Options for rec divers

[wedivebc]

An RB can kill you plenty dead well within recreational limits. A good friend of mine, Paul Blanchette, who had extesive experience deeper than 300 feet, died on the wreck of the Chester Poling early this summer.

The incident was ultimately found to be caused by diver error, despite the fact that Paul was one of the most meticulous divers I ever met.

The Poling is only 90 feet.

I won't debate the events of Paul's death here because Paul was a friend of mine also and he did a stupid thing that no rebreather diver should have.

I've never dove a rebreather and was wondering. A lot of (higher-end) rebreather training seems to require (prior) deco knowledge and experience, presumably because it's easier to incur deco requirements with them. How much is this an issue with so-called 'recreational' rebreathers, or how does the training for these units deal with depth/time limits? With repetitive multi-level dives, do you end up being more reliant on the dive computer than on OC? Or are these types of units heavily dependent on computers to operate them, and the added risk of depending on them for nitrogen loading is relatively small?

The training for the rec type rebreathers leans more toward knowing the unit's functionality and safe operation and less on survival modes. When recreational diving there is one appropriate response to any perceived problem 'bail out'. In technical rebreather training there is more "if this happens do this" type of responses. Deco training iss not required for recreational RB training and although you can get yourself well into deco before your gas supply runs low the diver must be observant of their limits. Multi level dives can easily be planned using desktop software or even a nitrox computer and this planning is covered in the course. I have included an OC multilevel profile and the same profile on CCR. As you can see the OC profile requires over 8 min of deco even using 30% nitrox. The CCR profile has just 1 minute of deco using air diluent. Also note the gas requirement for dive 1. It would be considered a technical dive on OC but is a recreational dive on CCR.

Speaking for the ISC Predator type RB the philosophy behind it is a very simple RB with very simple operation. The Poseidon RB that TS&M speaks about takes the opposite approach. Very complex electronics which does everything for you (as long as it works)

Consider the following 2 profiles:

Decompression model: VPM - B

DIVE PLAN
Surface interval = 1 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 2

Dec to 50ft (1) Nitrox 30 50ft/min descent.
Level 50ft 9:00 (10) Nitrox 30 0.75 ppO2, 41ft ead
Dec to 100ft (11) Nitrox 30 50ft/min descent.
Level 100ft 19:00 (30) Nitrox 30 1.21 ppO2, 85ft ead
Asc to 80ft (30) Nitrox 30 -30ft/min ascent.
Level 80ft 20:00 (50) Nitrox 30 1.03 ppO2, 67ft ead
Asc to 20ft (52) Nitrox 30 -30ft/min ascent.
Stop at 10ft 8:20 (61) Nitrox 30 0.39 ppO2, 5ft ead
Surface (61) Nitrox 30 -30ft/min ascent.

OTU's this dive: 55
CNS Total: 18.8%

113.6 cu ft Nitrox 30
113.6 cu ft TOTAL


DIVE PLAN COMPLETE

Same dive on CCR

Decompression model: VPM - B

DIVE PLAN
Surface interval = 1 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 2

Dec to 50ft (1) Diluent Air 1.20 SetPoint, 50ft/min descent.
Level 50ft 9:00 (10) Diluent Air 1.20 SetPoint, 23ft ead
Dec to 100ft (11) Diluent Air 1.20 SetPoint, 50ft/min descent.
Level 100ft 19:00 (30) Diluent Air 1.20 SetPoint, 86ft ead
Asc to 80ft (30) Diluent Air 1.20 SetPoint, -30ft/min ascent.
Level 80ft 20:00 (50) Diluent Air 1.20 SetPoint, 60ft ead
Asc to 10ft (53) Diluent Air 1.20 SetPoint, -30ft/min ascent.
Stop at 10ft 1:00 (54) Diluent Air 1.20 SetPoint, 0ft ead
Surface (54) Diluent Air -30ft/min ascent.

OTU's this dive: 72
CNS Total: 25.5%

 

[battles2a5]

In a recreational environment and when used as per manufacturers guidelines and with proper training a RB is quite safe.

With all due respect, I think this is a very misleading statement. With the proper training and mindset dives can be conducted safely on a rebreather. But there is nothing about a rebreather that is inherently safe. If an OC diver observes the MOD of their gas, they will never be at risk of acute hyperoxia, hypoxia, or hypercapnia. They will never have the set of failure modes that a CCR has. CCR carries with it a set of risks and required competence that most recreational divers cannot handle.

I liken this to flying vs. driving. Anybody can drive a car. Lots of people can be trained to fly, but it takes a lot of time, money, and commitment to do it safely. If you build a plane that would be as easy to fly as a car is to drive, everything would be fine until it wasn't. There is only so much that can be dumbed down, but you can never replace the need for skill and competence to get yourself out of an emergency. And if people start buying them and flying them to destinations that could be reached by car just as easily but at a much lower cost then all the risk and accidents would be very hard to justify. Again, just my $.02.

 

[kanonfodr]

With all due respect, I think this is a very misleading statement. With the proper training and mindset dives can be conducted safely on a rebreather. But there is nothing about a rebreather that is inherently safe. If an OC diver observes the MOD of their gas, they will never be at risk of acute hyperoxia, hypoxia, or hypercapnia. They will never have the set of failure modes that a CCR has. CCR carries with it a set of risks and required competence that most recreational divers cannot handle.

I liken this to flying vs. driving. Anybody can drive a car. Lots of people can be trained to fly, but it takes a lot of time, money, and commitment to do it safely. If you build a plane that would be as easy to fly as a car is to drive, everything would be fine until it wasn't. There is only so much that can be dumbed down, but you can never replace the need for skill and competence to get yourself out of an emergency. And if people start buying them and flying them to destinations that could be reached by car just as easily but at a much lower cost then all the risk and accidents would be very hard to justify. Again, just my $.02.

I am sigging that. Thank you!!

Peace,
Greg

 

[slackercruster]

Thanks for the great feedback.

What prompted my question was an article I read (albeit rushed) last year. It was in a publication PADI puts out for dive shops.

It said the industry was to make rebreathers more safe and less expensive to introduce them to rec divers. Gave a long wish list of safety options it wanted in CC. From your posts it seems they are far from the inexpensive rec model goal.

I searched for the mortality rates here and on google. Can't seem to find them. Do CC divers die 2 to 1 compared to OC?

What about old style rebreathers? A DM told me had used a very simple model back in the day. Didn't give me any names. But said they had ruined rebreathers making them too complex.

 

[Web Monkey]

Have rebreathers been simplified and downsized in price for recreational divers yet? If so, how much does it cost to get in to a basic model?

They're pretty small and not all that complicated, but much too unforgiving of diver error to be useful for recreational diving.

Depth really isn't an issue. Someone actually died in a pool recently (past year or two) on a rebreather.

Terry

 

[kidspot]

I've never dove a rebreather and was wondering. A lot of (higher-end) rebreather training seems to require (prior) deco knowledge and experience, presumably because it's easier to incur deco requirements with them. How much is this an issue with so-called 'recreational' rebreathers, or how does the training for these units deal with depth/time limits? With repetitive multi-level dives, do you end up being more reliant on the dive computer than on OC? Or are these types of units heavily dependent on computers to operate them, and the added risk of depending on them for nitrogen loading is relatively small?

There are actually 2 "starting" point classes for Rebreathers (at least with IANTD)

1) Recreational Closed Circuit Rebreather which can be taken as an initial open water course (no diving experience necessary) or as an open circuit to closed circuit class. Either one requires basic Nitrox (may be taken in conjunction with the course)

2) Closed Circuit Rebreather Diver - Advanced nitrox is required either prior or in conjunction with the course.

In both cases note that nitrox is a requirement - because when dealing with a rebreather you are dealing with Nitrox (albeit an ever changing nitrox blend) - Personally I think having Advanced Nitrox first is a good idea as a rebreather can offer up to 100% O2 while diving, and the implications of this are not covered much in a basic Nitrox course (usually they are limited to 40% blends).

To the OP - I almost hate to bring it up at this point in time, as it's hitherto in 'limbo' but the Open Safety Apocalypse IV iCCR is targeted at the recreational entry crowd as well, with a reasonable (for CCR's at least) price point of $3k + Training. Until it is released (hopefully soon ... as someone who has a deposit on one) there is no way of telling if it will fill this niche in the marketplace or not. The side benefit is that it is also capable (on paper at least so far) without modification of 250ft dives using helium blends, so it offers room to grow with for the aspiring technical diver. One of the big differences between it and other rebreathers is that it automatically bails the diver onto open circuit if the breathing mix is unbreathable - of course a LOT of current rebreather divers have expressed a great deal of concern over this concept.

Aloha, Tim

 

[ScubaDadMiami]

I have to respectfully dissent from your views here a little although I suspect this could just be a matter of some phrases chosen rather than your intent. For example:

But there is nothing about a rebreather that is inherently safe.

There is nothing about a rebreather or open circuit gas delivery system that is, as you stated, "safe." (In fact, nothing in life is "safe" including just staying in bed your whole life.) True, the rebreather is a more complex piece of equipment. However, either will kill the diver just as dead if not used properly. With training and a diver that uses the skills learned in that training, both manage the risk of diving. In fact, as Tom Mount has said, a CCR can actually be safer than open circuit when used by a diligent diver. In the end, it is the diver that makes the difference.

If an OC diver observes the MOD of their gas, they will never be at risk of acute hyperoxia, hypoxia, or hypercapnia.

Again, not exactly accurate. There are instances of all of these events happening on open circuit. For example, there are people that have "toxed" with a PO2 that is considered a low risk of hyperoxia. There are people that have breathed a hypoxic gas mix in the shallows. There are instances of people that have overbreathed regulators, resulting in hypercapnia. Likewise, there have been accidents on closed circuit related to the same issues.

They will never have the set of failure modes that a CCR has.

Agreed. Each has different procedures for the various failures that can occur. A CCR can be more complex because there are aditional avenues for failures beyond open circuit.

CCR carries with it a set of risks and required competence that most recreational divers cannot handle.

"Cannot" and "choose not to" are not the same thing. Any diver that is willing to put in the training and time can learn either set of skills. Granted, there are more skills required for CCR. So, there is additional time required to learn the skills, and there will be additional time to practice in order to remain proficient. The truth is that most recreational divers never practice skills after initial training.

I liken this to flying vs. driving. Anybody can drive a car. Lots of people can be trained to fly, but it takes a lot of time, money, and commitment to do it safely. If you build a plane that would be as easy to fly as a car is to drive, everything would be fine until it wasn't. There is only so much that can be dumbed down, but you can never replace the need for skill and competence to get yourself out of an emergency. And if people start buying them and flying them to destinations that could be reached by car just as easily but at a much lower cost then all the risk and accidents would be very hard to justify. Again, just my $.02.

I won't disagree with the intent of this last statement. Diving a CCR definitely takes time and practice. It also takes the mindset to pay attention to what is going on while using it. If you are not a diver that is willing to spend the extra time that will be required to remain proficient, you do not want to get involved in rebreather diving.

 

[battles2a5]

There is nothing about a rebreather or open circuit gas delivery system that is, as you stated, "safe." (In fact, nothing in life is "safe" including just staying in bed your whole life.) True, the rebreather is a more complex piece of equipment. However, either will kill the diver just as dead if not used properly. With training and a diver that uses the skills learned in that training, both manage the risk of diving. In fact, as Tom Mount has said, a CCR can actually be safer than open circuit when used by a diligent diver. In the end, it is the diver that makes the difference.

I never claimed OC was safe, I was reacting to the comment stating that RB diving was safe. While both have inherent dangers, it is impossible to say to CC is anywhere near as safe as OC. Tom Mount has said a lot of things about CCR, and more than one of them have been controversial . In the end, for the vast majority of divers (especially recreational divers) OC diving is much safer IMO. There's always an exception, I am speaking in generalities.

Again, not exactly accurate. There are instances of all of these events happening on open circuit. For example, there are people that have "toxed" with a PO2 that is considered a low risk of hyperoxia. There are people that have breathed a hypoxic gas mix in the shallows. There are instances of people that have overbreathed regulators, resulting in hypercapnia. Likewise, there have been accidents on closed circuit related to the same issues.

Agree, there have been instances. But these are very rare and have more to do with the physiology of that specific diver than it does the mechanics of the system they are diving. So while there may be cases of these things happening, it is not something that a OC diver really has to consider other than obeying a MOD. A CCR needs to be in on top of this at all times.

Perfect example is when the Poseidon Mk6 came out. Within the first few weeks a guy went lights out on the surface because he went hypoxic. Some say it was a training issue, some say it was an electronics issue, most agree it was both. But the simple act of jumping in the water and swimming to the tag line almost cost the guy his life. This is not something you need to think about on OC.

"Cannot" and "choose not to" are not the same thing. Any diver that is willing to put in the training and time can learn either set of skills. Granted, there are more skills required for CCR. So, there is additional time required to learn the skills, and there will be additional time to practice in order to remain proficient. The truth is that most recreational divers never practice skills after initial training.

I guess it depends on how you look at it. I wouldn't consider the vast majority of the rec diving set willing to put in the time and practice to dive a rebreather. Going out and actively practicing drills, tearing down and rebuilding the rig, etc. You need to dedicate a good amount of time to do this stuff. So whether it's cannot or will not, it all has the same result.

Diving a CCR definitely takes time and practice. It also takes the mindset to pay attention to what is going on while using it. If you are not a diver that is willing to spend the extra time that will be required to remain proficient, you do not want to get involved in rebreather diving.

I couldn't agree more. I will also add that CCR diving is extremely rewarding. It opens your diving up to a whole new world. You just need to be prepared to devote the time, energy, and training in order to take advantage of what a CCR can offer. I'm a huge fan of CCR, just skeptical of the recreational CCR movement.

 

[padiscubapro]

An RB can kill you plenty dead well within recreational limits. A good friend of mine, Paul Blanchette, who had extesive experience deeper than 300 feet, died on the wreck of the Chester Poling early this summer.

The incident was ultimately found to be caused by diver error, despite the fact that Paul was one of the most meticulous divers I ever met.

The Poling is only 90 feet.

I was a friend of Paul and don't want to disparage his name, but the fact is he was doing a recreational depth dive, treated it as such, but was using a hypoxic trimix (not breathable to about 20 fsw) without a surface breathable bailout gas... Doesnt sound like recreational to me.. This was also Paul's first dive of the year after a very long lay off.. a 90fsw dive is not exactly a good choice to get rid of the cob webs regardless of ones experience....

 

[slackercruster]

Thanks Tim.

Think they should have chosen another name than Apocalypse!

What about used units? Or are used rebreathers even more dangerous?