Why no poor man's rebreather?

[sea_ledford]

Again, it's not CO2 sensors or O2 sensors that are killing people. It's people diving with known bad sensors, or forgetting to turn their oxygen/computer on. Or, they are diving stuff they are brand new at, or not qualified to dive. For example: A relatively new CCR diver completing his trimix and CCR cave, then dying days later in a 300' deep in super restrictive cave.

I didn't say that is what is killing people, those are just the known common failure points, and that hasn't really changed since they started using voting logic. Having three fairly unreliable O2 cells that need to be replaced annually is just a pain in the ass. Sure they are great when they work, but if they get too hot, they are dead, if they get too wet they don't work, they may work well enough for you to think they work, but they really don't work. That is why the Revo has like 15 of them.

And a lack of CO2 monitoring is the thing I expect we'll look back on in 20 years and say, "Man, I can't believe we used to dive that way! We were idiots."

But I agree that over confidence in ones skills and not using checklists appropriately is much more likely to get them dead than a failed sensor or scrubber breakthrough.

-Chris

 

[Schwob]

Here it is, cheaper than just a tank:

A $100 HOT WATER BOTTLE PENDULUM REBREATHER

Anybody know of a link to this that works today?
@herman ?

 

[JohnnyC]

One of the biggest impediments to low-cost rebreathers is the economy of scale. Look at how many rebreathers are on the market, there's a thread over on CCRx with people posting their JJ numbers. There are like, 200 of them. That's it. And that's with one of the more popular units on the market currently.

The cost of machine time and components and R&D at such a small scale isn't cheap. My Pelagian was built in a garage in Thailand, the dude still wants something like $6000 for them new, and they're in the 150+ number of units out there. A JJ is running Shearwater electronics and BMCL's. Those are two things they didn't have to develop themselves, and they're still $$$$. Point is, even without having to design everything involved, the cost is still expensive to develop and produce.

AP have the most successful business in terms of units sold. They pioneered rebreathers in the recreational diving world, and they're still not in everyone's dive locker. Until rebreathers can be produced and sold on a scale that rivals the modern day second stage regulator, they will always be prohibitively expensive to most recreational divers.

Now all of that is ignoring the substantial investment in training required to dive one, or the safety implications of being a poor rebreather pilot, both of which add another level of cost and complexity to the equation.

 

[herman]

Anybody know of a link to this that works today?
@herman ?

Tom died a few years ago (natural causes, nothing dive/rebreather related). He was a great guy and a pleasure to know. I assume his web page was pulled down shortly after that so no, it is not active.

 

[Schwob]

Tom died a few years ago (natural causes, nothing dive/rebreather related). He was a great guy and a pleasure to know. I assume his web page was pulled down shortly after that so no, it is not active.

Thanks ... & sorry to hear.

 

[Superlyte27]

I didn't say that is what is killing people, those are just the known common failure points, and that hasn't really changed since they started using voting logic. Having three fairly unreliable O2 cells that need to be replaced annually is just a pain in the ass. Sure they are great when they work, but if they get too hot, they are dead, if they get too wet they don't work, they may work well enough for you to think they work, but they really don't work. That is why the Revo has like 15 of them.

And a lack of CO2 monitoring is the thing I expect we'll look back on in 20 years and say, "Man, I can't believe we used to dive that way! We were idiots."

But I agree that over confidence in ones skills and not using checklists appropriately is much more likely to get them dead than a failed sensor or scrubber breakthrough.

-Chris

I don't know what to say. My cells work every dive. Lol. I live in hot humid Florida. I have over 2000 hours between 5 different units and the only rebreather that almost killed me was a Revo that flooded. Which is why I only dive CCRs that can recover from a flood now. Changing cells is a pain in the butt, but a lot quicker and easier than overhauling a regulator. Yet we do this without fuss.

 

[Superlyte27]

Also, all five of the units I'm certified on have CO2 monitorong. It's MY BRAIN. Pack your scrubber right. Follow the guidelines for duration and you've got nothing to worry about. Your brain will tell you if you have breakthrough. You just have to watch for it. Is your breathing rate increased or labored? You can tell. If so bailout.

 

[sea_ledford]

Unfortunately, one of the early signs of hypercapnia is decreased neural function, so depending on your brain isn't the greatest solution. But hey, I do it too, it is what we have available currently. And I don't know a single CCR diver that actually follows the scrubber duration recommendations. Primary because they are tested and rated under unrealistic conditions for most of us, so it doesn't really apply. But that means we are left with extrapolating usable time before we even get wet. And if it is dependent on packing your scrubber right, it isn't a very robust system. If humans excel at anything it is finding new and novel ways to screw things up.

It seems like you think I am saying CCRs are dangerous death traps. That isn't what I am saying at all, in fact in many situations, I think CCRs are safer than OC. O2 sensors and lack of CO2 monitoring are just the weak links in the system. It's great that you have 2000 hours on CCRs and have never had cell issues, but I think that puts you in the minority! I'm jealous!

 

[KevinNM]

One of the biggest impediments to low-cost rebreathers is the economy of scale. Look at how many rebreathers are on the market, there's a thread over on CCRx with people posting their JJ numbers. There are like, 200 of them. That's it. And that's with one of the more popular units on the market currently.

The cost of machine time and components and R&D at such a small scale isn't cheap. My Pelagian was built in a garage in Thailand, the dude still wants something like $6000 for them new, and they're in the 150+ number of units out there. A JJ is running Shearwater electronics and BMCL's. Those are two things they didn't have to develop themselves, and they're still $$$$. Point is, even without having to design everything involved, the cost is still expensive to develop and produce.

AP have the most successful business in terms of units sold. They pioneered rebreathers in the recreational diving world, and they're still not in everyone's dive locker. Until rebreathers can be produced and sold on a scale that rivals the modern day second stage regulator, they will always be prohibitively expensive to most recreational divers.

Now all of that is ignoring the substantial investment in training required to dive one, or the safety implications of being a poor rebreather pilot, both of which add another level of cost and complexity to the equation.

The end-tidal CO2 modules used for medical purposes sell probably millions a year these days. But they are not designed to operate at 10bar in 90% helium, etc. So getting development of affordable CO2 sensors for rebreathers that sell thousands a year is not easy.

 

[Superlyte27]

It just means that I believe in proper maintenance. Have I had cells die for no reason? Yes. Have I had them die while in a cave? Yes. But, certainly not all 4 of them. But even if all four of them died, or even 2 of them died, I'm trained to overcome it. So are my students.

As far as decreased mental capacity during a CO2 event, what happens first? Increased breathing rate to void CO2 or decreased mental capacity? So, if you are vigilant, and make sure your breathing doesn't increase, no worries.

Now, some people suffer from decreased mental capacity before they even get out of the car. My argument is that CCR's are not for everyone. The stupid need not apply.