A Comparison-Contrast of Available Rebreathers

[Gill Envy]

How to compare and contrast the available rebreathers on the market is an eternal question and the answers are constantly evolving with changes in market trends. Few people really want to answer this question because few people own all the rigs. I am by no means a authority on the subject but I have owned two very different types and gotten some hours under my belt. I have put some time and energy into explaining the major differences as I have observed them. This list is not comprehensive, is not all first hand knowledge… but I thought it might be helpful to folks just starting on the path of gathering knowledge. My hope is that this list gets added to. Corrections are also welcome.

There are two main differences between available CCR's. there are those that require manual o2 addition (mCCR's) and those that rely on an electronic set point controller with a solenoid to monitor and inject o2 in the loop (eCCR's). Manual vs electronic only refers to the o2 injection as manual injection rebreathers are becoming more and more electronic with in-line deco, HUD's (heads up displays) and more integrated electronics, but continue to adhere, with near religious conviction, to leaving out the solenoid/ automatic set point controller. To ease the injection process a constant flow orifice or “leaky valve” is used to administer some o2 into the loop, requiring the diver to “top off” with manual injection to keep up with metabolism. It would seem that the trend in mCCR's is not so much in maintaining overall simplicity anymore but rather continuing to require the user to inject o2 manually and continuously monitor the effect of injection and metabolism on the loop’s po2.

Many of the firm believers in mCCR's have concluded that manual injection builds safer habits, as monitoring and adjusting loop o2 balance becomes deeply engrained in the diver, reducing the likelihood that a malfunction would go unnoticed. This conclusion seems to be supported by the near zero fatality rate associated with them, though the reasons for this low rate have yet to be determined. Many users simply like the fact that they have a better chance at finding a remedy for in field repairs since they are simpler, reducing the prospects of missing dives or whole dive trips.

The firm believers in eCCR's like the convenience of a set point controller, and often believe that it is a safety net in case of getting over task loaded or distracted. Eccr's seem particularly attractive to photographers and deep penetration wreck divers and cave divers, those for whom hands free function is a high priority. For reasons yet to be determined, there are many fatalities associated with eCCR's, which could reflect their added complexity, additional failure points, their tendency to tempt an "auto pilot mentality" or other factors yet to be determined (more people dive eCCR's, dive them more aggressively, possible need for changes in training standards, etc. etc.). the best attitude to take while diving any rebreather is that you are 100% responsible for what is happening.

The major contenders in the mCCR camp are the KISS, the Copis Meg, the rEVO and the Pelagian. the main features of destinction as I know them:

-The KISS (the name taken from the military acronym Keep It Simple Stupid) is built with a philosophy of simplicity and independence in components. The KISS is responsible for popularizing the use of a constant flow orifice. It has 3 independent po2 only displays, one for each cell and each one is fully independent with it's own battery...no shared wires. It has back mounted, internal counter lungs (not ideal for bueyency or WOB, but reduces clutter to the chest). the KISS has non-pressure compensating first stages, which means it is depth limited in it's stock form, though this can be overcome with outboard o2 for the deep part of the dive. This can be the case for all non-depth compensating rigs. The reason for the non-depth compensating first stages is to help keep po2 relatively constant as pressure increases with depth.


-the Copis Megalodon is identical to the standard eCCR version except for the electronics...front mounted counter lungs, solid build, very modular. The Copis head/electronics come stock with a KISS style constant flow orifice. It has several standard threaded ports which makes it very amenable to mixing and matching electronics from other manufacturers. The electronics that come stock are not fully independent, the displays share a case and the battery. In it’s stock form it is assumed that the diver is diving only to recreational depths with adequate bail out…additional redundancy is recommended to go beyond recreational limits. it has a non-depth compensating first stage, which means in it's stock form it is depth limited, again that depth limit can easily be overcome with off board o2 with a depth compensating reg to be plumbed in for the deep part of the dives.

-the rEVO has back mounted counter lungs, a unique electonics interface that is designed to reduce failure points. One of it's destinguishing characteristics is that it contains two scrubber sections, designed to reduce the chance of breakthrough. It has non-depth compensating first stages. There is also an eCCR version...the rEvo dream.

-the Pelagian has broken from the mCCR pack and offers a depth compensating first stage and an adjustible needle valve...allowing the diver to adjust, on the fly, the 02 flow to allow for changes in depth/pressure making it presumably appropriate for diving to practically any depth. it also has a unique front mounted counter lung design that boasts ideal trim. Many of it’s components are claimed to be readily available making service more convenient world wide.

-there are several electronics packages that are being offered by third party manufacturers that are often used to create added redundancy or replace the stock electronics altogether. The Shearwater, Hammer Head electronics, Universal Rebreather Monitor and VR3 are all third part electronics that are commonly used with eCCR's and mCCR's. Third party computers are often used with a 4th cell, for additional redundancy.

The rebreathers that I am familiar with in the eCCR camp are the Inspiration/Evolution with vision electronics, the Megalodon, The optima, and The Prism. One of the main distinctions among eCCR’s is weather they include truly independent handsets and weather they come stock with in line deco computers. The main features of distinction among brands as I know them:

-The Vision electronics are often referred to as the crem de la crem of eCCR's...the most complex and sophisticated of them all. They apparently dominate the current market. The main difference between the Evolution and Inspiration is size and duration. The inspiration and Evolution come with proprietary valves and a hard case, requiring brand name tanks and valves if used in the stock case, though there are third party frames that open up the options so that you don’t have to travel with the tanks. It comes with a temp stick to help confirm scrubber duration, a HUD (heads up display) and buzzer to help confirm proper set point controller function, onboard deco and a somewhat independent set of controllers. They require annual factory maintenance, and being more complex, it's usually back to the manufacturer for fixes as well. They can be costly to maintain but offer state of the art performance and impressive customer care. They have an apparent low mortality rate associated with them, at least the Vision version though it’s hard to determine mortality rate with any rebreather brand because all manufacturers unfortunately hold on tightly to total sold unit numbers and mortality figures. The original classic version is often referred to as the YBOD, or yellow Box of Death as many people perished while using them. One of the big suspected culprits of the classic was the excessive tolerances in the scrubber…allowing for co2 bypass.

-the Megaladon has front mounted counter lungs, a po2 set point controller, no on board deco. It boasts tank like build quality and devoted customer care, even assistance with in field repair. It comes with a HUD for po2 monitoring. Built to not require a cover, the meg is becoming legendary for it's modularity, allowing the diver to choose everything from the type of electronics to the type of wing, to the size and type of tanks and scrubber size and the list goes on and on...not an easy set of choices for a beginner, but it has the potential to be modified well into the future, as new advances are made and ones tastes and diving styles change.

-the prism is a mix in philosopy between the simplicity of an mCCR and the conveneience of an eCCR. It combines a simple, independent po2 display with a traditional electronic set point controller. The distinguishing characteristic of the prism is that it comes with special o2 sensors. All o2 sensors are basically fuel cells, which generate electricity from the reaction they have with o2, this current is measured to extrapolated o2 concentration. The prism employs a special high output o2 sensor that produces enough electricity to power a mechanical needle style po2 guage…this back up display is designed to provide a comparison to the battery operated set point controller, if the primary fails, this display can be a lifeline and a trip saver, allowing for manual injection. It comes with front mounted counter lungs and a radial scrubber. The radial scrubber distributes exhaled breath from inside a column to outside rather than from one end of a cylinder to another…as with an axial scrubber. This tends to be much more efficient, boasting exceptional duration…which can equate into fewer pails of sorb needing to be hauled to remote locations.

-diverite’s Optima, boasts a tried and true set point controller, the hammer head electronics with two independent displays. For the most part, diverite has taken the approach of using already proven components, with the exception of the scrubber, which employs the state of the art micropore scrubber cartridge called the Extend Air Cartridge (EAC). An Co2 absorbent material that has been sprayed on a gortex like mesh and rolled into a cylindar. It’s users love it’s convenience and are willing to pay a premium for it. The optima is more modular than the inspo/evo in that it can take any standard harness, particularly, any one of diverites impressive array of tried and true harnesses that have enjoyed the many years of R&D that Diverite has put into their large OC gear market.

Hope that is a good start.

[mattwave]

Some good information George, but many details of your statements could be argued by the true experts (Who never post online). They are only painting a small picture of the true objectives behind each design, and they don't key in on any of the true advantages and shortcomings of each design.

edited once: to play nice

[CaptnJack]

Check out the RBW libraries. Very good writeups of virtually all the different units. You'll have to put the why/why nots together more for yourself though.

[Dmitchell]

-The KISS (the name taken from the military acronym Keep It Simple Stupid) is built with a philosophy of simplicity and independence in components. The KISS is responsible for popularizing the use of a constant flow orifice. It has 3 independent po2 only displays, one for each cell and each one is fully independent with it's own battery...no shared wires. It has back mounted, internal counter lungs (not ideal for bueyency or WOB, but reduces clutter to the chest). the KISS has non-pressure compensating first stages, which means it is depth limited in it's stock form, though this can be overcome with outboard o2 for the deep part of the dive. This can be the case for all non-depth compensating rigs. The reason for the non-depth compensating first stages is to help keep po2 relatively constant as pressure increases with depth.


Hope that is a good start.

Not bad! but since I'm a KISS diver I'll comment on that section.

First, the WOB is a little more but, I don't think it is all that much once you are comfortable with the unit. I'm not sure where you get the buoyancy thing. The CL's are CL's chest or back mounted. buoyancy is buoyancy and they are going to act the same. You will get chipmunk cheeks on the KISS if you roll over and look at the surface but again, it something you get used to. You'll also trigger the ADV in that position so I generally try not to lay on my back.

Second, the KISS has 1 non-compensating first stage on the O2 side. The Dil side is a standard 1st stage otherwise you couldn't operate the BC, ADV, Drysuit, BOV.



Dave

[Gill Envy]

hello there Matt,
If only the "true experts" would come out of the woodwork more often. The frustration I have found is that all too often the folks who promote themselves as the "true experts" don't post on line, not because they are above it all, but instead because they would rather have a captive audience in which to promote their own vested interests. I have my opinions and biase and nubile ignorance for sure, but I also have no commercial interests in the information I share. My hope is not to promote my perspective as the truth, but rather share yet another perspective.

Perhaps you'll like my edited version a little better, which will include helpful feedback and corrections I've gotten via PM. Perhaps you'd like to pass on some of your suggestions to be included? I'll be posting it probably on monday after all the relatives leave.

kind regards,
george

Some good information George, but many details of your statements could be argued by the true experts (Who never post online). They are only painting a small picture of the true objectives behind each design, and they don't key in on any of the true advantages and shortcomings of each design.

edited once: to play nice

[Curt McNamee]

Nice Post George !!!!. I felt that your post was very well done and was put in a very neutral format, especially after what you have been thru and experienced.

I know that people will benefit from your hard work by reading your post no matter what rebreather they end up purchasing. Knowledge is power.

It does seem to be interesting that some of the "so called experts" are the ones that steer people wrong when they do get involved just to benefit there own personal gains without regards for the entire picture.

You have very nicely put into words the best you can, a very detailed summary of the in's and out's of the different types of Closed Circuit Rebreathers. I know that you are working on a few corrections that you will be making to your write up.

Thanks for your contribution.

[mattwave]

[quote="Gill Envy"]hello there Matt,
My hope is not to promote my perspective as the truth, but rather share yet another perspective.


kind regards,
george
[quote]

The objective of my response was to challenge your expertise or lack of, a year plus and maybe 50 or so hours of CCR Diving shows in your thin, "Perspective". Why are you promoting it?

[Curt McNamee]

hello there Matt,
My hope is not to promote my perspective as the truth, but rather share yet another perspective.


kind regards,
george

The objective of my response was to challenge your expertise or lack of, a year plus and maybe 50 or so hours of CCR Diving shows in your thin, "Perspective". Why are you promoting it? Sounds shadey to me, more like a vendetta.

You should read Gill's first paragraph again. He clearly states what his level of experience is and welcomes input and corrections.

Instead of dogging him, why don't you contribute to this thread in a positive way by adding your comments and/or corrections like Dave Mitchell did.

All Gill is trying to do is help people with the very complicated information about rebreathers, which is more than alot of people are willing to do.

[mattwave]

Hey in mine any many other inspo diver's opinion out there, "YBOD" is fightn' words, the minute he used it in his perspective, it lost all credibility from where I am standing. Does that qualify as my input?

[Curt McNamee]

Hey in mine any many other inspo diver's opinion out there, "YBOD" is fightn' words, the minute he used it in his perspective, it lost all credibility from where I am standing. Does that qualify as my input?

YBOD is a very common acronym that has been in use way before you and I ever got involved in rebreathers, and as most people know it is a joke and a play on words which is not at all uncommon.

I know Gill's intent was not to ruffle anyones feathers over this seemingly sensitive issue that some people might have.

I am sure that with the help of your input, he can understand someone else's perspective and change the way he has worded information about the Inspiration CCR.

See now, was that so hard????.

[Solitude Diver]

...... If only the "true experts" would come out of the woodwork more often. The frustration I have found is that all too often the folks who promote themselves as the "true experts" don't post on line, not because they are above it all, but instead because they would rather have a captive audience in which to promote their own vested interests.

No..... I'd say the true experts ARE "above it all", and know it, and it is becasue they don't like to get sucked into these kind of "pissing matches". It is not because of self promoting, or they likely WOULD be here. I am not sure, but as I understand Matt is Peter Den Hann's son? Peter could certainly be considered one of the "True experts" (certainly THE expert for inspiration and evolution in the US). In anycase, I took one of Peter Den Hann's classes, he specifically suggested that we stay away from these forums just because of this type of BS. (OK, so maybe I didn't listen too well there).

All due respect to Matt and his background, if we relied on everyone posting on these to be "experts" there would be nothing but crickets. I think (in my humble opinion) everyone is entitled to their perspectives and opinions, and probably should be allowed that on this (supposed) friendly board. I joined assuming that a local board would have less of this than say ...some of the other boards.

[Solitude Diver]

BTW.... that was a nice post. A lot of time went into it, and regardless of the expertise, some research obviously went into it as well. It provides some good general information for newbies (like me).

I assume most people who are really trying to decide what to buy, would research more than just one thread prior to making a determination anyway, and there is not enough of these comparison type reports out there to narrow down (and expedite) the research process.

Thanks on behalf of us "newbies" for the time and effort.

[Gill Envy]

thanks for your words. since my post has stirred up some debate, i'm taking some time away from the relatives...not so hard actually, and cleaning up the post...and getting it vetted by a local instructor and a few others internationally...which is taking longer than i'd like, but the result should be more generally useful and appropriately qualified.

george

BTW.... that was a nice post. A lot of time went into it, and regardless of the expertise, some research obviously went into it as well. It provides some good general information for newbies (like me).

I assume most people who are really trying to decide what to buy, would research more than just one thread prior to making a determination anyway, and there is not enough of these comparison type reports out there to narrow down (and expedite) the research process.

Thanks on behalf of us "newbies" for the time and effort.

[mattwave]

How to compare and contrast the available rebreathers on the market is an eternal question and the answers are constantly evolving with changes in market trends. Few people really want to answer this question because few people own all the rigs. I am by no means a authority on the subject but I have owned two very different types and gotten some hours under my belt. I have put some time and energy into explaining the major differences as I have observed them. This list is not comprehensive, is not all first hand knowledge… but I thought it might be helpful to folks just starting on the path of gathering knowledge. My hope is that this list gets added to. Corrections are also welcome.

There are two main differences between available CCR's. there are those that require manual o2 addition (mCCR's) and those that rely on an electronic set point controller with a solenoid to monitor and inject o2 in the loop (eCCR's). Manual vs electronic only refers to the o2 injection as manual injection rebreathers are becoming more and more electronic with in-line deco, HUD's (heads up displays) and more integrated electronics, but continue to adhere, with near religious conviction, to leaving out the solenoid/ automatic set point controller. To ease the injection process a constant flow orifice or “leaky valve” is used to administer some o2 into the loop, requiring the diver to “top off” with manual injection to keep up with metabolism. It would seem that the trend in mCCR's is not so much in maintaining overall simplicity anymore but rather continuing to require the user to inject o2 manually and continuously monitor the effect of injection and metabolism on the loop’s po2.

Many of the firm believers in mCCR's have concluded that manual injection builds safer habits, as monitoring and adjusting loop o2 balance becomes deeply engrained in the diver, reducing the likelihood that a malfunction would go unnoticed. This conclusion seems to be supported by the near zero fatality rate associated with them, though the reasons for this low rate have yet to be determined. Many users simply like the fact that they have a better chance at finding a remedy for in field repairs since they are simpler, reducing the prospects of missing dives or whole dive trips.

The firm believers in eCCR's like the convenience of a set point controller, and often believe that it is a safety net in case of getting over task loaded or distracted. Eccr's seem particularly attractive to photographers and deep penetration wreck divers and cave divers, those for whom hands free function is a high priority. For reasons yet to be determined, there are many fatalities associated with eCCR's, which could reflect their added complexity, additional failure points, their tendency to tempt an "auto pilot mentality" or other factors yet to be determined (more people dive eCCR's, dive them more aggressively, possible need for changes in training standards, etc. etc.). the best attitude to take while diving any rebreather is that you are 100% responsible for what is happening.

The major contenders in the mCCR camp are the KISS, the Copis Meg, the rEVO and the Pelagian. the main features of destinction as I know them:

-The KISS (the name taken from the military acronym Keep It Simple Stupid) is built with a philosophy of simplicity and independence in components. The KISS is responsible for popularizing the use of a constant flow orifice. It has 3 independent po2 only displays, one for each cell and each one is fully independent with it's own battery...no shared wires. It has back mounted, internal counter lungs (not ideal for bueyency or WOB, but reduces clutter to the chest). the KISS has non-pressure compensating first stages, which means it is depth limited in it's stock form, though this can be overcome with outboard o2 for the deep part of the dive. This can be the case for all non-depth compensating rigs. The reason for the non-depth compensating first stages is to help keep po2 relatively constant as pressure increases with depth.


-the Copis Megalodon is identical to the standard eCCR version except for the electronics...front mounted counter lungs, solid build, very modular. The Copis head/electronics come stock with a KISS style constant flow orifice. It has several standard threaded ports which makes it very amenable to mixing and matching electronics from other manufacturers. The electronics that come stock are not fully independent, the displays share a case and the battery. In it’s stock form it is assumed that the diver is diving only to recreational depths with adequate bail out…additional redundancy is recommended to go beyond recreational limits. it has a non-depth compensating first stage, which means in it's stock form it is depth limited, again that depth limit can easily be overcome with off board o2 with a depth compensating reg to be plumbed in for the deep part of the dives.

-the rEVO has back mounted counter lungs, a unique electonics interface that is designed to reduce failure points. One of it's destinguishing characteristics is that it contains two scrubber sections, designed to reduce the chance of breakthrough. It has non-depth compensating first stages. There is also an eCCR version...the rEvo dream.

-the Pelagian has broken from the mCCR pack and offers a depth compensating first stage and an adjustible needle valve...allowing the diver to adjust, on the fly, the 02 flow to allow for changes in depth/pressure making it presumably appropriate for diving to practically any depth. it also has a unique front mounted counter lung design that boasts ideal trim. Many of it’s components are claimed to be readily available making service more convenient world wide.

-there are several electronics packages that are being offered by third party manufacturers that are often used to create added redundancy or replace the stock electronics altogether. The Shearwater, Hammer Head electronics, Universal Rebreather Monitor and VR3 are all third part electronics that are commonly used with eCCR's and mCCR's. Third party computers are often used with a 4th cell, for additional redundancy.

The rebreathers that I am familiar with in the eCCR camp are the Inspiration/Evolution with vision electronics, the Megalodon, The optima, and The Prism. One of the main distinctions among eCCR’s is weather they include truly independent handsets and weather they come stock with in line deco computers. The main features of distinction among brands as I know them:

-The Vision electronics are often referred to as the crem de la crem of eCCR's...the most complex and sophisticated of them all. They apparently dominate the current market. The main difference between the Evolution and Inspiration is size and duration. The inspiration and Evolution come with proprietary valves and a hard case, requiring brand name tanks and valves if used in the stock case, though there are third party frames that open up the options so that you don’t have to travel with the tanks. It comes with a temp stick to help confirm scrubber duration, a HUD (heads up display) and buzzer to help confirm proper set point controller function, onboard deco and a somewhat independent set of controllers. They require annual factory maintenance, and being more complex, it's usually back to the manufacturer for fixes as well. They can be costly to maintain but offer state of the art performance and impressive customer care. They have an apparent low mortality rate associated with them, at least the Vision version though it’s hard to determine mortality rate with any rebreather brand because all manufacturers unfortunately hold on tightly to total sold unit numbers and mortality figures. The original classic version is often referred to as the YBOD, or yellow Box of Death as many people perished while using them. One of the big suspected culprits of the classic was the excessive tolerances in the scrubber…allowing for co2 bypass.

-the Megaladon has front mounted counter lungs, a po2 set point controller, no on board deco. It boasts tank like build quality and devoted customer care, even assistance with in field repair. It comes with a HUD for po2 monitoring. Built to not require a cover, the meg is becoming legendary for it's modularity, allowing the diver to choose everything from the type of electronics to the type of wing, to the size and type of tanks and scrubber size and the list goes on and on...not an easy set of choices for a beginner, but it has the potential to be modified well into the future, as new advances are made and ones tastes and diving styles change.

-the prism is a mix in philosopy between the simplicity of an mCCR and the conveneience of an eCCR. It combines a simple, independent po2 display with a traditional electronic set point controller. The distinguishing characteristic of the prism is that it comes with special o2 sensors. All o2 sensors are basically fuel cells, which generate electricity from the reaction they have with o2, this current is measured to extrapolated o2 concentration. The prism employs a special high output o2 sensor that produces enough electricity to power a mechanical needle style po2 guage…this back up display is designed to provide a comparison to the battery operated set point controller, if the primary fails, this display can be a lifeline and a trip saver, allowing for manual injection. It comes with front mounted counter lungs and a radial scrubber. The radial scrubber distributes exhaled breath from inside a column to outside rather than from one end of a cylinder to another…as with an axial scrubber. This tends to be much more efficient, boasting exceptional duration…which can equate into fewer pails of sorb needing to be hauled to remote locations.

-diverite’s Optima, boasts a tried and true set point controller, the hammer head electronics with two independent displays. For the most part, diverite has taken the approach of using already proven components, with the exception of the scrubber, which employs the state of the art micropore scrubber cartridge called the Extend Air Cartridge (EAC). An Co2 absorbent material that has been sprayed on a gortex like mesh and rolled into a cylindar. It’s users love it’s convenience and are willing to pay a premium for it. The optima is more modular than the inspo/evo in that it can take any standard harness, particularly, any one of diverites impressive array of tried and true harnesses that have enjoyed the many years of R&D that Diverite has put into their large OC gear market.

Hope that is a good start.

First off all Productions CCR's on the market have the exact same objectives:
1. Scrub co2 from diver's exhaled breath - Radial or Axial Scrubber Design are the only design in full productions.
2. Replenish metabolized Oxygen - Automatically injected by a Solenoid or a Constant Flow Regulator - Most Production Rebreathers have manual add option as well (Sentinel does not). Primary objective maintain Constant PO2
3. Supply Diluent Gas via a manual add and/or demand valve.
4. Seal off or open loop via a direct surface valve (DSV)

They all have only two onboard bottles, one 100% Oxygen and one Diluent (Air to Trimix), a scrubber canister or two, a breathing loop and counterlungs.

Beyond these the features and design as well as configuration differ. The most available CCR on the market today are:
Meg (COPIS or APEKS)
KISS (Sport/Classic)
Evolution
Inspiration (Classic or Vision - class not available on Evo)
PRISM (Now manufactured by Hollis-Oceanic)
Ouroborous (Now also the Sentinel)
Cis Lunar (Redesigned and Manufactured by Poseidon)
Optima

Non Production CCR:
rEvo
Titan
Pelagian
MK15.5
There are many more in the prototype stage still.


There are more than just two differences in Production CCR Design.

eCCR: Electronically Controlled Oxygen Feed
Optima
Meg (Apeks)
Inspo (Classic or Vision)
Evolution
Sentinel
Cis Lunar

mCCR: Constant Flow Regulator
KISS (Classic and Sport)
Meg (Copis)

OTL: Over the Shoulder Counter Lung Design
Meg
Evolution
Inspiration
Optima
Prism
Cis Lunar

RMCL: Rear Mounted Counter Lung
KISS
Sentinel

Axial Scrubber:
Meg (Apeks and COPIS)
Evolution
Inspiration
KISS (Classic and Sport)

Radial Scrubber:
Meg (Aftermarket)
Cis Lunar
Sentinel
Prism
Optima (Extend Air Cartridges Only)

Objective #1:
Testing a CCR to pass a standard such as CE or ISO requires a high exertion rate by a test subject while unit successfully removes co2 to an except-able level (Most likely less than 300ppm). Only 3 production CCR have been tested and met this Requirement : Inspiration, Evolution and Ouroboros. These are the only CE certified CCR on the market although all production CCR's on the market are have not had issues with co2 breakthrough from design flaws. An expert (Tom Mount) once said that all the Rebreathers he certifies divers to use will effectively remove co2 if properly assembled and maintained. The debate between Axial and Radial designs returns to user preference, there is no solid fact either is inadequate or more practical, only personal preference and speculation. It is true that the media CCR uses to remove or scrub the co2 is highly reactive with salt water and can cause a caustic cocktail inflicting the diver with an extremely bitter and harsh taste, they must bailout. This has become a rare occurrence in CCR diving these days and it is much less likely to occur in the OTL design. The extend air cartridges used in the Optima boast they will not have a caustic reaction.

Objective #2
Replenishing metabolized oxygen is the sole purpose although maintaining a constant ppO2 (Nitrox 101 - Oxygen Pressure) is another primary objective. This gives the diver the best mix for every breath at any depth during the dive. This "Can" have advantages for extending No Deco Limits and minimizing inert gas loading and maximizing unloading. The difference in eCCR and mCCR was stated above but once not qualified completely.
mCCR: A constant flow of oxygen has it's limitations, the flow rate is set low enough so the diver's PO2 will not be too high at depth, but in the shallows with a high exertion rate or in an uncontrolled ascent; the PO2 in the loop can become dangerously low. The diver must manually add oxygen in such a situation. The blessing behind the design is that there is no battery or electronics supplying the Oxygen to the diver. As long as there is Oxygen in the bottle and the valve is turned on, the CCR is serving it's purpose. Another benefit is there is very little draw on the CCR's battery, they simply have a display with 3 values, stating each Cell's reading.
eCCR:Electronically controlled PO2 needs both a brain unit and a solenoid to achieve this objective, as well as a supply gas. They use a voting logic from 3 Cells, the two with the closest accuracy is considered the true PO2 in the loop and the brain unit tells the solenoid to inject as necessary. Two things here, all CCR uses Oxygen Cells (Sensors) to gauge the PO2 in the loop, most all have 3, the flaw in this voting logic design is that Cells are unstable by design and if 2 are equally unstable the brain could be using incorrect information to calculate how much O2 is needed. New 4 sensor designs and upgrades are the best option to rectify this flaw. Also the Vision electronics found in the Evo/Inspo boast the only AI (Artificial Intelligence) design, thus knowing exactly how much it takes to maintain the CCR's PO2. The Hammerhead found in the Optima, and the electronics in the Sentinel, Cis Lunar and Prism all boast intelligent injection, but the CE has approved both the Classic Electronics found in the Inspiration and the Vision Electronics in the Evo/Inspo to maintain a sliding set point durning an ascent >60fpm.
The early design of the Meg had a different brain that of today's Apeks models, it had intelligent injection and onboard deco, the designer was killed in a Helicopter Crash and his electronics have not been replicated. The current Apeks design works on an Interval Injection design and will inject only as it is set, example: 1/2 second of injection every 6 seconds. The solenoid also draws major power from the battery and since you have to solder the batteries together, most Apeks Meg divers manually assist the unit by adding O2 on their own. The original electronics had amazing power efficiency and an expert and good friend who still has these electronics says his battery can last all year. The new Apeks 3.0 boasts a progressive injection system, many devout users are eagerly awaiting it's arrival. The Optima has taken the injection a step further by injecting the O2 down a metal tube to the bottom of the scrubber canister allowing the loop gas to homogenize with the O2 before hitting the sensors, no substantial evidence supports flaws in the standard design.

Objective # 3:
All current models have an ADV (Automatic Diluent Valve) of one design or another that allows the CCR diver to add Diluent to offset Boyle's law diminishing the loop volume. Some designs offer a manual shut off so that once the diver has reached the target depth, they will no longer need to offset Boyle's law and will shut off the ADV not to fire it by turning upside down or taking in a deep breath. The Sentinel boasts a dil controller, but no reviews of this feature have been revealed.

Objective # 4:
All current models have a DSV (Direct Surface Valve) which will ensure no water will enter the CCR breathing loop when the diver has the mouthpiece out of their mouth. The KISS comes stock with a BOV (Bailout Valve), which allows the diver with a turn of a lever to immediately breath Open Circuit gas plumbed in via a hose from the Diluent Bottle or Bailout bottle slung to the divers side. There are aftermarket BOV's for most current models. Some divers complain of bulk out there in front of them, but many swear they will not dive without one.

Now the features, the Apeks Meg boasts an impressive HUD (Heads up Display) that blinks a certain interval using one of three colors to tell the diver exactly what each cell is reading for PO2. The Optima or Hammerhead electronics, has a HUD that blinks and vibrates to communicate with the diver. The Sentinel and Cis Lunar I have not used or sold or seen their huds, the Prism has a straight forward array of led lights that mean certain things, a little bulky by some standards. The Evo/Inspo with vision electronics boasts a very sophisticated HUD using 2 red and 2 green lights that can communicate several different warnings. The COPIS Meg and KISS do not come standard with HUDs but with the popular Shearwater electronics package upgrade you now have a HUD and an onboard deco computer.

As for warnings the Evo/Inspo and the Inspiration Classic are the only CCR's on the market with an Audio Buzzer fixed next to the divers head. The Sentinel, Cis Lunar, Optima, and the Apeks Meg all have warnings in either their HUD or Handsets or both. Warnings such as High or Low Oxygen, and Cell or Battery warnings. The Vision Electronics, Shearwater, Hammerhead, and Sentinel VR3 handsets have on board Deco Software and ascent, CNS, Deco, and OTU alarms. The KISS and COPIS Meg come with no alarms standard, but IMHO the serious warnings such as too Low or Too High PO2 should come after the diver has noticed them by closely monitoring their PO2. One of the features that the Vision Electronics posses is a Scrubber Warning, the Evo/Insp Vision scrubber canister is outfitted with a sophisticated temp stick with an array of sensors, scrubber media is reactive and warms when it's working. This gauge has been proven a very reliable method to calculating scrubber performance and duration. As stated earlier regarding the stability of Oxygen cells, the Evo/Insp Vision comes standard with PC download capability, giving the diver a thorough account of the last dives which can be an excellent tool gauging the performance of not only the scrubber but the O2 cells on the last dive. The Meg and the KISS are noted to be excellent for customizing and configuring with any reasonably sized cylinders backplate and wings, the Optima is criticized for hiding the cylinder valves making it very difficult to open and close during operation. The Evo/Insp and Prism have been criticized for not allowing a multitude of configurations such as the Meg or KISS. Alan Studley (Expert) claims a real benefit of the KISS is lack of clutter in the front as well as the placement of the buoyant scrubber canister allows easier trim for the KISS diver.

As for reliability, I have sold, operated and assisted in training of many units and each companny has had units needing to be returned to the factory for repair, both due to user error from, "Tinkering" and flat out unit failure.
They are complex to a degree and all manufacturers have stood behind their product 100%, once a diver was even given a Evo loaner while theirs was being repaired. The Meg displays a truck rolling over it on the website which is a testament for it's durability. The Vision electronics feature a black box which allows any information from the CCR to be recovered even after a major flood, although all CCR's risk major damage if flooded and not rinsed and dried immediately after flood.

Each of the 3 top Production Rebreathers Evo/Inspo, Meg and KISS I have overheard the acronym or catchy nickname given to the model with the word "Death" in place. I do not take diving deaths lightly and especially do not appreciate the CCR referred to as the cause of diver deaths.
CCR do not kill divers, divers kill divers, the CCR is an effective tool for the job. It is also an effective tool for achieving diving bliss, I encourage anyone interested in CCR diving to look within themselves more than any machine. A CCR diver needs to most of all not allow complacency and irresponsible decisions to cloud their judgement. Each CCR diver owes it to the community to dive their CCR within their limitations and not try to cheat the system.

[Solitude Diver]

Matt.....you've been busy!

Great job clarifying a few things (for me anyway).

[CaptnJack]

I did not know the CE objective was <300ppm CO2. That's ~25-30% less than atmospheric. Is there some rationale for this low value? I assume its because we only need a small amount of CO2 to trigger breathing and every hint of excess is badddd news at depth.

Richard

[mattwave]

I did not know the CE objective was <300ppm CO2. That's ~25-30% less than atmospheric. Is there some rationale for this low value? I assume its because we only need a small amount of CO2 to trigger breathing and every hint of excess is badddd news at depth.

Richard

Bingo, and besides the only way to ensure efficient results is to set a high standard, but the 300ppm is a general number, the variances in CE's expectations spans more than just one situational standard.

[scubagrunt]

"YBOD" is fightn' words,

Okay sorry I just can’t leave this one alone. Fighting words? Gezz, I’m confused here I have always been told that YBOD stands for “Your Best Option Diving” , I even have the T-shirt that Mike Fowler gave me saying so, how’s those fighting words?

[Gill Envy]

Matt, holly cow! There is some great stuff in there...so clean and clear and by far the most pluralistic and nuanced post i've ever read of yours! you went for it, nice contribution to the conversation!

I can certainly take it in stride that my attempt at simplifying a very complex subject was a bit too simplistic and ended up giving an uneven comparison and leaving some obvious stuff out and in need of some correction... I get that, it's in the works.

While I don't imagine you'll be completely relieved by my edits of my original post, I do hope it comes closer to achieving a valuable perspective...coming soon.

george

/quote]



First off all Productions CCR's on the market have the exact same objectives:
1. Scrub co2 from diver's exhaled breath - Radial or Axial Scrubber Design are the only design in full productions.
2. Replenish metabolized Oxygen - Automatically injected by a Solenoid or a Constant Flow Regulator - Most Production Rebreathers have manual add option as well (Sentinel does not). Primary objective maintain Constant PO2
3. Supply Diluent Gas via a manual add and/or demand valve.
4. Seal off or open loop via a direct surface valve (DSV)

They all have only two onboard bottles, one 100% Oxygen and one Diluent (Air to Trimix), a scrubber canister or two, a breathing loop and counterlungs.

Beyond these the features and design as well as configuration differ. The most available CCR on the market today are:
Meg (COPIS or APEKS)
KISS (Sport/Classic)
Evolution
Inspiration (Classic or Vision - class not available on Evo)
PRISM (Now manufactured by Hollis-Oceanic)
Ouroborous (Now also the Sentinel)
Cis Lunar (Redesigned and Manufactured by Poseidon)
Optima

Non Production CCR:
rEvo
Titan
Pelagian
MK15.5
There are many more in the prototype stage still.


There are more than just two differences in Production CCR Design.

eCCR: Electronically Controlled Oxygen Feed
Optima
Meg (Apeks)
Inspo (Classic or Vision)
Evolution
Sentinel
Cis Lunar

mCCR: Constant Flow Regulator
KISS (Classic and Sport)
Meg (Copis)

OTL: Over the Shoulder Counter Lung Design
Meg
Evolution
Inspiration
Optima
Prism
Cis Lunar

RMCL: Rear Mounted Counter Lung
KISS
Sentinel

Axial Scrubber:
Meg (Apeks and COPIS)
Evolution
Inspiration
KISS (Classic and Sport)

Radial Scrubber:
Meg (Aftermarket)
Cis Lunar
Sentinel
Prism
Optima (Extend Air Cartridges Only)

Objective #1:
Testing a CCR to pass a standard such as CE or ISO requires a high exertion rate by a test subject while unit successfully removes co2 to an except-able level (Most likely less than 300ppm). Only 3 production CCR have been tested and met this Requirement : Inspiration, Evolution and Ouroboros. These are the only CE certified CCR on the market although all production CCR's on the market are have not had issues with co2 breakthrough from design flaws. An expert (Tom Mount) once said that all the Rebreathers he certifies divers to use will effectively remove co2 if properly assembled and maintained. The debate between Axial and Radial designs returns to user preference, there is no solid fact either is inadequate or more practical, only personal preference and speculation. It is true that the media CCR uses to remove or scrub the co2 is highly reactive with salt water and can cause a caustic cocktail inflicting the diver with an extremely bitter and harsh taste, they must bailout. This has become a rare occurrence in CCR diving these days and it is much less likely to occur in the OTL design. The extend air cartridges used in the Optima boast they will not have a caustic reaction.

Objective #2
Replenishing metabolized oxygen is the sole purpose although maintaining a constant ppO2 (Nitrox 101 - Oxygen Pressure) is another primary objective. This gives the diver the best mix for every breath at any depth during the dive. This "Can" have advantages for extending No Deco Limits and minimizing inert gas loading and maximizing unloading. The difference in eCCR and mCCR was stated above but once not qualified completely.
mCCR: A constant flow of oxygen has it's limitations, the flow rate is set low enough so the diver's PO2 will not be too high at depth, but in the shallows with a high exertion rate or in an uncontrolled ascent; the PO2 in the loop can become dangerously low. The diver must manually add oxygen in such a situation. The blessing behind the design is that there is no battery or electronics supplying the Oxygen to the diver. As long as there is Oxygen in the bottle and the valve is turned on, the CCR is serving it's purpose. Another benefit is there is very little draw on the CCR's battery, they simply have a display with 3 values, stating each Cell's reading.
eCCR:Electronically controlled PO2 needs both a brain unit and a solenoid to achieve this objective, as well as a supply gas. They use a voting logic from 3 Cells, the two with the closest accuracy is considered the true PO2 in the loop and the brain unit tells the solenoid to inject as necessary. Two things here, all CCR uses Oxygen Cells (Sensors) to gauge the PO2 in the loop, most all have 3, the flaw in this voting logic design is that Cells are unstable by design and if 2 are equally unstable the brain could be using incorrect information to calculate how much O2 is needed. New 4 sensor designs and upgrades are the best option to rectify this flaw. Also the Vision electronics found in the Evo/Inspo boast the only AI (Artificial Intelligence) design, thus knowing exactly how much it takes to maintain the CCR's PO2. The Hammerhead found in the Optima, and the electronics in the Sentinel, Cis Lunar and Prism all boast intelligent injection, but the CE has approved both the Classic Electronics found in the Inspiration and the Vision Electronics in the Evo/Inspo to maintain a sliding set point durning an ascent >60fpm.
The early design of the Meg had a different brain that of today's Apeks models, it had intelligent injection and onboard deco, the designer was killed in a Helicopter Crash and his electronics have not been replicated. The current Apeks design works on an Interval Injection design and will inject only as it is set, example: 1/2 second of injection every 6 seconds. The solenoid also draws major power from the battery and since you have to solder the batteries together, most Apeks Meg divers manually assist the unit by adding O2 on their own. The original electronics had amazing power efficiency and an expert and good friend who still has these electronics says his battery can last all year. The new Apeks 3.0 boasts a progressive injection system, many devout users are eagerly awaiting it's arrival. The Optima has taken the injection a step further by injecting the O2 down a metal tube to the bottom of the scrubber canister allowing the loop gas to homogenize with the O2 before hitting the sensors, no substantial evidence supports flaws in the standard design.

Objective # 3:
All current models have an ADV (Automatic Diluent Valve) of one design or another that allows the CCR diver to add Diluent to offset Boyle's law diminishing the loop volume. Some designs offer a manual shut off so that once the diver has reached the target depth, they will no longer need to offset Boyle's law and will shut off the ADV not to fire it by turning upside down or taking in a deep breath. The Sentinel boasts a dil controller, but no reviews of this feature have been revealed.

Objective # 4:
All current models have a DSV (Direct Surface Valve) which will ensure no water will enter the CCR breathing loop when the diver has the mouthpiece out of their mouth. The KISS comes stock with a BOV (Bailout Valve), which allows the diver with a turn of a lever to immediately breath Open Circuit gas plumbed in via a hose from the Diluent Bottle or Bailout bottle slung to the divers side. There are aftermarket BOV's for most current models. Some divers complain of bulk out there in front of them, but many swear they will not dive without one.

Now the features, the Apeks Meg boasts an impressive HUD (Heads up Display) that blinks a certain interval using one of three colors to tell the diver exactly what each cell is reading for PO2. The Optima or Hammerhead electronics, has a HUD that blinks and vibrates to communicate with the diver. The Sentinel and Cis Lunar I have not used or sold or seen their huds, the Prism has a straight forward array of led lights that mean certain things, a little bulky by some standards. The Evo/Inspo with vision electronics boasts a very sophisticated HUD using 2 red and 2 green lights that can communicate several different warnings. The COPIS Meg and KISS do not come standard with HUDs but with the popular Shearwater electronics package upgrade you now have a HUD and an onboard deco computer.

As for warnings the Evo/Inspo and the Inspiration Classic are the only CCR's on the market with an Audio Buzzer fixed next to the divers head. The Sentinel, Cis Lunar, Optima, and the Apeks Meg all have warnings in either their HUD or Handsets or both. Warnings such as High or Low Oxygen, and Cell or Battery warnings. The Vision Electronics, Shearwater, Hammerhead, and Sentinel VR3 handsets have on board Deco Software and ascent, CNS, Deco, and OTU alarms. The KISS and COPIS Meg come with no alarms standard, but IMHO the serious warnings such as too Low or Too High PO2 should come after the diver has noticed them by closely monitoring their PO2. One of the features that the Vision Electronics posses is a Scrubber Warning, the Evo/Insp Vision scrubber canister is outfitted with a sophisticated temp stick with an array of sensors, scrubber media is reactive and warms when it's working. This gauge has been proven a very reliable method to calculating scrubber performance and duration. As stated earlier regarding the stability of Oxygen cells, the Evo/Insp Vision comes standard with PC download capability, giving the diver a thorough account of the last dives which can be an excellent tool gauging the performance of not only the scrubber but the O2 cells on the last dive. The Meg and the KISS are noted to be excellent for customizing and configuring with any reasonably sized cylinders backplate and wings, the Optima is criticized for hiding the cylinder valves making it very difficult to open and close during operation. The Evo/Insp and Prism have been criticized for not allowing a multitude of configurations such as the Meg or KISS. Alan Studley (Expert) claims a real benefit of the KISS is lack of clutter in the front as well as the placement of the buoyant scrubber canister allows easier trim for the KISS diver.

As for reliability, I have sold, operated and assisted in training of many units and each companny has had units needing to be returned to the factory for repair, both due to user error from, "Tinkering" and flat out unit failure.
They are complex to a degree and all manufacturers have stood behind their product 100%, once a diver was even given a Evo loaner while theirs was being repaired. The Meg displays a truck rolling over it on the website which is a testament for it's durability. The Vision electronics feature a black box which allows any information from the CCR to be recovered even after a major flood, although all CCR's risk major damage if flooded and not rinsed and dried immediately after flood.

Each of the 3 top Production Rebreathers Evo/Inspo, Meg and KISS I have overheard the acronym or catchy nickname given to the model with the word "Death" in place. I do not take diving deaths lightly and especially do not appreciate the CCR referred to as the cause of diver deaths.
CCR do not kill divers, divers kill divers, the CCR is an effective tool for the job. It is also an effective tool for achieving diving bliss, I encourage anyone interested in CCR diving to look within themselves more than any machine. A CCR diver needs to most of all not allow complacency and irresponsible decisions to cloud their judgement. Each CCR diver owes it to the community to dive their CCR within their limitations and not try to cheat the system.

[Gill Envy]

accidental double post...errased.

[mattwave]

Yah I figured I should put my money where my mouth is, but I should qualify that even with the valid information compiled from both posts, there is still more info to be told. Bottom line, is all walks of CCR divers are diving the 3 top units out there (Meg, KISS, Evo/Inspo) and we should appreciate us as a community. Most non CCR divers express concern and even ridicule fueled by lack of knowledge and/or ignorance. The incident and mortality rate was shockingly high in the late 90's and early 2000's, many believe not due to CCR design, but poor training. Today's training and especially in the PNW has a much higher universal standard. If anyone on this board is interested in CCR training, I believe this list is correct:

Leon Schammerhorn: Meg/Inspo/Evo up to Mixed Gas TDI/IANTD
Ron Akeson: Meg/Inspo/Evo up to Mixed Gas TDI/IANTD
Mel Clark: Meg/KISS/Inspo/Evo/Optiima to Mixed Gas TDI
Curt McNamee: KISS TDI
Peter Den Haan: Meg/Evo/Inspo/KISS/Optima/Prism to mixed gas NAUI-TEC/TDI/IANTD
Craig Williamson: Inspo/Evo/KISS TDI
Ron Micjim: KISS TDI
Matthew Den Haan: Inspo/Evo NAUI-TEC

Instructor Trainers:
Leon
Mel
Peter

Instructor Trainer to Mixed Gas Meg:
Leon

Instuctor Trainers to Mixed Gas KISS:
Peter Den Haan
Mel Clark

Instructor Trainers to Mixed Gas Inspo/Evo
Peter Den Haan


Again correct me if I am wrong.

[mattwave]

oops posted twice, daughter hit the track pad.

[Curt McNamee]

Great post Matt, thanks for contributing. Just one little correction, the rEvo is now a production rebreather.

Here is a chart that was created a while back by Jo Cribley with some good information on it for all to look at also.

http://www.freewebs.com/jocribley/Rebreather_word.doc

[Joshua Smith]

Good stuff in this thread! And thanks for playing nice, everyone. I'm brand new to the whole thing, but this seems like an exciting time to be diving this way- new CCRs in development, new electronics, and more people coming over to the "dark side" all the time!

I'm going stir crazy this weekend- my whole family came to stay with us for Thanksgiving, and Mrs. Nailer explained to me about how nobody really wanted to come down to the water and watch me get in it and disappear for an hour or more.....anyway, my "dive clearance" was revoked for the long weekend.

But I'll be in the water again next week!

[Pez7378]

Good stuff in this thread! And thanks for playing nice, everyone. I'm brand new to the whole thing, but this seems like an exciting time to be diving this way- new CCRs in development, new electronics, and more people coming over to the "dark side" all the time!

I'm going stir crazy this weekend- my whole family came to stay with us for Thanksgiving, and Mrs. Nailer explained to me about how nobody really wanted to come down to the water and watch me get in it and disappear for an hour or more.....anyway, my "dive clearance" was revoked for the long weekend.

But I'll be in the water again next week!

You poor, poor soul. Ask Joe what he did yesterday while I was diving at Sund Rock!

As far as the RB discussion, I am very thankful for this information. I am completely ignorant to the technology and although the idea of diving an RB intrigues me, because of my ignorance I dont trust the technology. When people talk to me about their RB and diving with them, my eyes glaze over. Not that I'm not interested, it's just too much information for my feeble mind to comprehend. So, please continue folks, because potential RB divers such as myself are paying close attention.....Right Joe?