Recreational Rebreathers

[jmsdiver]

I have read King_Neptunes glowing review of several rebreathers out there; I have read several of the threads here on the board. One of the threads stated something to the effect that using rebreathers "recreationally" is probably not the best use of a rebreather.

1) I guess the question is why not?

2) Furthermore, what are the opinions on recreational rebreathers, say like the Drager line (are there others)?

3) How do they differ from a technical rebreather?

I've been looking but not ready to take the plunge just yet. I see advantages and disadvantages of it and for the type and area that I would be diving I don't know if there is a serious advantage due to water temp (can't really stay down for hours in 38F water you know).

Tanks again all

 

[padiscubapro]

Originally posted by jmsdiver
I have read King_Neptunes glowing review of several rebreathers out there; I have read several of the threads here on the board. One of the threads stated something to the effect that using rebreathers "recreationally" is probably not the best use of a rebreather.

1) I guess the question is why not?

2) Furthermore, what are the opinions on recreational rebreathers, say like the Drager line (are there others)?

3) How do they differ from a technical rebreather?

I've been looking but not ready to take the plunge just yet. I see advantages and disadvantages of it and for the type and area that I would be diving I don't know if there is a serious advantage due to water temp (can't really stay down for hours in 38F water you know).

rebreather are exothermic (they create heat) so you are breathing warm air rather than air at ambient.. if you are working the air gets really warm.. I did a dive a few weeks ago where the bottom temp was abut 36f and I was hot in my drysuit, we were really covering some area so I was generating a higher than normal co2 level so the scrubber was really going , my guess is that the inspired air was around 100f

 

[Diverl]

Originally posted by jmsdiver
I have read King_Neptunes glowing review of several rebreathers out there; I have read several of the threads here on the board. One of the threads stated something to the effect that using rebreathers "recreationally" is probably not the best use of a rebreather.

1) I guess the question is why not?

2) Furthermore, what are the opinions on recreational rebreathers, say like the Drager line (are there others)?

3) How do they differ from a technical rebreather?

There are several key advantages to a rebreather that make it an excellent choice for exceeding recreational dive limits. the most important being that a rebreather has exceptional gas effeciency that is independant of depth; theoretically a diver could spend significant time at depth comsuming thier gas supply as if they were very shallow. The second major advantage of a rebreather is its ability to maintain a divers pp02 constant regardless of depth (Depending on model). This is significant especially when diving deep, open circuit scuba would require using several different gas mixtures ie travel gas, bottom gas and deco gas. A rebreather could eliminate the use of all of these cylinders and gas mixtures allowing for faster decompression and safer pp02. Will a rebreather do anything for the average recreational diver, you bet, but the gains are not nearly as significant as for the deep diver. With the cost of the rebreather itself and then the scrubber chemicals it is deffinatly more expensive to dive and requires a lot more prep and cleanup work for a dive that can probably be made on a single al80 or 100. Basically if you stay within the recreational time and depth limits, you would probably have to make very long shallow dives to get significant benifits from a rebreather. Everything else you could probably make using air or nitrox at a fraction of the cost and a lot less training and time would be involved. Don't let me discourage you, I am by no means an expert on rebreathers. I am sure that someone can give you several good reasons for diving with a rebreather within recreational limits, I just think that they really shine at the greater depths.

The big difference between the technical rebreathers and the recreational rebreathers (If you can actually call them that) are there ability to fully control the pp02. The line on this is usually a fully closed circuit or semi closed circuit rebreather. fully closed circuit rebreathers usually have two cylinders, 100% oxygen and a dilutent bottle (triox, helium, air). semi closed circuit usually have a single cylinder contains nitrox. Depending on the nitrox mix that you put in the clyinder you put a different sized orifice into the unit controlling the pp02. The pp02 is not really being controlled, not allowing hte diver to dive as deep or as long.

I have never used a rebreather so I am no expert. I dove with a guy who has one (Buddy Inspiration) and he swears by it. He is a videographer and dives very deep, for long periods of time. He says he would only ever buy a fully closed circuit rebreather.

Rebreathers
Dragar Ray, Dolphin
Azimuth Cyclic
Halcyon 80
Frog
Buddy Inspiration
Prism Topaz
Megalodon

All these were found in the October 2001 issue of Rodales scuba diving magazine; 8 affordable rebreathers. Hope this helps!

keep diving and have fun!

 

[Deputy821]

Rebreathers are fun to dive and that's what diving is all about. You really appreciate a rebreather the first time you dive one in a pool. If you are diving alone on that first dive, or with another rebreather diver, it will seem soooo.. natural. When the open circuit divers enter the water it will be sooo..loud. You will suddenly realize how objectionable open circuit is and you will wonder why anyone would dive with air.

The Azimuth rebreather, unlike most the open circuit rebreathers can be adjusted for any mix. It has two tanks, not one and you'll have all the Nitrox you could want. It has it's own wings and a great weight system. While it is not cheap, it is well built and added expenses like the BC are not needed. Semi-closed circuit are the simplest and do not rely soley on electronics. I am not qualified to comment on closed circuit mixed gas rebreathers so I will leave that to more informed divers. I dive oxygen most of the time. The Azimuth can be dialed in for O2 also.... or any mix you want. It would be good to have an oxy guage installed, but one is not required. Azimuths may soon have a closed circuit modification available.

World War II saw the wide use of oxygen shallow water rebreathers. Six Italian frogmen sank two British battleships anchored in Alexandria Harbor in 1941, using them. Hans Hass used them and was making underwater films before Cousteau was ever heard of. They have been around a long time. The military was the main user. Sport diver's were not offered them because of liability and sport divers were thought to be too stupid to learn their use. Navy divers were all civilians once and the difference is training. Look at WWW.DIVESAFE.NET and Diver Dave's Rebreather site, WWW.Nobubblediving.com.

Steve Taylor

PS> Someone once wrote "they are just a great piece of equipment". If you try one you'll never go back. However, they are not a casual item, for most, the simple open circuit are is just fine.

 

[madmole]

Well, I'm not going back to the open side

CCR Good
1) Warm air
2) No noise (boy is OC loud)
3) Much cheaper per dive (OC twins £12 per fill, CCR fill £14 per weekend 4 dives with Air)
4) Lighter unit
5) More streamline, less drag
6) Less Deco
7) Longer NST (3 hours at 20m!!!!)
8) More bailout and emergency options than OC
9) Adds challenge back into diving after thousands of OC dives
10) Much much cheaper than OC Trimix
11) Longer time underwater

CCR Bad
1) Initial cost (3 x OC twins and stages)
2) The hassle you get from the uninformed and the jelous

CCR indiferent
1) You must do pre dive checks (10 mins max)
2) You need to be able to strip and rebuild it
3) Yearly maintenence costs (sensors etc)
4) Higher skill and theory level required. you should have this already anyway

 

[MikeS]

I’m not sure what the difference are between a recreational versus technical rebreather but I would like to address question number 1 in general.

With a rebreather there are multiple failure modes, both hardware failure and human error, where the first symptom is unconsciousness. While this is true in open circuit also, i.e. O2 toxicity, it is much easier to avoid these situations by proper dive planning.

Diving is inherently dangerous. We all try to mitigate the risk as much as possible through training and equipment, but ultimately we must weigh the risks versus the rewards, and determine our level of expectable risk. I think that anyone that does not acknowledge that rebreather diving, based on current technology, has more associated risk than open circuit is fooling themselves. To validate this, just look at all of the warnings and cautions in the rebreather manuals. From my point of view the increased risk associated with rebreathers is not justifiable.

However, looking toward the future I see a time when through advances in technology rebreather diving will become safer and more common than open circuit. The pioneers of today are helping to develop safer rebreathers for tomorrow.

Mike

 

[deepblueh2o]

Not sure what to think when I read long e-mail responses to questions that relate to rebreathers that end in, " I don't own a rebreather, but if I did ". No, I'm not picking on anyone, I have seen it more than once. I pretty much agree with madmole. I don't consider a semi-closed rebreather to be technical, they just require more knowledge to operate. You had to learn open-curcuit, now learn semi-closed. I haven't a clue how many types of rebreathers there are, not counting home-mades.
The Drager Dolphin has abilities slightly greater than recreational limits. The Drager Ray was designed with warm, shallow water in mind and has greatly reduced limits that can be overcome by only the more technically advanced divers. We call it 'modification', everyone else just calls us nuts.
Both of these Drager models greatly inhance recreational diving and are not in the technical class. If you are diving open curciut and want more, all Drager (now Aqua Lung) dealers that I know of, have what they call intro classes. They are fairly cheap, you get hands on experience, and then you will know if you want to know more.
Yes, I have 2. A modified Drager Ray good to 150' and a home built closed circuit good to 300'. I also do not consider myself a tech diver, they really don't have to be that difficult.

 

[madmole]

Good Example, this weekend

Took a hard boat (with a tail lift ) out of Portland. 12 folks, 2 of us on rebreathers (Chris with very modded Dolphin and me on my insp). Despite those that reckon RB's take lots of prep, we were the first pair in each dive (and the last out!!!)

Did 36m for 45 mins on the Pomeranian (6 mins of stops), and then a 17m for 40mins drift on Pulpit rock (NSD). Then yesterday did 37m for 40 mins (8 mins deco) and then then 18m for 50 mins on the james fennel and another bigger wreck nearby that we drifted onto

So advantages were

1) Longer dives with less decompression penalty. We could have easily stayed even longer (over 1 hour with 14 mins stops)
2) Warm and no dry throat
3) Cost 2xO2 at 6, 2xair at 2, 2xSofnolime at 4 so total of 24 pounds. whereas for OC Nitrox it was 2xtwinset at 12 and 2 x 50% stage deco at 4, so total 32. So CCR cheaper
4) Lighter kit than twins a and stage deco. even though I was carrying a spare 3L Air bailout and a 3L 50% deco mix
5) Wildlife. Are not so bothered by the units. I even manged to touch a Ballan Wrasse. Fish get much closer (shame the Lobbies can still see you coming)
6) No frantic swapping of cylinders between dives

These were normal club dives and I would class them as recreational rather than technical. 2 of the club were on Single 15's (they got 15 mins on the wrecks) and needed a second tank for the afternoon dive

My rebreather suits me for recreational diving well and gives me longer times without worrying about gas. Decompression and how much bailout you wish to carry becomes the limiting factor