Explorer CCR by KISS With Mods

[deep thought]

Good eye  and no I do not have a BOV on any of the CCR's that I "actively" dive.  The Poseidon Discovery is an exception, but I don't actively dive the rig...

I am not opposed to BOV's, but I choose to follow a different philosophy on emergency protocol.

When the KISS rebreather was designed, it was built as a recreational rebreather by a diver who had very poor air consumption.  Gordon was looking to build a gas extension device and he succeeded quite well.  His idea was in the event of a problem, twist the valve on BOV and ascend...no convoluted techniques, just bail out!  When he designed the Sport KISS, he designed it exclusively for the recreational market and it also has a BOV.  This has not prevented divers from manipulating his original concept to tech dive and I have had divers on trips to Truk Lagoon dive the KISS past 300 on outer wall dives.  I know cave divers who regularly dive the Sport in Devils system.

The Poseidon Discovery is strictly a recreational diving rebreather, and it has built in limits to prevent a diver from diving with any gas source other than "air" and has a restrictive depth limit.  The BOV is integral part of the system and it will not go into dive mode unless the BOV is functioning in pre dive set up.

All of these (3) units described were/are "Sport Diving" rebreathers that I agree are well suited to bail out as first consideration when confronted with an issue.  A sport diver would be using air as a diluent, or normoxic 21/30 trimix, and either of these gasses are breathable at surface to depth students are certified to.  Assuming the sport diver has not used the diluent cylinder below a safe reserve to bail out, it may allow them to surface or provide time for them to secure a bail out stage. 

The rebreather industry has also evolved a lot in the past ten years, and I have seen many changes in design as well as techniques.  There is a trend towards technical divers adding BOV's to rigs that traditionally did not have BOV's, and certain manufactures have gone to extent of designing BOV's just to meet consumer demand while their foundation was built on a rig that did not utilize BOV.

One reason that I do not utilize a BOV on rigs I dive is the consideration for the gas that is plumbed into the BOV, it has to be breathable.  Since I dive almost exclusively with trimix mixtures below 21% this poses a risk at the surface and shallow depths.  So if I regularly dive 200-300 foot, there should be no concern as depth/pressure makes the gas breathable....but depth is not the danger zone with a ccr, the surface and shallow water is where ccr divers must be the most concerned.  At depth if my BOV is plumbed into a diluent cylinder, I can bail out and get 3-5 breaths before the cylinder is empty? Well this is obviously not a workable situation as any emergency whether it be Co2 or coughing on swallowed water will take 10+ breaths just to get settled!  So my only option then would be to have a whip with some convoluted plumbing gas switching block or stage bottle plug in.  And there is nothing I like less than weasels in dive politics, is a convoluted rebreather.  I like rebreathers to be simple (Keep It Simple Silly)

If you look at any technical manual on oxygen, you are likely to see a chapter on oxygen toxic reactions, PPO2 recommendations, NOAA time limits, the authors idea of conservative oxygen exposure limits, signs-symptoms, etc... and perhaps one sentence or paragraph on Hypoxia - maybe?  So the age old demon of "high oxygen is going to kill you" is so embedded into the technical community that divers are not well enough informed of the true danger of ccr's "Hypoxia"  I was fortunate to be on a couple dive charters where Dr. Grant demonstrated live demo on hypoxia (on his KISS CCR) while aboard the Nautilus Explorer, and since then I have seen one diver go hypoxic, have lost numerous colleagues, and have had students report to me recent experience on surface while entering water... then I had my own recent experience while putting a subsurface float on the new wreck Doty (shallow water).    My teaching has been modified by 15 years of actively diving ccr's around the world, by the deaths of friends and colleagues, and personal experiences with hypoxia. 

While I do respect Oxygen Toxicity, I consider Hypoxia the Grim Reaper that is going to get you if you turn your back on it.  Almost all of the skills that are used by two training agencies I work with are based on the first CisLunar that is 20 years old and no longer in service.  The dreaded "Stuck Open Solenoid" is one example of what was driven into my psyche as an early instructor, and there are skills we present to stop this and continue bailing out on ccr, even on rebreathers that do not have a solenoid?  This is only one example.  Another popular rebreather is responsible for the term "If In Doubt, Bail Out" and the AP Diving rebreather had a Safe Second Inflator where divers are trained to take 3-4 "Sanity Breaths" then return to the rebreather - flush - and try to resolve the issue.  So training agencies adopt IIDBO for all courses, and try to do this with a rebreather that does not have a diluent flush like the KISS... you bastardize some method of getting gas into the ccr, but you are fooling yourself in a half-hearted attempt.

If you are lucky to get any signs of an impending doom, then you have to have enough cognition to make "only one response" and that is your choice as a diver to decide: what one action will always be correct at any depth to save my life??  I enjoy rebreather diving and unlike people who go out of their way to make a rebreather some anal practices that requires divers to labor hours on set-up, break-down, cleaning.... I go diving and have hundreds-hundreds of hours on multiple ccr's.  Rebreathers are not rocket science, they are not difficult to dive, maintain, or be safe.  Rebreathers are what you make them, and habits are what keeps you alive. 

My choice of "only one response "is If In Doubt Flush It Out" then look at your PPO2 or try and think if there is something wrong.  If you have flushed a ccr, and this sounds simple, but I have seen many divers who do not understand the proper way to flush a ccr (not same technique on all ccr").  But if you do know how to effectively flush a ccr, then you will buy the time you need to make a life saving second step - either fix the problem or bail out to off-board.  Get your brain some good gas - shallow or deep - then you may have a chance to survive and "incident".  Like my near surface hypoxic event, I suffer from the same hypocrisy that all humans struggle with "denial" and not doing what I preach to my students.  Flush First then think second, but NOOOOO I look down and see PPO2 of .13 .14 .14  at same time I flush.  People fight to stay alive as proven by mountain climbers that keep on climbing, accident victims that try to get up, soldiers that are shot that keep going...we simply do not want to accept that we could be dying and unfortunately by the time you recognize hypoxia it is too late.  When struggling to breath, or absorb enough oxygen, the human instinct is to spit out the mouthpiece as it is foreign and to swim to the surface because our brain knows we should not be underwater!  So your human instinct and response is only going to make it worse!   

Face it, that you can only train and repeat a few skills that will stick with you, and you are better to focus on only one technique that you will embed into "Muscle Memory" than two or three that will be muddled when your brain does not have enough fuel to make conscious decision. 

At or near the surface jam the oxygen into the loop - you can never have too much oxygen at the surface

At depth jam the diluent

You are only making one decision, am I shallow or am I at depth?  And your ccr should be equipped with manual injection that is simple and Please Do Not put isolators or shut off valves on emergency flushing gas! That is equal to putting a safety shut off switch on your automobile air bag system - Hey a car is going to hit me head on "BAM" too late... There is no reason to put shut offs on any gas, with exception of your High PPO2 off-board stage (keep the reg pressurized and you don't deploy without reason).  One of the reasons that I like the Titan Gas Block on KISS / rEvo is the one hand reaction to hit either oxygen or diluent for flush, but I am muscle memory trained to flush on Meg, Inspo, Optima as well. 

So if you have a BOV that is smaller than a Volkswagen Beatle, then I have no problem.  I have used the KISS, Poseidon, Golem Shrimp, AP Diving BOV and all I can say is that the BOV must be a "One Hand" operation that you can do with half a mind...if not your are fooling yourself.  If you have to plug and un-plug, swap fitting, or switch a gas block then it is only a piece of mind only comfort. 

Always challenge conventional wisdom, and don't let your eye off the ball as it tends to rolls away.

Ron