Scrubber duration in warm water

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Workload, personal metabolism and packing consistency all are variable so I appreciate why few manufacturers publish test results with the fear people will accept them without personalization.

Regards,
Cameron

Well, I think that they have to, right? At least for CE units. We need to have some sort of idea what the limit is on the scrubber using defined parameters, and then it's up to the individual diver to decide if the produce more CO2 on a real dive than the scrubber had to handle in the lab.
 
Well, I think that they have to, right? At least for CE units. We need to have some sort of idea what the limit is on the scrubber using defined parameters, and then it's up to the individual diver to decide if the produce more CO2 on a real dive than the scrubber had to handle in the lab.

For CE there's the test criteria. For more relaxed warm waters, I think the less manufacturers make the information available.

Here's one:
Dive Rite O2ptima Rebreather Scrubber Duration Test Results | Dive Gear Express®

Too bad airways, scrubber canister materials etc effect scrubber temperature so much otherwise we could extrapolate the data for other scrubbers.

I agree we would be able to make our own adjustments based on their lab results.

Interesting topic,
Cameron
 
rEvo publish scrubber duration (for using one and both canisters) for water temps greater than 4C and 15C for Sofnolime 797 and Intersorb 812. They also publish scrubber endurance at 40 and 100m at 4C.

Of course the rEvo has the rMS scrubber monitoring system and for a typical dive in water temps of greater than 15C I get 4-4.5hrs per cycle (1.35kg of sorb) and in water temps of around 28-30C I am getting 5.5-6hrs per cycle (1.35kg of sorb) using the rMS.

I find the rMS a highly valuable tool and takes all the guess work and uncertainty out of determining scrubber duration providing you with real time information on scrubber status, thus able to make informed decisions about what to do with your scrubber for upcoming dives. Along with the rEvo unique duel scrubber system it allows you to make use of all sorb.
 
Off the top of my head, the CE test parameters call for something like 1.3L of CO2 per minute with a flow rate ("breathing rate") of between 25-40L of air in 39° water at 40m of depth. In reality, most of us aren't generating that much CO2 for the tested duration of the scrubber in that temperature of water.

Having said that, you should be relatively safe from the effects of breakthrough if you stay within the duration of your scrubber.

Given that the risks from CO2 include narcosis, blackout, heart attack, and death, I would be really hesitant to dive beyond the CE rated scrubber duration because of something I read from some random person on the internet.
 
Given that the risks from CO2 include narcosis, blackout, heart attack, and death, I would be really hesitant to dive beyond the CE rated scrubber duration because of something I read from some random person on the internet.

Absolutely agree, which is why I would prefer to have a lab generated rating with the same degree of accuracy as the CE 4°C rating to cover my actual diving conditions. So the question is - does the manufacturer only test at 4°C because the "notified body" that does conformity assessment for CE specify 4°C somewhere? Or is a single (arbitrary) temperature chosen to minimize testing costs while still ensuring CE?
 
Off the top of my head, the CE test parameters call for something like 1.3L of CO2 per minute with a flow rate ("breathing rate") of between 25-40L of air in 39° water at 40m of depth. In reality, most of us aren't generating that much CO2 for the tested duration of the scrubber in that temperature of water.

Having said that, you should be relatively safe from the effects of breakthrough if you stay within the duration of your scrubber.

Given that the risks from CO2 include narcosis, blackout, heart attack, and death, I would be really hesitant to dive beyond the CE rated scrubber duration because of something I read from some random person on the internet.

EN14143 standards are 40 m depth, 4 degrees C (39.2 F) water temperature, 40 lpm breathing rate, and 1.6 liter of CO2 generation. It's easy to remember roughly as 40 m, 40 degrees F, and 40 lpm.

The 5.7 pound KISS classic scrubber using 5.7 pounds of Sofnolime 797 gave a scrubber duration of 2 hours and 37 minutes to 5 millibar of CO2, and only slightly longer at 2 hours and 50 minutes to 10 millibar of CO2. Once a scrubber starts to break through, it goes fast. As an aside, the NATO test standard STANAG number 1411 uses a CO 2 production rate of 3 lpm, which is way over the top.

The problem with the CE based durations are two fold in that you don't get the breakthrough along the side of an axial flow scrubber canister as quickly in warm water, and no body on the planet can sustain 40 lpm ventilation rates for 2-4 hours.

That makes them very conservative - almost to the point of non usability for real world purposes, and while that's convenient from a liability standpoint, it leaves individual CCR divers as more or less their own scrubber duration test dummies with not much to go on and that's unfortunate.

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I agree with you Ken that exceeding the rated scrubber duration has it's perils, but I suspect many, if not most, CCR divers are doing that based on their personal progressive experience with their scrubber under specific conditions.

We have for example done 4 hour swimming dives on our KISS sidekicks with a similar amount of 8-12 mesh sorb in 70 degree water with a light workload (normal 50 fpm swim rate interspersed with some pulling and slower swim rates in restrictions and small passages).

That's a fair bit more than the CE duration of 2 hours 37 minutes suggests, but we've worked up to that slowly and we're always cognizant of the caveats in the form of the specific conditions that accompanied these longer duration dives.
 
I agree with you Ken that exceeding the rated scrubber duration has it's perils, but I suspect many, if not most, CCR divers are doing that based on their personal progressive experience with their scrubber under specific conditions.

See, this is exactly why I raised the question. I'm already diving a non-CE unit, as are many US divers. So it's not like the only possible standard that I could use in determining scrubber duration would be the 4° C one from EN14143 (2003 version).

Wouldn't it be better for manufacturers to somehow generate accurate duration data for other temperatures than for divers to be their own crash test dummies by using fudge factors and slowly pushing the limits? Yes, the CE conditions result in a very conservative estimate of scrubber duration given the sustained ventilation rate. And while it might seem that one is going to be injured by making the standards TOO conservative, there is a point of diminishing returns. At some point, people start pushing the limits if they feel that the standards are too far from real world conditions.
 
If you want to sell a CCR in Europe, it has to be CE certified. My understanding is the cost of getting the CE rating is fairly expensive.

If you're already spending a bunch of coin on the CE certification and testing, and that gives you a scrubber duration number that will probably be quite defensible in a legal arena, why would you pay to do additional testing?

And finally, how many people really do dives that exceed the duration of CE scrubber rating? The number of people that do dives in excess of 3.5 in duration is very small.
 
If you want to sell a CCR in Europe, it has to be CE certified. My understanding is the cost of getting the CE rating is fairly expensive.

If you're already spending a bunch of coin on the CE certification and testing, and that gives you a scrubber duration number that will probably be quite defensible in a legal arena, why would you pay to do additional testing?

And finally, how many people really do dives that exceed the duration of CE scrubber rating? The number of people that do dives in excess of 3.5 in duration is very small.

Right, but the same manufacturer can produce a non-CE version for international sales (like Meg and JJ do, and maybe others). That doesn't impair European sales, but it does give the manufacturer a sales advantage elsewhere. For example, if JJ didn't sell an international version, I would have to consider the downside of possibly not being able to rent tanks locally when I dive in the Caribbean (like I did last week), and maybe I would go with another unit. So you might pay to do additional testing if it would make your product more attractive to people who were buying non-CE rebreathers anyway (USA, Caribbean, Pacific, South America, middle east - not a small diving market). Whether or not the additional sales would pay for additional testing is a business question that I can't answer.

And for me, it's not necessarily about long dives, it's logistics and avoiding extra scrubber changes for multi dive days. Again, not looking for a safety shortcut, I'm looking for reliable data about how long the scrubber actually lasts in the relevant conditions.
 
https://www.shearwater.com/products/teric/

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