Thinking of a rebreather

My personal opinion is that photographers and videographers should consider eCCR's as those divers tend to be more distracted during a dive than some other disciplines. A computer looking over your shoulder may buy you some time should you be momentarily distracted from monitoring your PO2, however it is a double edged sword. As was so rightly stated previously, complacency will kill and some people come to rely too heavily on the electronics.

It really boils down to your training, mindset and diligence, no matter which tool you eventually choose.

The one thing I would stress beyond all else is to choose a rebreather which has undergone rigorous 3rd party laboratory testing to verify manufacturers claims and overall functionality. The industry is starting to do this thank God. This is life support equipment but some of the units sold still rely on field testing, with some having only a small base of units manufactured. Unfortunately, it boils down to $$$$ needed for the testing, not willful negligence or profit taking above user safety. The testing is quite expensive, so it is nice to support those mfg's who have accepted the financial burden inherent in manufacturing life support equipment, gone this route and set a higher standard.

So I am thinking of getting a rebreather - either an SCR or an mCCR. Stupid bubbles. Fish no like bubbles. Me no like bubbles.

 

Anyhoo, my requirements:

1/ Modular and self-fixable/servicable

2/ Uses standard tanks

3/ Mainly for recreational depths

4/ Ability to use with my own backplate/wings (or any kind of BP/wings... no traditional BCDs)

 

The KISS Sport looks really good, especially for the price. Any other ideas or recommendations?

 

I was planning to take a trip down to the Red Sea later this year and get my training.

 

Vandit

I made the plunge and started diving the Sport KISS nearly a year ago. It's a great unit and I am very happy with it. Looking at your 4 requirements, I think you'll find that the KISS unit gets a Check on each point.

The group I dive with has been using rebreathers for many years, mostly the Dolphin SCR and the Inspiration / Evolution eCCR units. I did hundreds of dives both local and on trips and I was not at all tempted to shift to a rebreather. I witnessed too many hassles, breakdowns, missed dives, and technical glitches that could only be solved by a true expert. Last year I went on a trip where I was exposed to the Sport KISS unit and I was really impressed! It is a tight, small, serviceable unit with very few points of failure. It actually looked like fun to dive it.

My dive shop (Silent World near Seattle) started carrying KISS after years of mostly pushing the Inspo / Evo and I started doing my research. This is probably the top Rebreather shop in WA, and the owner really knows all of the units AND the people who sell them. Based on what I saw and his recommendation, I bought a Sport KISS and took the training.

My impressions:

• Simple unit, easy to service.

• After about 20 dives, I can put the striped down unit together in 20-30 minutes.

• Nightly service cycle on a multi-day trip takes about 15 minutes.

• No mechanical problems so far. The only electronics are the PO2 readouts.

• Manual CCR is safe and simple. An electronics failure won’t take your trip.

• I've missed 1 dive out of about 50 on the unit, due to an error on my part and being cautious.

• No complaints about work of breathing. Others may be better but this one is great.

• I love setting up the unit and then doing 3-4 dives without touching it again.

• Finally, I don’t scare the fish away and I get fantastic bottom times.

Definately check out several units, and make sure you a comfortable with the mechanical & maintainance tasks that CCR ownership entails. The KISS is pretty low maintainence but it's more than Scuba. And of course a CCR can kill you if used improperly...

Dave

My personal opinion is that photographers and videographers should consider eCCR's as those divers tend to be more distracted during a dive than some other disciplines. A computer looking over your shoulder may buy you some time should you be momentarily distracted from monitoring your PO2, however it is a double edged sword. As was so rightly stated previously, complacency will kill and some people come to rely too heavily on the electronics.

If the diver can't exercise the disipline to monitor their intruments, then they should not be diving a CCR at all. (And probablly not Scuba either!) One on the KEY safety benefits to mCCR is that you do have to monitor and adjust your mix yourself. It's like I used to treat the Table Saw in shop class. If you don't have a health respect for the blade, it WILL bite you!

I also am totally up for having this thread hijacked. I would like to start rebreather diving at some point, and have to make decisions between mCCR, eCCR, hybrid, blah blah blah.

For some reason, the units that come to mind are the Evolution, rEVO and KISS. I know that Ryan moved from the KISS to the rEVO, and I'm dying to know why. It could influence my decision a great deal!

The $1k rebreather is another option if it is out by the time I am ready to buy. Am also going to starting haunting the rebreather forum.

The deep life rebreather has been talked about for years, but it still is vapourware.

For some reason, the units that come to mind are the Evolution, rEVO and KISS. I know that Ryan moved from the KISS to the rEVO, and I'm dying to know why. It could influence my decision a great deal!

The Evolution is a great rebreather, but it is sometimes difficult to get hold of the small tanks in remote locations. You can fix this by buying a travelframe from Decoweenie, then you can mount any size tank. The profile in the water is also a bit bigger because of the OTS (over the shoulder) lungs. And if the electronics go, you could miss a dive or even a trip. The latter never happened so far. If you are interested in deep diving; the Evo is certified to 150 meters.

With the rEvo you have BMCL (back mounted counter lungs). This keeps your chest free and reduces the profile. The rEvo has probably one of the smallest profiles due to the dual scrubber setup. If the electronics go, you just use it as an mCCR. It has been taken down to 150 meters recently on a wreck dive in Egypt but I'm not sure what depth the rEvo is certified for.

I have no personal experience about the KISS so I'm not going to comment on that unit.

With the rEvo you have BMCL (back mounted counter lungs). This keeps your chest free and reduces the profile. The rEvo has probably one of the smallest profiles due to the dual scrubber setup. If the electronics go, you just use it as an mCCR. It has been taken down to 150 meters recently on a wreck dive in Egypt but I'm not sure what depth the rEvo is certified for.

hi all,

for the eCCR version we did not yet advise a max depth, but that will probably be linked to what WOB you will allow, and what temperature you will dive:

in the near future we will release different WOB options, or kits that can be added to the standard rEvo.

with the lowest WOB option, and using the dual radial scrubbers, I suppose 160m is no problem in +10° celcius water.

paul

hi all,

for the eCCR version we did not yet advise a max depth, but that will probably be linked to what WOB you will allow, and what temperature you will dive:

 

in the near future we will release different WOB options, or kits that can be added to the standard rEvo.

 

with the lowest WOB option, and using the dual radial scrubbers, I suppose 160m is no problem in +10° celcius water.

 

paul

Hi Paul,

thanks for participating in this thread.

I have a question. I find WOB one of the most important aspects on a rebreather because it can and has caused CO2 retention problems. Can you give us an idea how the WOB of the rEvo compares to the WOB on the KISS and the Evolution/Inspiration?

Also is there a big benefit from the radial scrubbers compared to the axial scrubbers?

Peter

As Matthew pointed out with eCCR’s and divers that are more prone to be distracted during a dive, relying on a computer flying the system for you may buy you some time should you be momentarily distracted from monitoring your PO2, but it should never be a replacement for the central processor between your ears. To me, running a electronic set point for PO2 is the same as putting your car in cruise control. Just because its on doesn’t mean you shouldn’t be watching both the dash and road while you are driving.

It’s that type of complacency - rely too heavily on the electronics that has gotten people killed on eCCR’s. What it boils down to is your training, mindset and above all diligence.

Taking it from Tom Mount, master rebreather instructor and former underwater photographer back in the 70’s and early 80’s has this to say about CCR’s "For the diligent diver, closed circuit rebreathers are actually safer than open circuit scuba."

Now when it comes to choices between eCCR’s and mCCR’s, I am little bias towards mCCR’s. My own evolution with rebreathers began, like many with the Drager Dolphin SCR back in 2001. In 2003 I wanted to go fully closed so I got trained and certified on the Inspiration Classic. For the next year, and 25 hours (you log your underwater hours like a pilot logs their flight time) later, as wonderful as it was to be totally silent, not to mention having more time to do what ever underwater, the electronics in that system reaffirmed by belief about electronics in the marine environment. As any here knows electrical systems are deathly allergic to saltwater. To say the least I had a few dives aborted, missed or near missed from fussing with the unit during setup to just having something in wiring go south requiring me to either bailout or resort to flying it manual.

Eric, I don’t know fully why Ryan switched from the KISS Sport to the Pelagian to a eRVO, but you are welcomed to call me for more info on the various systems.

As for the KISS Sport, I will say this. Since picking up one year ago I have been very pleased with it. Not missed a single dive (more than 100 hours on it now) do to something going wrong with the unit, nor have I found it difficult to use. On the contrary, compared the Inspiration it has been a joy for same reasons as cited by Dave Hicks.

1. They are easy set up (20 minutes tops), and break down and clean.

2. Simple unit, easy to service. ith the exception of the units two regulator first stages, you can pretty strip down and repair/replace anything on it with a small Phillips and standard flat screwdriver, cresitwrench, and needle nose pliers. One leatherman in the toolbox and you’re ¾ there.

3. Being predominately mechanical, with the only electronics being three independent PO2 readouts, problems have been almost non-existent so far. Manual CCR’s have the best track record for safety in CCR’s. I particularly love the fact that once it set up, I rarely need to touch or fuss with the unit between dives.

4. WOB - I have experience with both backmounted and over the shoulder (OTS) counter lung models to make some comparisons. Yes OTS are somewhat better for WOB, but they also ad clutter to your neck and chest, where as back mount does not. Everything is a compromise.

5. For travel, if you don’t need to bring the tanks, the entire unit can be compressed down to fit easily in carrying on.

6. Cylinder requirements (for air and O2) - pair of 13’s, 14’s, 17’s or 19’s, steel or aluminum.

7. Sorb – The Sport KISS can use just about anything out there from the stuff used in Drager Dolphins to the finer mesh required for the Inspirations and evolutions.

8. Onboard electonics – only three, basic PO2 monitors. To dive it in a recreational capacity (10 to 130 feet) and any two gas programmable nitrox computer will do.

9. And finally, in addition to the fish being a little more cooperative, you have time. Last summer me Doug Ebersole pulled an 84-minute dive with sandtigers (see photo below) in 90 feet of water with no deco obligations, other than a three minute safety stop, at the end.

In addition to myself, Doug Ebersole, and Dave Hicks on this thread. Here are a few more photographer/videographers currently dive KISS rebreathers.

Alan Studly

Mar Shargel – who just published the California book Wonders of the Sea.

Berkly White – owner of Backscatter.

Norbert Wu – I think most everyone knows who Norb is.

If you are still in the tire kicking phase of your decision on going CCR, it really helps to go back those three back issues of the Underwater Journal. Me Doug have put a lot of work into this subject with still more to come.

And should you do, welcome to the Dark Side.

As Matthew pointed out with eCCR’s and divers that are more prone to be distracted during a dive, relying on a computer flying the system for you may buy you some time should you be momentarily distracted from monitoring your PO2, but it should never be a replacement for the central processor between your ears. To me, running a electronic set point for PO2 is the same as putting your car in cruise control. Just because its on doesn’t mean you shouldn’t be watching both the dash and road while you are driving.

Walt,

Heads up displays (HUDs) make diving an ECCR easier and safer. I wouldn't dive one without. With the HUD wou don't need to have your eyes glued to your handsets all the time like you had to do on your Inspiration Classic. The HUD sits in your vision. And you have also your ears. You can hear the solenoid firing what gives a good indication that your computer is working.

At the important waypoints during the dive like jumping in, changing setpoint, reaching the bottom, .. I use my handsets. Most of the time I rely on my ears and the HUD.

The big benefit for me as videographer is that I can keep my hands on my camera all the time. I don't have to push a button every X-minutes/seconds. There are shots that are difficult if not impossible to make on an mCCR. As an example ascending and filming at the same time. You need three hands to do that .

There are some people that dive an eCCR (without leaky valve) but control the setpoint manually. That is something that I really don't understand. If you want an mCCR, buy an mCCR or a hybrid like the rEvo.

Take care,

Peter

Hi Paul,

 

thanks for participating in this thread.

I have a question. I find WOB one of the most important aspects on a rebreather because it can and has caused CO2 retention problems. Can you give us an idea how the WOB of the rEvo compares to the WOB on the KISS and the Evolution/Inspiration?

 

Also is there a big benefit from the radial scrubbers compared to the axial scrubbers?

 

Peter

Peter, depending what WOB you want, because you can choose.. (the smaller the unit, small hoses, small mouthpiece (less dragg), using big grain sorb in stead of small grain in warm water etc etc)

next week I'm again at ANSTI to test 4 different new low WOB kits, and our new dual radial (yes radial makes a hell of a difference when using small grain sorb)

will publish the results then, but it is clear that the rEvo outperforms both (w're aiming below 2 j/liter at CE testing standards...)

paul

Agreed, HUDs (heads up display) make monitoring your PO2 easier and possibly safer, particularly in situations where your hands are full, or as cave divers have pointed out, when the environment has gotten so dark and silty that you can’t read your hand sets. But HUD’s are not exclusive to only eCCR’s. They are also adapted to mCCR’s. Both Shearwater and Subsea Systems provide the hardware to do it to both eRVO’s and KISS.

Peter, I am sure you remember all those drills you had to perform during your rebreather training – dil flushes, open circuit bailout, flying your system manually, etc., are there for a reason. That your system’s controlling electronics are not infallible. They can at any time, and they all do – saying this from personal experience, go wrong on you, by either taking a time out (CPU crash) or telling you everything is still all right when its not.

KISS rebreathers are not fancy, but they do work with the least amount of problems, and almost ZERO fatalities. eRVO’s, I seen the system, could no find anything that I didn’t like about system. And yes, in addition to manual, it also comes in hybrid version, which many are in the opinion (me included), offers the best of both worlds.

As for WOB, as Paul has outlined above, there are a lot of factors that influence breathing resistance on a rebreather. Outside of what can be measured mechanically in gas flow resistance tests, the rest is mostly subjective in nature as delivered by the person(s) actually wearing/testing the unit in the water. There again influencing factors that come into play include how hydrodynamic drag that that person has on them, work load, water temp, to the individual’s physical fitness.

If the diver can't exercise the disipline to monitor their intruments, then they should not be diving a CCR at all. (And probablly not Scuba either!) One on the KEY safety benefits to mCCR is that you do have to monitor and adjust your mix yourself. It's like I used to treat the Table Saw in shop class. If you don't have a health respect for the blade, it WILL bite you!

Dave. You must have missed the words "momentarily distracted" in my post. Which reminds me that a rebreather diver should also have the ability to pay close attention to detail, from setup to post-dive regardless of mechanical or electronic control . Too many near misses can be directly attributed to lackadaisical adherence to details & procedures.

I am surprised no one has talked about the other, and equally important part of my post... the need for third party published verification of safety and performance. Rebreathers in any other field, such as mine rescue, firefighting, etc., must be tested and certified to a minimum standard. Not so in diving... so buyer beware.

Here is a clip regarding work of breathing, counterlung design and placement which may be helpful to readers. It was originally posted in the Prism II section of Scubaboard by the Hollis group. It is probably one of the clearest explanations of fairly complex principals.

"The new method of counterlung evaluation that Dr. Dan Warkander (US Navy NEDU) presented at the DAN tech conference in Raleigh deals with 3 breathing factors that must be evaluated for closed circuit systems. Resistive effort is one; this is the difficulty of pushing or pulling gas in the breathing loop, the difference between a soda straw and a snorkel. Hydrostatic Loading is another; this is the relative difference between the pressure center of the diver’s lungs and the maximum and minimum pressure differentials when the counterlung is fully inflated and fully emptied. The last is Elastance; this refers to the change in shape of the counterlung as its volume changes during a breath.

Each of these 3 elements causes the diver to do work when breathing. You can have a mix of theses 3 kinds of work but at some point the diver will become fatigued just from the work needed to breathe. Lower work of breathing is a design objective.

In a normal swimming position the hydrostatic load of back mounted counterlungs produces negative lung loading, and chest mounted counterlungs produces positive lung loading. The hydrostatic load of over the shoulder counterlungs comes very close to reducing lung loading to zero. Less lung loading is less work to breathe.

Small diameter air passages have higher resistance to flow, or resistive effort. So do elbows, long tubes, flow direction mushroom valves, and thick scrubber beds. Using a sufficiently large diameter throughout the breathing loop, avoiding bends and elbows, using low durometer mushroom valves, and a radial scrubber all reduce resistive effort. Lower resistive effort is less work to breathe.

Elastance is related to hydrostatic load changes during breathing. A large flat counterlung (flat side down) would have lower elastance than a long narrow tube (tube vertical in the water column). Over the shoulder counterlungs seem to be a good shape tradeoff for low elastance. Lower elastance is less work to breathe."

The debate over the benefits and safety considerations when selecting either mccr or eccr has been ongoing within the forums of Rebreather World and Scubaboard for quite some time now. Within each of the different threads pertaining to this subject, I've read valid points on each side of the discussion, which leads me to the opinion that being able to run your unit either manually or electronically, depending on the particular situation a diver is faced with at any particular point in time, is probably the right solution.

Personally, I run my Optima electronically, but there are situations during a dive where I feel as though running my unit manually is beneficial. For example, yesterday, during the decompression hang on the third dive of an all day three dive trip, my handset signaled that my battery power was not as high as I would of liked it to be. Consequently, even though I had plenty of battery power to finish that dive and then some, and I have backup alternatives to deal with a battery failure, were that to have happenned, I opted to instead drop my setpoint well below the point I was flying it at during my decompression, and maintain my PO2 manually, which aided in conserving my battery power and ensured that my battery never got to a point where it might have affected my handset. That's just one example of many, but the bottom line is that it's good to have the option to switch between either mccr or eccr.

Therefore, I'd have to side with the eccr side of the debate, because unlike mccr's, eccr's give you the flexibility of switching between mccr or eccr, at any given moment, either before, during or after the diver.

Adrian

Peter, depending what WOB you want, because you can choose.. (the smaller the unit, small hoses, small mouthpiece (less dragg), using big grain sorb in stead of small grain in warm water etc etc)

 

next week I'm again at ANSTI to test 4 different new low WOB kits, and our new dual radial (yes radial makes a hell of a difference when using small grain sorb)

 

will publish the results then, but it is clear that the rEvo outperforms both (w're aiming below 2 j/liter at CE testing standards...)

 

paul

just as extra info:

rEvo rebreathers announces:

Because of the excellent cooperation with Shearwater Research Inc, and the belief and confidence in their products, rEvo rebreathers will start supplying their rebreathers with a wide range of Shearwater electronics.

Besides the current mCCR rEvo with dual rEvodream and HUD's (package 1), the newly available electronic packages on the basic rEvo rebreather will be:

Package 2: hardwired triple PPO2 display with depth/time function combined with one rEvodream/HUD

(can be upgraded to package 4 and package 6)

Package 3: triple PPO2 display with depth/time function with fisher connector combined with one rEvodream/HUD

(can be upgraded to package 5, but not to set-point controller)

Package 4: hardwired full trimix OC/CC computer with real-time PPO2 tracking combined with one rEvodream/HUD

(can be upgraded to package 6)

Package 5: full trimix OC/CC computer with real-time PPO2 tracking with fisher connector combined with one rEvodream/HUD

(no upgrade to set-point controller possible)

Package 6: set-point controller for complete e/hCCR function, with full trimix OC/CC computer with real-time PPO2 tracking combined with one rEvodream/HUD

To each package an extra rEvodream/HUD can be added, for triple electronic redundancy.

rEvo rebreathers believes that this new range of electronic packages allows the user to compose their rebreather the way he prefers, at the least cost.

Paul Raymaekers

ps: more about new WOB upgrades will follow end of the week

Great discussion and some very useful info, thanks all!

I have a few more questions, which hopefully will help others in the same boat as we me:

1/ Walt, you wrote:

" To dive it in a recreational capacity (10 to 130 feet) and any two gas programmable nitrox computer will do. "

Does this mean that the KISS provides a fixed fO2, as opposed to a fixed PPO2?

2/ Matthew, you wrote:

"Each of these 3 elements causes the diver to do work when breathing..<snip>.. but at some point the diver will become fatigued just from the work needed to breathe. Lower work of breathing is a design objective."

Now, is CO2 buildup due to WOB a real issue with most rebreathers, or a theoretical risk to be avoided?

3/ Peter, you wrote:

"There are shots that are difficult if not impossible to make on an mCCR. As an example ascending and filming at the same time. You need three hands to do that"

Ok, now I am a little confused. I was under the impression that even with mCCRs using fixed mass systems, you didn't have to actually adjust the dliuent/O2 every time you changed depth.. only if there was a significant change in breathing rate. I can often see myself moving up and down a significant bit (eg, when trying to photograph barracudas in mid-water) while taking photos. If I need to be fiddling with the O2 mix every time I go up and down, then yeah, perhaps eCCRs may be the way to go.

4/ Paul, we've been on email discussing the rEVO as well. I've sent you a separate email with a few questions as well.

Walt, I am on the islands on a hamster-powered internet. Downloading a 6MB file is about as likely as Angeline Jolie coming to give me a full body (her's) massage. I'll be downloading those issues when I have access to a faster connection starting a week or so from today.

I am indeed converting to the Dark Side - plan is Nov to the Red Sea to get certed. The only question is, what sort of scubasaber will I carry

Cheers,

Vandit

Now, is CO2 buildup due to WOB a real issue with most rebreathers, or a theoretical risk to be avoided?

A high WOB WILL cause CO2 retention. This is a real danger, not a theorethical one. Combine any rebreather with excercise, like swimming with a camera against a current and you risk CO2 retention. Any rebreather breathes more difficult than a normal regulator.

I had two issues with CO2 retention. The first one caused me to bailout at 50 meters with a good half hour of deco. That one was no fun at all. And my RMV was through the roof for a couple of minutes. The second one happened a year ago when finning against the current at 60 meters with a large video housing. I managed to stay on the loop that time, but it came close. So I take CO2 retention very seriously.

3/ Peter, you wrote:

"There are shots that are difficult if not impossible to make on an mCCR. As an example ascending and filming at the same time. You need three hands to do that"

 

Ok, now I am a little confused. I was under the impression that even with mCCRs using fixed mass systems, you didn't have to actually adjust the dliuent/O2 every time you changed depth.. only if there was a significant change in breathing rate. I can often see myself moving up and down a significant bit (eg, when trying to photograph barracudas in mid-water) while taking photos. If I need to be fiddling with the O2 mix every time I go up and down, then yeah, perhaps eCCRs may be the way to go.

An MCCR injects O2 slightly below you O2 metabolism rate. So if you stay a the same depth you have to press the manual o2 injection button every x minutes. If you rise in the water column the volume of the counter lungs will expand. This cuases a PPO2 drop, so you will have to add O2 manually to compensate. You will also have to vent the extra volume to keep the loop at minimal loop volume, but that can easily be done via the nose or by loosening the grip of your lips on the mouth piece.

There used to be a valve for the KISS that allowed the diver to add O2 with his tong, but that is not available any more.

2/ Matthew, you wrote:

"Each of these 3 elements causes the diver to do work when breathing..<snip>.. but at some point the diver will become fatigued just from the work needed to breathe. Lower work of breathing is a design objective."

 

Now, is CO2 buildup due to WOB a real issue with most rebreathers, or a theoretical risk to be avoided?

 

 

Cheers,

Vandit

Hello Vandit.

Co2 buildup/ breakthrough is one of the most critical issues in rebreather diving today. It can and does affect all rebreathers, regardless of design. There are ways to minimize the potential for critical buildup, which should be covered in any RB class.

There is no direct measurement of CO2 concentrations being done in any "sport" rebreather on the market today and this ability to measure CO2 in the breathing loop could be considered the holy grail of safe rebreather design (along with accurate gas delivery and control). Several ideas are floating out there of how to do such measurements accurately, and some industrial applications already do such measurements. Now we just have to find a way to make these measurements in the humid environment of the breathing loop in a consistent, cost effective way that does not require complex maintenance to assure accuracy.

There are thermistors (temp sensors) on the market which can to some degree measure CO2 scrubbing activity but I have not yet seen any peer reviewed, credible source white papers which show with certainty that they are an accurate gauge. They must not be confused with measuring CO2 concentrations inside the loop at any given point in time. They do not.

Work of breathing has direct and indirect effects on CO2 buildup and can be minimized through rigorous design and testing.

Again, independent testing is the #1 benchmark I would use at this time when deciding on which rebreather to purchase. One of the most deplorable issues in this market today is that known, critical design flaws which come to light are not immediately broadcast to the RB manufacturers customer base, and several designs presently on the market have known, critical design flaws yet are still being marketed as is.

Remember, they are simply tools, not an extension of your ego, so don't get caught up in the "mine is better than yours" debates. Choose the tool which has independent laboratory testing behind it and a company which is responsive to, and protects their customer base.

Design flaws can and do happen in any industry but not alerting your customers when they become known is inexcusable.

Automotive hard & soft recalls come to mind here.

I have dived many different rebreathers - all while using a camera - and whilst the WOB on paper may be vastly different, I have never found it to be an issue underwater.

The best solution to CO2 build-up is to start any high work or deep dive on a clean scrubber, and to get out of the habit (that all us photographers have) of holding our breath while taking a picture.

eCCR are fine on deep dives, but can be a hassle when working on fine positioning for macro pics on shallow dives. A slight rise can lead to a runaway O2 injection and runaway buoyancy. If you have to resort to flying an eCCR manually in such situations, mCCR is a much smoother solution. Inspiration/Evolution rebreathers are particularly aggressive on O2 injection for this type of work.

My latest toy is a rEvo with the hybrid mCCR/eCCR and I confess it is the nicest rebreather I have ever dived and extremely well engineered. I can shift between manual and electronic control as suits the job. My only caution is that whilst it is very light out of the water, it is also very negative in the water. Fine with a thick wetsuit or drysuit, but it could be an issue if I tried to dive it wearing anything less than 5mm of neoprene. My second choice would be a Megalodon, which I understand is now also available in hybrid mCCR/eCCR form.

Get an integrated dive computer and maintaining a stable PO2 for those ascending chase shots is not an issue, just let it wander and let the computer work out the deco, though as a diver you still have to make sure the PO2 does not drop below danger levels. An eCCR in such situations can again lead to runaway O2 injection while chasing the set point.

John

My latest toy is a rEvo with the hybrid mCCR/eCCR and I confess it is the nicest rebreather I have ever dived and extremely well engineered. I can shift between manual and electronic control as suits the job. My only caution is that whilst it is very light out of the water, it is also very negative in the water.

John,

how is your trim with the rEvo. Do you need extra weights at the top?

Peter