• Welcome to ScubaBoard

  1. Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

    Benefits of registering include

    • Ability to post and comment on topics and discussions.
    • A Free photo gallery to share your dive photos with the world.
    • You can make this box go away

    Joining is quick and easy. Login or Register now by clicking on the button

If you have any questions

Discussion in 'Rebreather Diving' started by King_Neptune, Jul 21, 2000.

  1. padiscubapro

    padiscubapro Cave Instructor

    # of Dives: I'm a Fish!
    Location: New York
    There are 2 main types of rebrerathers SCR and CCR with SCR having a few sub types. The SCR is the easiest to use and will give you about a 5x efficiency over open ckt.. Your mix must be chosen based on max depth and has limitations like those of standard nitrox.. For the most part they are not inherently any more dangerous, The danger come in mostly when trying to perform deeper dives..
    A CCR requires more training but has many more benefits, the main being you are always breathing the optimim gas and leave no bubbles. The effiency can be on the order of 100 to one over open ckt. They are a bit more complex and require monitoring but a properly trained and experienced CCR diver is probably safer than open ckt, however a poorly trained and careless diver can probably make themselves a statistic easier than with OC there are additional ways to hurt oneself... Personally I don't dive OC anymore unless I absolutely have to, All my dives nowadays are on a CCR. I've gotten spoiled by being able to easily do 3 hours dives with at least half of that deeper than 100 and with the proper multilevel planning no deco afterwards..
    There is lots of articles on the net about rebreathers, here is a link to get you started by Richard Pyle.


    Dive safe...
    Tec and Rec Scuba instruction, including INSPIRATION CCR
  2. DrySuitDave

    DrySuitDave Contributor


    How do you like your Inspiration? I have my sights set on one. I have dived OC for 20 years....I always dive by myself as I have complete confidence, and aside from a few stupid people I got stuck with buddy'ing up with with that ran out of air and yanked my first stage and never gave it back, I have handle the infrequent few equipment malfunctions at depth with aplomb.

    But how is it diving by ones self on CCR? Ok, so you have to monitor your PPO2, adding/venting upon ascending/descending, diluent flushing, blah blah all associated with competent training etc....so what is the scoop? Feel confident in diving alone? Ever run into a problem with your rig? Ever have one of your sensors malfunction or read different than the other since the Inspiration controls use voting logic?

    How do you time your sofnolime duration time?

    I have read lots of stuff on people dying on Inspirations, but they are the second most widely used rebreather and unlike the more used Draegers, they are used far deeper. Many deaths seem health related though such as heart attacks, etc, all of which can occur doing OC.
  3. padiscubapro

    padiscubapro Cave Instructor

    # of Dives: I'm a Fish!
    Location: New York
    I'm an inspiration instructor (there aren't many of us in the USA). You have lots of good questions, but some I'd rather not answer in an archived public forum(there are 2 answers to many questions.. the official answer and the what most experienced CCR divers actually do). send me an email with your phone # and we can chat at length.. I'll give you an honest assessment of the unit and its pluses and drawbacks..you can email me at padiscubapro@yahoo.com, my contact info is also listed on the ambientpressurediving web site..

    Joe R
  4. WetDane

    WetDane Contributor

    Has anyone taken a closer look at the new RB80 breather?


    Big T
  5. roakey

    roakey Old, not bold diver ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: Colorado Springs, CO
    Do you know Claudia Milz? (http://www.orcatechdiving.com/)

  6. WetDane

    WetDane Contributor

    Only from what I read on Quest - I have met her once I think, with Garrett last summer... that's it...
  7. mike_s

    mike_s Solo Diver


    so are these still the wave of the future? (anyone)
  8. berk

    berk Instructor, Scuba

    # of Dives:
    Location: Philly
    For deep diving and helium, they're the balls, and already taking over many seats on deeper charters. I'm not a cave guy so I wouldn't know there.

    I say no way for shallow diving. I think diving them with air diluent is a bad idea as it is past 80-100' for "work of breathing" issues. I think they're more dangerous than made out to be, but that's just my opinion and I'm a douche.

    If you have real questions I'd ask PADIPRO, the guy upstream in the thread. If he's the right "Joe R," he's without a question one of the most knowledgeable guys out there: from writing manuals for agencies on down to crazy balls minutia of the electronics and testing them out. Real world street wise info stuff too like not putting thermo valves on your oxygen side since they suck when it comes to feathering etc.

  9. battles2a5

    battles2a5 Divemaster

    # of Dives: 200 - 499
    Location: Charlotte, North Carolina
    That's the big question that nobody wants to address when they start talking about recreational rebreathers. OC rec diving has inherent risks, but it is more or less a safe activity. Technical diving (deep, mixed gas, hard and soft overhead) is an inherently dangerous activity that can be done with relative safety. Doing these dives on OC has more static risks that are hard to mitigate fully (e.g. loss of gas, having to switch gases, etc.). Doing them on CCR makes them more dynamic, but you have many more options to mitigate them. That, and the fact that CCR's are much, much more effiicient and flexible than OC, is why they are gaining popularity. But I wouldn't call them the wave of the future for recreational diving.

    Here's a quick break-down on the dangers that you would never have to think of in recreational diving:

    1) They can kill you in 30 feet of water in several ways; hypoxia- not enough O2, hyperoxia- too much O2, hypercapnia- too much CO2
    2) Right now, there is no reliable way to measure CO2 in the loop. You can be breathing happily along, well within the limits of the unit and BANG- CO2 hit that you never saw coming. CO2 is a very dangerous gas and this is extremely difficult to recover from. So if you pack the scrubber incorrectly, you can take a hit. If the sorb settles wierd on the way to the dive site, you can get breakthrough and take a hit. If you forget an o-ring, you can take a hit. The inspo/ evo vision has a temp stick that uses a secondary reaction to guage scrubber life and there are a few fledgeling technologies that hold some promise, but this largely remains a guessing game.
    3) The O2 sensors that we all use were not designed to be used in rebreathers. The leading supplier just pulled out of the rebreather market due to law suits. Current-limited cells can be deadly. Doing a long dive that builds up condensation will have your cells reading low and slow, sometimes really low. So you have to know enough about your unit to fly it properly in its current condition and pad your deco and CNS tracking accordingly. This is why most units have 3-4 cells. You need to implement voting logic and cross-checking in order to have a good guess at what you are breathing.

    Lot's of inexperienced and/or ill-trained people have perished on CCR's. But lots of very experienced, very well-trained, and well-respected divers have also perished on CCR's. We usually never find out the cause and it's often blamed on medical events.

    Compare this to filling an AL80, throwing it on your back and going diving.

    Now let's look at the operational aspects:

    1- Diving prep. Pack the scrubber(s), get gas, analyze gas, assemble the unit, stereo check on the DSV, positive/ negative check, test every function on the unit, then calibrate. Any one of these things can go wrong and then you are off trouble-shooting to get it right. My rEvo has been very reliable in this aspect, but I have several friends who are not so lucky.
    2- Pre-dive. Start up the unit, flood the loop with o2 and make sure the calibration held. Pre-breathe the unit for 5 mins to ensure everything is working propertly. When you jump in, do a 20ft linearity check at 20ft (if you're smart) to ensure your cells are up to snuff. Then you can go dive. The only things you have to worry about during the dive are monitoring and maintaining your PO2 levels, O2 pressure, dil pressure, scrubber duration, and bail-out supply.
    3- Post-dive. You have to break the unit down and clean it after a day of diving. This doesn't really take a lot of time but you have to do it religeously. Disinfect the unit every few days of diving (if diving multiple days, otherwise I do it everytime).
    4- Skills maintenance. There are a few dozen skills you need to stay on top of to be proficient at CCR diving. You can't dive once or twice a year and expect to have fun on one of these things.

    Compare this to filling an AL80, throwing it on your back and going diving.

    Now let's look at the practical aspects:

    1- Cost. CCR's cost WAY more in every way, shape, and form than recreational OC diving. And unless you are diving helium on a regular basis, they are more expensive than CCR's as well. On top of the unit and training cost, you have to pay for all of the consumables; dil and O2, cells, sorb, batteries, disinfectant, it all adds up.
    2- Time. Time to set up, prepare to dive, and break-down after diving are ridiculous compared to OC recreational diving. Plus if you travel with the thing, you will spend a lot of time organizing logistics. CCR divers are treated like lepers just about everywhere.

    Compare this to filling an AL80, throwing it on your back and going diving.

    So this is just something to think about before jumping on the bandwagon. Don't get me wrong, CCR diving is very rewarding and it is a game-changer for technical diving (deep, wreck, caves, etc.). If I had to do it all over again I would, but there is sooo much more to consider than the cool factor. Put it this way, if I can do the dive on a single 80 and I'm out to dive for fun, I'm not doing it on a rebreather. Just my $.02.
  10. lemon

    lemon Contributor

    My CCR instructor likes to compare diving CCRs with what it was like diving OC decades ago - things are primitive. Hopefully things will continue to improve and the technology will develop.

    In terms of C02 hits, I think that pre-packaged cartridges make a lot of sense from a safety perspective. Many will balk at the cost but I think that solid state cartridges like the extendair and prepackaged sorb cartridges like the sofnodive 797, properly used, are a good idea. Increased use of cartridges could decrease user error in sorb packing.

    I also really like the new approach to O2 cells that Bill Stone incorporated into the Poseidon cis-lunar mk6. The unit is designed to automatically perform an auto-validation and calibration on the cell every 5 minutes by blasting small quantities of known gases over the cell and verifying that the cell is reading an appropriate Po2 given known gases and depth. I think this is an advance over the traditional method of putting in 3 cells (or more) and trying to guesstimate your po2 during a dive via either averaging, voting, or elimination algorithms (all of which have inherent flaws.)

    here's an older 2008 interview with bill stone discussing the poseidon which gives a nice overview of how the unit is aimed at sport diving depths, etc.

Share This Page