Cave diving on CC is safer than on OC?

[ofg-1]

I was interested if there is consensus on the topic.

Well, you obviously have not paid attention for the past several years. You could offer a lot of free money and not get a consensus on the currency to be used.

 

[Wibble]

Lack of bailout isn’t what’s killing ccr divers. It’s hypoxia and hyperoxia, and hypercarbia, three things that are much easier to experience on a rebreather.

What causes them then?

Not knowing your PPO2? Not acting on them?

Hypercapnia you would notice. Then your difficulty in switching to bailout and hoping there’s enough for the ride to the surface.

 

[Underwater Tourist]

If you examine the Riviera Maya alone, then perhaps surprisingly, A has more accidents. There are plenty of CCR and SCR divers being done in that area of the world and I can't recall a single fatality. Vs ample OC fatalities.

If you look at someplace the USA, then we've had more far accidents and fatalities on CCR then on OC. Two accidents in Roaring River last year, the double Eagle's fatality plus plenty more.

Then to answer my own OP question, I would say that if you are diving in a system that has complex navigation (so MX style), then CCR definitely does offer more benefits because probability of a navigational error increases meaningfully. Whereas the probability of a CCR failure stays the same.

On the flip side, CCR might not be worth the risk when diving a system with less navigation (Fl style), especially if you can comfortably do the same dive on OC.

 

[rddvet]

What causes them then?

Not knowing your PPO2? Not acting on them?

Hypercapnia you would notice. Then your difficulty in switching to bailout and hoping there’s enough for the ride to the surface.

You or I may notice, but I think the big issue is some people are distracted or oblivous and others ignore early warning signs.

 

[PfcAJ]

What causes them then?

Not knowing your PPO2? Not acting on them?

Hypercapnia you would notice. Then your difficulty in switching to bailout and hoping there’s enough for the ride to the surface.

Plenty of people have not noticed or not acted. Same with co2. You get into a respiratory feedback loop and you’re toast.

On OC, your gas doesn’t change on you outside of literally taking the reg out of your mouth and putting a different one in. You certainly can f that up, but the equipment itself isn’t going to do it for you.

 

[Vicko]

How many people do you see doing risky dives on OC?
And how many people with less than 5 years of experience do you see doing 200m dives or 3km penetrations?

OC is simple, the rules are simple, the execution is simple.
CC is not, but it does make previously risky dives look benign because you think you have all the time in the world to solve problems. And then you drown 10m from the entrance because you just injected 10/60 or something into your loop, while chest deep in water.

 

[Wibble]

Plenty of people have not noticed or not acted. Same with co2. You get into a respiratory feedback loop and you’re toast.

On OC, your gas doesn’t change on you outside of literally taking the reg out of your mouth and putting a different one in. You certainly can f that up, but the equipment itself isn’t going to do it for you.

Why don't people notice their PPO2? That's the #1 mantra for diving a rebreather: Always know your PPO2

On OC, you always need to do a NoTox drill when switching regulators on OC. Plenty of failures with that as well as mis-analysing or mis-labelling gas.

At least on a box you ride it to the surface, continually adjusting the PPO2 as you go, no gas switching required.

You or I may notice, but I think the big issue is some people are distracted or oblivous and others ignore early warning signs.

Which is a training issue? Definitely an experience issue.

Arguably it's an issue when diving a full electronic CCR as you get more complacent that the computer will sort things out: if something's virtually always OK, you don't notice when it isn't. One hopes that people diving manual or hybrid rebreathers would be very aware of their PPO2.

 

[rjack321]

Why don't people notice their PPO2? That's the #1 mantra for diving a rebreather: Always know your PPO2

The same reason(s) they inadvertently do visual jumps, or spend so long taking video of the pretty formations that they don't have enough OC gas to exit.

 

[billgraham]

The same reason(s) they inadvertently do visual jumps, or spend so long taking video of the pretty formations that they don't have enough OC gas to exit.

I don't know anyone who hasn't inadvertently done a visual jump! Diving the CCR is much nicer when something goes awry, you have plenty of time.

On OC, you always need to do a NoTox drill when switching regulators on OC. Plenty of failures with that as well as mis-analysing or mis-labelling gas.

At least on a box you ride it to the surface, continually adjusting the PPO2 as you go, no gas switching required.

There were many, many "wrong gas" fatalities that I am aware of, and this is a good point. The battle with the CCR is not falling asleep on deco when it's warm because you're doing almost nothing.

 

[rddvet]

I will make this easy to understand. The general population of the US and probably the rest of the world are oblivious morons. There are many of these morons that have the money and desire for a ccr. Many of these morons you’ve probably seen at sites or dove with because they’re ubiquitous.
Once you realize most of us are stupid and that no human is infallible, the quicker you’ll (generlized you) understand why people who are taught to monitor their po2 don’t amongst other things like not checking gases