also very similar to the polish one of FK is now sold in Germany by V4TEC and people seem happy about it as you can read in the rebreatherworld forum . - and now (2008), aT last, AP VALVES is about to provide one for their CCR. Check regularly their web site because they have been about to provide one for almost two years). - and probably others that I am not aware of. |
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and here in the water : ==> |
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| Stéphane Havard - October 2002 | |
| additions in July 2008 | |
