Should I try a rebreather?

[AJ]

The number of OC dives FAR outnumbers the number of CC dives, however the risk profile of the dives typically done with a rebreather is SIGNIFICANTLY higher than on OC dives.

I'am not a rebreather diver (yet), but as far as I can tell you're more likely to hurt or kill yourself with a rebreather because of it's unforgiving nature. If you screw up on OC you probably get out without too much damage (in case of no serious deco), with a rebreather the outcome can very different making the same kind of mistake. Even with very benign/shallow dive profiles a rebreather is more unforgiving than OC.

Maybe rebreather divers can tell me if I'am right or wrong about this?

 

[Protondecay123]

Sure, but you have to look at it in a reasonable context.

The number of OC dives FAR outnumbers the number of CC dives, however the risk profile of the dives typically done with a rebreather is SIGNIFICANTLY higher than on OC dives. Let's say there are 1000 OC dives every day. If 998 of those dives are recreational NDL dives, and only 2 are mixed gas decompression dives, compared to say 10 CC dives per day, 8 of which are mixed gas decompression and/or cave dives, the comparison falls apart.

Obviously I pulled those numbers out of thin air, but it illustrates the point.

Yes. Illustrative of the point that CCR's are used in a higher risk environment that OC SCUBA could not. That would subsequently lead to a higher rate of incidents. Baghdad versus Beverly Hills.
@rjack321 - Thank you for the movie recommendation! I will certainly watch it. Certainly enjoy foreign film, subtitles and all.
@Gareth J - Thank you for the Richard Pyle recommendation. Loaded into iBook as we speak.

 

[Gareth J]

Rebreathers are curious things.

Whilst they can bite when abused. Unlike open circuit, they generally give you time to analyse and resolve the problem. In fact, that can be the main problem, rebreathers generally kill you slowly. Where as most OC failures are instantaneous, they give gas..... or they don't!

 

[Protondecay123]

Rebreathers are curious things.

Whilst they can bite when abused. Unlike open circuit, they generally give you time to analyse and resolve the problem. In fact, that can be the main problem, rebreathers generally kill you slowly. Where as most OC failures are instantaneous, they with give gas..... or they don't!

Gareth, my sincere thanks for providing the Richard Pyle document! It is flat out Golden. Clear, Concise and very well written. Should be required reading for anyone considering or using CCR in my humble opinion.

 

[Gareth J]

What I like about the Pyle document, is that not only is RP very experienced, and very knowledgeable, but he is quite happy to point the finger at himself.

He clearly explains the mistakes he made, where he went wrong, and how much of an idiot he was in that particular instance. If more people left their ego behind, and admitted their mistakes, we would all learn more.

Anyone who hasn't made a mistake, or done something stupid, who dives regularly, is lying!
I am afraid I have made a few, both on OC and CC.

 

[doctormike]

I'am not a rebreather diver (yet), but as far as I can tell you're more likely to hurt or kill yourself with a rebreather because of it's unforgiving nature. If you screw up on OC you probably get out without too much damage (in case of no serious deco), with a rebreather the outcome can very different making the same kind of mistake. Even with very benign/shallow dive profiles a rebreather is more unforgiving than OC.

Maybe rebreather divers can tell me if I'am right or wrong about this?

One point to be considered, in addition to the "apples and oranges" point made upthread, is that there are situations where a rebreather will increase safety when compared to OC. For example, entanglements, entrapments, silt-outs, navigation errors in overhead (cave and wreck) environments.

But I certainly don't mean to minimize the risks of CCR. If you are going to dive one, you really need to commit to compulsive training, experience, gear maintenance, and best practices. With a rebreather, you can absolutely have a fatal accident in waist deep water.

 

[sunnyboy]

The rebreather needs a lot more surface attention than open circult. In fact, many of the rebreater incidents started long before the dive during assembly or pre-dive checks.

You can get away with 'doing less' in recreational open circuit most of the time (shoudn't, but can) but you really can't get away from the need to do thorough and meticulous checks before diving a rebreather.

But once underwater? I agree that in many situations, the rebreather gives you a lot more time to sort things out.

 

[kelemvor]

I thought of Rob Stewart with the Flooding Scenario on that PDF.

If you read the details, it sounds like the incident Brad's site references is of caustic cocktail. From what I know of the rob Stewart incident, he passed out and drowned due to having low ppo2 (appropriate for depth) in his loop at the surface. If I recall correctly, flooding was cited as the reason he sank. Even if he hadn't sank, I can't imagine surviving while unconscious in the water unless you're wearing a pfd.

 

[rjack321]

Rebreathers are curious things.

Whilst they can bite when abused. Unlike open circuit, they generally give you time to analyse and resolve the problem. In fact, that can be the main problem, rebreathers generally kill you slowly. Where as most OC failures are instantaneous, they give gas..... or they don't!

They can kill you plenty fast, I consider minutes to be "fast"
Brian Bugge died in Hawaii a couple months ago in a couple minutes (on the surface with his O2 off)

 

[Gareth J]

They can kill you plenty fast, I consider minutes to be "fast"
Brian Bugge died in Hawaii a couple months ago in a couple minutes (on the surface with his O2 off)

The surface has always been an area of high risk on CCR.
There does seem to be a recurring issue of CO2, which is often put down to working hard on the surface, swimming against current , failure to pre-breath, etc. Similarly low PO2 problems due to failure to turn the unit on or the O2.

What often puzzles me is how you can miss a low PO2 alarm. Granted, a hypoxic dil can be a contributing issue. However, the scream buzzer and red flashing light should give you a good idea you have an issue (at least on my unit). However, I have dived with the odd person who struggle to hear the alarm, and who's eyesight leave a lot to be desired.
I must admit I find the newer colour handset a major improvement with respect to readability compared with the old monochrome display I had.

With most people I've found them disciplined when it comes to unit assembly and initial post assembly checks.
It is often the rush for the second dive where people are less disciplined, and I have to accept that I have fallen into this trap as well. This is where I, and others have entered the water with the O2 off, having turned it off after the first dive. There is significant risk if you stay on the surface or are working hard and don't rectify this. If you are descending, the PO2 is rising, so you have more time. It shouldn't happen, but it does.
The fact that more units now come with a BOV as standard is a major improvement. But you do need to remember if they are plumbed into the onboard DIL you have very little gas on OC.

During a dive I have often found that I 'zone out' the steady green HUD, but as soon as it starts to flash, or I get a red I become very aware very quickly.

The other area of risk is ascent, when the PO2 is dropping.
(Descent has rising PO2, which has its own issues.)

Like many, I have fallen into the trap of allowing task loading to distract me from the unit itself. Having been made aware of my failure by a change on the HUD, well before the alarm has gone off. Carrying a camera adds to the risk of task loading. But it has normally been contributing factors on the dive, poor vis, navigation, buddy monitoring etc. Like it's often said, it's easy to dive (OC or CC) when conditions are good, the difficulty comes when the conditions are bad, or things start to go wrong.


Gareth