KISS Announces Results of Scrubber Duration Testing

Yes Joe. I don't know why the EU use the 20M depth, the 18M depth for the Prism unmanned testing was specified by USN. The unit was tested at multiple depths, both manned and unmanned and the results have not been released yet. Maybe Alex can clarify why 20M was chosen by the EU. Maybe it's an average depth of a typical recreational profile? I don't know. Would testing a scrubber with a continuous flow at an average depth be a good way to evaluate it and make planning your dives around this time simpler? Maybe, but again, I don't know if averages are an accurate way to plan scrubber life on a multi level dive.

I think useful testing could be of 3 kinds:

1) Unmanned coldwater testing of common profiles for CCR like say, a 70M dive with a 30 minute bottom time at a moderately high workload and of course the deco stops that come with them.

2) A sort of sprint test to see just how high the CO2 flow would have to be to bypass the scrubber at the beginning, middle and end of a given scrubber's life, like Stefan suggested.

Or 3) Just test every 10M depth down to 150M in cold water at a moderately high workrate unitl breakthrough and maybe these data could be put into dive planning software like any other element of dive planning-deco obligations, O2 exposure, gas consumption, etc.

It would be nice to have limits we could use in real world diving, instead of worst case scenerios. Doesn't seem like so much to ask for...

I do know that CE testing is EXTREMELY EXPENSIVE and time consuming. For accurate comparative results, ALL units need to be tested in the exact methods, standards, following the correct protocol. But to do this, one would have to own a new model of each rebreather and the $50,000 to conduct these tests.

I don’t think every rebreather manufacturer will show up with $10,000 each; at a test site on a Saturday, and over tea and cookies conduct these tests while holding hands and singing cum-bi-ya.

Even though CE test might only be completed at a specific depth by a machine that can maintain a breathing rate no human could ever hope to maintain, the ending result of any test is to collect comparative data.

It would be impossible to collect such comparison data using a human because the parameters could not be stringently maintained. In other words, a human might not maintain the exact work of breathing every minute on each rebreather making the comparative results incomplete and inaccurate.

The duration times of the test are not set up as a standard for human usage. They are set up as a comparison data between different models at specified depths so that data can be collected and compared.

I have not yet heard a good explanation why CE test criteria-or USN for that matter-are the way they are. Why are the tests conducted at 4.5C and at unsustainably high CO2 production rates? I could imagine that those who pick these conditions just want to err on the safe side. But is it really necessary to go to those extremes in lieu of a more varied testing regimen to reflect a variety of dive conditions? As somebody who travels for all my diving, often to remote tropical places, if I followed scrubber durations for cold water and super high RMV, I would not have taken most of those trips as the logistics of getting enough sorb there would have been prohibitive.

What if all speed limits were based on driving conditions on icey roads, even in places where it never snows? Would we expect those who live in Belize to obey speed limits based on the conditions in Norway?

I'm not trying to be difficult, I just want to understand why the testing is done the way it's done. -Andy

Have you seen how they drive in Norway?

Its a worst case test... if you tested it and proved a CK scrubber was good for 5hours assuming people have good dives then everyone would use them to 5hours even those people in 4.5degrees breathing hard.... then they'd be up poop creek because the can in only good for 2hrs 50min.

I think people have seen what scrubbers can do with the Vision Temp stick, its validated that in some circumstances you can push things, these tests put another mark in the sand- the one you shouldn't push.

You weigh 90kilos and never fall when you climb- which rope do you buy?
The 90kilo max, ultralight no fall one or
the 150kilo max, fall all you like model?

I know where you coming from, a chart listing scrubber times for 10, 20, 30, 40, 50, 60 etc mtrs at different tempratures assuming a set deco profile would be very nice, I think only AP have pockets deep enough for that so as things stand is probably how they'll stay?

I'm surprised at some of the replys here not imagining how this 40mtr test at huge breathing and CO2 rates relates to a 70mtr dive? 20-30minutes of effort and them an hour hanging around doing nothing.... on average a less demanding circumstance than the test. So even though the test is just a fixed point against other tests you can interpret many things from the results.

It would be impossible to collect such comparison data using a human because the parameters could not be stringently maintained. In other words, a human might not maintain the exact work of breathing every minute on each rebreather making the comparative results incomplete and inaccurate.

but it's not Moses coming down Mt Sinai.

I'm surprised at some of the replys here not imagining how this 40mtr test at huge breathing and CO2 rates relates to a 70mtr dive? 20-30minutes of effort and them an hour hanging around doing nothing.... on average a less demanding circumstance than the test. So even though the test is just a fixed point against other tests you can interpret many things from the results.


I think Jetsam are to be applauded for doing and publishing these tests, they certainly didn't need to do it to sell units!