anti caustic canisters?

[Underwater Tourist]

So I was reading about how awful the recovery is if you are lucky to survive a caustic accident, and thought that it shouldnt be that difficult to make anticaustic canisters

Adding some hydrophobic coating that would let the gas through and not the liquid could be an easy fix, and I doubt that it will completely ruin wob.
Sure maybe for some uber deep dives it will be an issue, but given that you are breathing through layers of sorb to begin with, adding a coating layer should be ok

And I am sure there are a dozen other clever ways to make such a canister

Which raises the question, any particular reason they don't exist?

 

[ClarkJ]

Cis-lunar scrubber

 

[grantctobin]

Cis-lunar scrubber

This^

That said, there are not very many of them and they have a bit of a lifespan. At one point, it was leaked (scuttlebutt?) that the scrubbers could be changed underwater. Unsure if total hearsay or not. If you’d like one @Underwater Tourist , I think Joel Clark is still selling his modified Sidekick with CisLunar scrubber. Afaik the coating does in fact increase WOB measurably but can’t recall the exact extent.

 

[MattK911]

This^

That said, there are not very many of them and they have a bit of a lifespan. At one point, it was leaked (scuttlebutt?) that the scrubbers could be changed underwater. Unsure if total hearsay or not. If you’d like one @Underwater Tourist , I think Joel Clark is still selling his modified Sidekick with CisLunar scrubber. Afaik the coating does in fact increase WOB measurably but can’t recall the exact extent.

Bill Stone told me Richard Pyle had developed a technique for swapping scrubbers on the Cis-lunar while underwater. I meant to ask Pyle about it when I ran into him at DEMA, but completely forgot.

 

[rjack321]

So I was reading about how awful the recovery is if you are lucky to survive a caustic accident, and thought that it shouldnt be that difficult to make anticaustic canisters

Adding some hydrophobic coating that would let the gas through and not the liquid could be an easy fix, and I doubt that it will completely ruin wob.
Sure maybe for some uber deep dives it will be an issue, but given that you are breathing through layers of sorb to begin with, adding a coating layer should be ok

And I am sure there are a dozen other clever ways to make such a canister

Which raises the question, any particular reason they don't exist?

Never been on a CCR before? You are making whole pile of assumptions about how it's so easy to make a gas permeable low WOB hydrophobic membrane. What's your related education and training in this field of engineering?

 

[Underwater Tourist]

Never been on a CCR before? You are making whole pile of assumptions about how it's so easy to make a gas permeable low WOB hydrophobic membrane. What's your related education and training in this field of engineering?

None
Simply asking how bad can it be. For not very deep dives, if the wob increase is not awful, then wouldnt it be a solid tradeoff to eliminate the chance of a caustic?

And the question is not really about a hydrophobic membrane/coating per se, but more about how to block the caustic from reaching the mouthpiece. The membrane was the first example that came to mind as I was typing the question. Perhaps some smart people can come up with a different approach to achieve the same thing. Maybe a combined approach of a semi-hydrophobic membrane (that would not increase wob a lot but still block some of the caustic) + some other measure.

Anyhow, it feels to me that its not something unbelievably difficult to achieve

Afaik the coating does in fact increase WOB measurably but can’t recall the exact extent.

Is that the reason they are not popular?

 

[ClarkJ]

In my experience there was not a significant increase in the work of breathing with the cis-lunar scrubber Until a substantial amount of water was involved. Then the fabric closed and there was no breathing, but better than a caustic, especially with the lithium hydroxide media it was designed for.

joel

 

[SavageSeaCow]

In my experience there was not a significant increase in the work of breathing with the cis-lunar scrubber Until a substantial amount of water was involved. Then the fabric closed and there was no breathing, but better than a caustic, especially with the lithium hydroxide media it was designed for.

joel

Interesting! I did hear that the scrubber was a giant PIA to pack. Was that your experience? What made it challenging?

 

[Superlyte27]

Honestly, there are a few failure modes on a rebreather. Too much O2, too little O2, too much CO2 (breakthru) and caustic.

I have thousands and thousands of hours on a rebreather. I’m certified on nearly every popular rebreather out there and am an instructor on several. I’ve had 4 caustic cocktails in my life, only one of them my fault. But, if I had to choose a failure while CCR diving, I’d choose the caustic. While it sucks, at least you know it’s happening.

I’ll take a problem I can identify immediately over one that can sneak up on you every time.

If I were trying to overcome an inherent problem with CCR, Caustic Cocktails wouldn’t be what got my attention first, or even second.

 

[iliketopetsharks]

Honestly, there are a few failure modes on a rebreather. Too much O2, too little O2, too much CO2 (breakthru) and caustic.

I have thousands and thousands of hours on a rebreather. I’m certified on nearly every popular rebreather out there and am an instructor on several. I’ve had 4 caustic cocktails in my life, only one of them my fault. But, if I had to choose a failure while CCR diving, I’d choose the caustic. While it sucks, at least you know it’s happening.

I’ll take a problem I can identify immediately over one that can sneak up on you every time.

If I were trying to overcome an inherent problem with CCR, Caustic Cocktails wouldn’t be what got my attention first, or even second.

I'm not CCR certified, maybe in the very distant future, but i'm curious: how do you know it is happening? Like a weird taste in your mouth, and higher breathing resistance?