Category — BOV - DSV

What I like and what I don’t like – A personal view 

I bought my first Inspiration e-CCR Rebreather back in 1999 and back then there was no choice between Classic, Vision or even the Evolution. It was plain and simple the Inspiration, now known as the classic version of a range of Rebreathers offered by AP, and manufactured in the U.K.

As it was my first Rebreather I ever purchased the choice, and my knowledge about choices, was rather limited back then so I had not much to pick from in terms of other units commercially available to the public … or at least I was not informed enough to know about them. The unit was purchased in Singapore by a friend and then came to Mexico. I did a number of deep cave dives on the unit and sold it about 3 years later to a friend residing in Utilla, Honduras where I believe the unit is still up and running. 

Late last year I took the chance and offer to purchase a used Inspo from a friend of mine who was willing to part from his Vision Inspiration e-CCR Rebreather with only about 40 hours on the unit. The unit was living in Canada at that moment. When the unit came to Mexico it was in a still spanky shiny new turtle box with no scratches on it as the unit was housed during its 40 hours in a aluminum travel frame. 

The things I like on the Vision & what I left as is

Decompression capability - I am actually an advocate of having the dive computer and Rebreather separated but have to say that it is quite nice to have the decompression computer tied into the actual Po2 from the sensors. My CCR capable dive computer (Liquidvision X1) is the primary dive computer and the inline Vision decompression computer housed within the handset my backup.

Handset - I like to be able to put the handset on the wrist as on the classic they were hanging somewhat below my profile and dragging in cave sediments a view times. To have only one hand set on my wrist instead of two is quite nice as well which leaves space on the other wrist for my CCR capable dive computer. 

Sensor changing and placement - They changed the design of the head and now you can actually change the sensors without breaking any water sealing o-rings and need no tools anymore in order to do it. The way the sensors are connected now is better as well as on the Classic Inspiration where corrosion and conductivity issues frequently plagued my diving excursions. They changed as well the metal battery housing screw who is now not located directly opposite the second sensor anymore and does allow the unit being laid on its back without condensation water droplets dripping directly onto the second sensor. 

Tempstick - I have to say that I like the temp stick display even if I do not use it as a reference on how long I can still stay and use the absorbent.

Hydrophobic membrane - I like the hydrophobic membrane on top and bottom of the absorbent cartridge which gives a bit of protection to the absorbent in case we have some water in the can. 

Calibration - I got used to it how easy calibration is on the unit.

HUD -I like the HUD even if the placement is not entirely right for me … because of my big head. I guess. 

The things I do not like on the Vision & what I changed

Softpack – I do not like softpacks with all of them straps and plastic buckles. After all these years of cave, wreck, tec as well as dry suit diving I have to say that I do prefer a stainless steel backplate with all through standard webbing and a sturdy crotch strap. With the use of my standard Dive Rite ss backplate I have all the d-rings exactly where I want to have them, and can use the same backplate for oc and cc diving. This is one of the modifications to make the unit right for me. 

Wing – The original box wing I do not like. With the softpack went the original box wing which was replaced by a Dive Rite 55 lbs Rec wing, but can be changed for any brand, any size wing either single, double or sandwiched. This is one of the modifications to make the unit right for me. 

The inflator and bailout regulator – With the old box wing went the complex and prone to leak (at least mine) inflator and second stage assembly. Not only did I have some leaks but it was hanging below my profile and is in the way of streamlining myself. It makes deflating and sharing gas with another diver at the same time a bit more challenging too. I am an advocate of having my CCR and my bailout gas separated so I am carrying always a separate bailout tank with me. This is one of the modifications to make the unit right for me. 

DSV – I did not ever like the original DSV. Somehow I had a problem to remember which way is open and which way is closed. From my prior CCR diving experience I came to like a BOV quite a lot and it was a much welcomed change on the unit. My BOV is attached to the inboard diluent tank. The BOV access to the diluent tank is only a step in-between in my bailout procedure. It allows me to get off the loop very fast and convenient while I am getting my bailout regulator ready. On deep dives I change to larger onboard diluent tanks. The BOV allows my dive partners intervene externally as well in case I am unconscious or behave erratic. I attached a Golem Gear BOV to the unit. This is one of the modifications to make the unit right for me. 

The box – The yellow and black plastic container I do not like. While traveling a lot I found the large plastic box a bit too cumbersome. The other aspect was that I had to drag half of it around to get my countelungs disinfected. The cover in my point of view has the potential disadvantage that it can trap gas bubbles underneath in case of a leak with either O2 or diluent, quite a bit of gas actually. I first changed that while drilling little holes into the cover. In the end I placed the unit into a steel frame which did a couple of things for me. The ability to travel light and disassemble the unit into individual pieces, to change the backplate and wing fast with any brand and size, as well does the frame allow for a wide variety of back plate and wing mounting positions helping with trim. The open design of the frame I use does allow my dive partner to see all components of the rebreather in order should a leak arise, as well the amount of gas that can be trapped below the cover is very minimal. This is one of the modifications to make the unit right for me. 

Non-detachable counterlungs – Pain in the butt to keep clean and dry. Keeping the unit sanitized seemed to be a drag literally as I had to drag the plastic shell with me to the water source and then somehow place it in a way so the lungs can dry while on the floor or table. I live in a humid environment and want to hang my lungs up to dry, so I cut them off the attachment point and sewed on a d-ring each on top. The top of the lungs are now attached via a quick link to the frame while the bottom part is attached via bungee and a clip to my crotch strap scooter d-ring. The counterlungs are not attached in any way to my harness to allow me to move them around to get to my backup lights, d-rings for bailout or stage tanks or my dry suit inflator. This is one of the modifications to make the unit right for me. 

Tank size restriction – The original plastic box allows only one tank size with one particular valve design to be used. As I travel a lot I may choose to travel with small aluminum tanks or don’t pack tanks at all as I rent tanks at my destination. As my destination provider may not have the tanks I like to have the plastic box is limiting me in my choice of tanks. With the steel frame mounted to my unit I can use Alm 13, 19, 30, 40 and 80 cft tanks mounted to my unit as well as 2, 3, 4, 5, and 7 ltr steel tanks. This option is quite useful when traveling. This is one of the modifications to make the unit right for me with the installation of the steel frame. 

Special sensor – I do not like the fact much that I do need special sensors for this particular unit but another sensor for all my other units which puts me into a situation that I need to stock two different sensors. However, with the new connector a lot of my old sensor connectivity and corrosion issues have been addressed, and all I can do it stock special sensors for the Vision. 

Plastic buckles – I do not like plastic buckles and fast clips at all. In my experience they break way too many times and always at the wrong time, the time I am ready to go diving. With the change to an ss backplate with standard harness and ss buckle this issue has been addressed. With the counterlungs now detachable and connected with metal quick links and clips got me to get rid of all plastic attachment points. This is one of the modifications to make the unit right for me. 

The things that don’t bother me much on the Vision 

Plastic bucket – The bucket where the absorbent cartridge is living inside is made out of plastic but has hold up very well so far including the metal threading embedded in the bucket walls. On the Classic Inspo you could actually rip them out while over torqing the screws that hold the lid on the can but with the Vision you have them little black rotary clips with a lesser or no chance to rip out the metal thread rods.

Single o-rings – The unit is been designed and sealed with single o-rings in all locations only while other Rebreather manufacturers are using a double o-ring design with at times large and thick diameter. So far I had no problems and the unit is tight with excellent positive and negative checks.

Mesh webbing over counterlungs – The new counterlungs have a partial mesh webbing over the inner and actual counterlungs. Especially in cave diving sediments can fall in there and with a lot of time and rubbing action can damage the inner counterlungs but I have had no issues so far.

Battery life – The battery life is not too bad, could be better but could be worse too. I run the unit fully electronic and just carry extra batteries with me. Fortunately they are readily available in most photo stores anyways. 

All in all I am quite happy with the unit after I have done the changes as outlined above. The unit is streamlined, light, is reliable (at least my electronics are), has a very good horizontal trim now with the changes done and is user friendly … at least for me.

Greetings

Matt

A Bail Out Valve (BOV) is a Diver Surface Valve (DSV) that has a second stage regulator incorporated into the mouthpiece and is connected to either the onboard diluent tank or the off board bailout tank thus supplying the diver with open circuit breathing gas. A rebreather diver who is using a BOV is either on the loop breathing of his rebreather or on the regulator breathing open circuit enabling him to have a breathing source at all times.

There is a variety of BOV’s on the market now, some rebreathers are coming factory equipped and stock with a BOV while others can be fitted with aftermarket BOV’s. Most BOV’s have a drum within the mouth piece and when turned allowing breathing gas upon inhalation either be taken in from the rebreather or the open circuit regulator. Some BOV’s are very sophisticated with magnetic switches inside actually allowing the electronics to see if the diver is on the loop or on open circuit.

BOV fitted onto Megalodon loop

Why or why not to use a BOV seems to be a personal preference until you look a little deeper into it. Of course the opinion expressed here is my personal one but has developed through time while witnessing first hand events that could have been handled better with a BOV or hearing from other divers what happened to them. What I have witnessed over and over again is that divers do hesitate to long, way toooo loooong before they decide to go to bailout when they think something is not right. They start thinking about it, are not sure, they feel something is or was not right, don’t want to be embarrassed or think the process of bailing out is just to cumbersome and time consuming. The installation and use of a BOV does change that and can be a life saver.  

It has happened that a diver managed to get in the water without Co2 absorbent in his unit, despite checklist and all that. As they went down at about 20 feet / 6 meters the diver was breathing uncontrolled due to exertion and very high Pco2, experiencing extreme hypercapnia. The dive partner realized what is going on and urged the his friend to switch to o/c. The unit was not equipped with a BOV. The diver was not able to make the switch as he was not able to hold his breath for even a split second to do the switch over. They went back up to the surface and both lived to tell the story. With a BOV the diver would have been able to switch from his rebreather to his o/c bail out without a problem and without the need to take his mouthpiece out of his mouth. Additionally the other diver could have intervened and help the affected diver while turning a simple knob on his friends BOV mouthpiece, helping the distressed and potentially incapacitated diver.  

Something else I have witnessed with BOV equipped divers is that they tend not to think much about what gas they have in their BOV supply tank and use the BOV freely on the surface, and why not. It is that I just somewhat uncomfortably imagine as they go on with their diving career and coming to trimix diving that this habit will have them killed on the surface due to potentially hypoxia breathing a low o2 content hypoxic breathing mixture on the surface, possibly exerting while moving along the surface toward a down line or trying to catch up with a boat or drift line. As one habit might be good in one diving situation it may kill you in another.

Shall I connect the BOV to my inboard diluent tank or to my off board bailout tank. Well, that depends on the depth you want to dive at as usually your inboard diluent tank is rather small unless changed to a larger tank to allow such move. My thought is a bit deeper though. I believe that if I decide to go off my rebreather (SCR or CCR) then I am off and want to go to something that is not connected at all to my rebreather because my rebreather is my rebreather and my bailout is my bailout, separated entirely and not connected to one another. Personally my BOV is connected to the inboard diluent tank.

two Megalodon divers fitted with BOV

When doing that last switch over to your complete detached and separate bailout gas supply, you as well have decided you are not going back onto the rebreather as you have decided you do not trust it anymore, or it does not work anymore other then providing buoyancy. And you stick with it. And while you are at it change your set point to a low one or manual, open the over pressurization valve from your counter lungs as you will go up and if using electronics or dive computers with ccr - o/c capability do the witch there too. The BOV could be a life saver if used properly.

BOV on KISS diver

I have seen some divers who had their BOV plumed via disconnect into their o/c bailout stage tank and this way going onto your BOV you will not need to take the BOV out of your mouth to go onto your off board bailout tank, keeping your mouthpiece in your mouth to do a easy switch over and yet go off your rebreather onto a separate tank at once. That is fine if that is what you want to do but as I am feeling strongly about team diving I would still need to have a second stage regulator connected to my bailout tank in case my team mate is in need of bailout gas.

BOV on P-SCR diver

With the limited volume offered by the onboard diluent tank the BOV is just an important step in-between to get off the loop and then onto the separate bailout tank (I will discuss other than o/c bailout options in a future post). While taking a breath or three while on my BOV connected to my inboard diluent tank I have time and a controlled breathing gas while looking for my main bailout tank regulator, then go on to my large o/c bailout stage, which is a completely separate life support system with pre-calculated Po2 and gas volume.  

If you just think about going off the loop and to bailout but cannot even put your finger on what or why, that very thought of just thinking about bailing out is the very reason to bail out, now. Do not hesitate a split second and go to o/c bailout, because that might have been your last chance to do so. The installation and use of a BOV can be a live saver. I currently have a BOV on almost all my rebreathers using a Golem Gear BOV on my CCR Megalodon and Inspiration, and manufacturer BOV with Classic KISS as well as P-SCR. The only exception being my CCR O2ptima who does not have a BOV, but I am sure thinking about installing one. In deep diving with higher Pata and with it higher Pco2’s or in cave diving when dealing with navigation in case of a breaking through, the fast need to switch over to bailout might warrant the use of a BOV with the added ability of your team mates to help and intervene if you are possibly incapacitated by hyperoxia, hypoxia or hypercapnia.

Matt