How long can you expose a scrubber to air?

[Mobulai]

Not sure why people keep bringing this topic up over and over

Given the popular demand for more info and tests and data about this cluster of topics (reusing sorb); I’m opening up donations to build a SNORT machine

I was already planing to build one for a few months (almost a year actually), but it’s a pricey endeavor and each test run costs so I’m still saving for it; I’m open to running all sorts of test variations (to those interested and willing to supplement the consumables costs)
You wanna try the impact of repacking sorb? Sure; adding sawdust to it, why not — let’s get these questions answered once and for all
(Not sarcasm)

Personally the most Id do is reuse yesterdives sorb if both last and next dives are less than 90mins — in hot dry environment like Dahab; and the snort is intended for canister design verification (someday I wish to make my own)
But resources can be managed well by sharing

Whoever is intrigued and feels generous just write me

 

[inquis]

Sorb is constantly “degrading” if you think about it. Whether it’s in a dry unit, moist unit, or the tub.

"Constantly degrading" seems rather inaccurate. In the tub (once recapped), after the CO2 is converted, it stops degrading -- the reactants are no longer present. A closed canister is no different as it is also sealed (just with a bit more volume).

 

[Dave Whitlow]

No offense but these questions about leaving scrubber packed and leaving in unit for how long are kind of dumb. It’s like asking how long will it take for my Hershey’s bar to melt in the sun. There’s so many variables there is no way to actually study it and get a universal answer that correlates to conditions outside of the study conditions.
Think about it. As soon as you open a tub of sorb it’s exposed to air. It’s not like sorb lives in some magical vessel that keeps it fresh. Sorb is constantly “degrading” if you think about it. Whether it’s in a dry unit, moist unit, or the tub.
Not sure why people keep bringing this topic up over and over

Much of what you said is incorrect, and people probably keep bringing this up because they hear such statements and intuitably know it is wrong, so they seek better advice. Hershey bars are horrid anyway, and an awful example of something that can be pleasant!

Sofnolime is a stable chemical and, without environment changes, remains unchanged for years. That is how chemistry works, and the whole manufacture and distribution of Sofnolime relies on this stability. In a sealed environent there a few variables and, unlike oxygen sensors, Sofnolime does not degrade with the passage of time.

The chemicals in Sofnolime function in a high moisture environment because they rely on surface moisture to absorb CO2 and enable reaction to occur, and to remove CO2. If the lime is too dry this may not work as well, so keeping it moist is good. If the scubber is sealed then the moisture and surrounding gases reach an equilibrium and, without change, this is equilibrium is maintained for some time.

The tests in the paper showed this situation persisted for weeks. I have used an undistrubed scrubber from months ago and seen it behave the same as one from a few days ago.

 

[mr_v]

The findings of that report are what one would "expect"; leave it out for 28 days and the scrubber looses its effectiveness.


My normal process is to remove the two scrubbers from the Revo and leave them to dry for a couple or few hours, then put them in a sealed Tupperware plastic container (one per scrubber). If the dive was more than 2 hours or deep, one scrubber would be emptied, refilled and sealed in the container if the unit isn't rebuilt.

Not sure why you'd want to leave scrubbers to dry out and then put them into air tight containers. It is not necessary. If your sorb has that much moisture it is probably overused or flooded, so you need to discard it. Otherwise, you can put the scrubbers in sealed containers, trash bags, etc.

 

[mr_v]

"Constantly degrading" seems rather inaccurate. In the tub (once recapped), after the CO2 is converted, it stops degrading -- the reactants are no longer present. A closed canister is no different as it is also sealed (just with a bit more volume).

Yes, it is inaccurate. I am not sure why people say, as properly stored sorb is not like a battery that continues to degrade. You'd typically store chemicals, like the ones found in sorb, in airtight containers to prevent unnecessary reactions (preserve normality).

 

[rddvet]

"Constantly degrading" seems rather inaccurate. In the tub (once recapped), after the CO2 is converted, it stops degrading -- the reactants are no longer present. A closed canister is no different as it is also sealed (just with a bit more volume).

I was simplifying it by saying constantly degrading, which is why it was in quotes. You are correct that once the CO2 introduced into the tub is gone the reaction stops, but there is degradation everytime you open the tub because of it. Tubs are also not truly airtight. The issue is people really think that sorb is magically going to stay unaffected by the environment in its tub when you open it (regardless of how much or little that may be). Just like people seem to think sorb magically stops working after the expiration date. My main point is there is no way we're going to get a study that can take into account how long you can store a packed scrubber that can then be directly and clearly extrapolated to every environment. I guarantee you that sorb degradation in my hot, humid florida garage in a scrubber sitting on a bench will be affected differently than in the same place in a low humidity and heat environment. The point is we will only really be able to guess.

Much of what you said is incorrect, and people probably keep bringing this up because they hear such statements and intuitably know it is wrong, so they seek better advice. Hershey bars are horrid anyway, and an awful example of something that can be pleasant!

Sofnolime is a stable chemical and, without environment changes, remains unchanged for years. That is how chemistry works, and the whole manufacture and distribution of Sofnolime relies on this stability. In a sealed environent there a few variables and, unlike oxygen sensors, Sofnolime does not degrade with the passage of time.

The chemicals in Sofnolime function in a high moisture environment because they rely on surface moisture to absorb CO2 and enable reaction to occur, and to remove CO2. If the lime is too dry this may not work as well, so keeping it moist is good. If the scubber is sealed then the moisture and surrounding gases reach an equilibrium and, without change, this is equilibrium is maintained for some time.

The tests in the paper showed this situation persisted for weeks. I have used an undistrubed scrubber from months ago and seen it behave the same as one from a few days ago.

You're welcome to disagree with me, but I'm not incorrect. I'm speaking from both a ccr diver and someone with advanced training in anesthesiology who deals with a multitude of similar CO2 absorbents on a regular basis. My job very much depends on having knowledge in relation to how scrubbing agents work. Yes, sofnolime is stable. The point I was making is when you open the tub, humidity and air enter and does have some effect on the sorb. It may be miniscule and irrelevant but it is a fact. But the point is, leaving sorb out in a packed container can lead to degradation as well, but for us to know to what level that degradation occurs is impossible to know because there are too many variables. As I said above, a humid, hot environment will have a different affect than sitting sorb out in a cool, nonhumid environment.
Maybe I shouldn't have used so much hyperbole, but my main point is people want clear cut answers as to how long they can sit sorb in a cannister or how safe is it to do it. I can say that I dive lightly used sorb weeks after last use depending on what that first dive entailed, and I'm confident it's safe. Will I ever see a study that tells everyone how long their sorb will stay good sitting in the cannister? No. Because there are too many variables effecting it. At best we can use some of the studies that have been mentioned and extrapolate.
But at the end of the day I see these questions pop up here and in other places and very typically the people asking are just asking for proof they can leave their scrubber packed for X period of time or they can do X length of dive and then reuse their scrubber. Most of them want a hard answer they can hang their hat on. We will likely never have an exact answer. That person has to make a judgment call based on their personal comfort levels and experience. That was my point. But I'm sure we'll keep seeing these same questions asked ad nauseum every month or two in perpetuity.

 

[rddvet]

The topic frequently pops up in my group. I am surprised it is a concern. If you have a rebreather, do the following after each dive:

- Dry the canister. You can use moisture absorbers like Shamwow and fans to speed up the process.
- Put the scrubber back into the canister.
- Put the head/lid on the canister.

Problem solved.

I do similar, but I throw them in a vacuum sealer bag that I do lightly, but not fully vaccuum before sealing

 

[lostsheep]

Not sure why people keep bringing this topic up over and over

Newer CCR divers have no way of intrinsically knowing this stuff, it’s a legitimate question. Should it be brought up in class? Probably so but that doesn’t mean one shouldn’t ask questions later.

Forums are dying as other social media takes over; forum etiquette of search before posting is dying with it.

If we want to prevent the death of this forum we should probably relax the aforementioned etiquette.

If you don’t like the question, move along.

I had a discussion with a CCR diver, we were talking about a non closed scrubber. How long are you allowed to leave it like this?

Theory: air contains CO2, sofnolime absorbs CO2, sofnolime looses capacity. But how much is this effect? Can you measure it?

Is there a scientific approach?

I have it in my head that the scrubber gains mass as it absorbs co2. With a sufficiently precise scale and if you could control other environmental factors, I suspect you could get useful data.

As always I reserve the right to be FOS

 

[rddvet]

Newer CCR divers have no way of intrinsically knowing this stuff, it’s a legitimate question. Should it be brought up in class? Probably so but that doesn’t mean one shouldn’t ask questions later.

Forums are dying as other social media takes over; forum etiquette of search before posting is dying with it.

If we want to prevent the death of this forum we should probably relax the aforementioned etiquette.

If you don’t like the question, move along.




I have it in my head that the scrubber gains mass as it absorbs co2. With a sufficiently precise scale and if you could control other environmental factors, I suspect you could get useful data.

As always I reserve the right to be FOS

More people need to learn to search.

You are correct. Weighing sorb canisters in medical settings is one of the ways use and residual use can be determined

 

[Snusmumrik]

I have it in my head that the scrubber gains mass as it absorbs co2. With a sufficiently precise scale and if you could control other environmental factors, I suspect you could get useful data.

Ah, man. ~+196,35 grams per 100 liters of absorbed CO2. But also, plenty of water due to nature of chemical reaction. For me it's too complicated.