Info PSA - Rebreather CO2 Absorbent

[Dsix36]

PSA - Rebreather CO2 Absorbent

Divinng grade and medical grade are two different types of CO2 absorbent and they are not interchangeable. Diving grade is designed for the breathing rate of a working (swimming) diver while medical grade is designed for the much slower breathing rate of an unconscience patient. Although the medical grade is cheaper and the price seems appealing to rebreather divers, it is a very dangerous risk and can lead to serious issues and even death. I have personal experience with using medical grade early on in my rebreather days and suffice it to say that the risk is definitely not worth the little bit of money I saved. If you have never experienced a CO2 hit, you really do not want to. If you have experienced one and managed to survive it, you are one of the people that will do anything to prevent it from happening again.

Recently NetDoc posted some CO2 absorbent for sale on behalf of another person, that on the surface would indicate it was diver grade while in fact it was medical grade. It is clearly labeled as medical grade, is color indicating, very large grain and if you purchased some (like I foolishly did) please be aware of the limitations and risks that you are about to take. If you use it on any kind of deep dive or if you ever happen to exert yourself and raise your breathing rate, then you very easily could end up in the downward spiral of a CO2 hit that usually ends in death.

This is not all gloom and doom though. If you are very careful and dive shallow and swim slow, then you wil probably be just fine. This is a risk vs. reward decision that you will have to make for yourself.

 

[happy-diver]

Well you don't always stay shallow, and in the ocean with our mates
surge and swell, swimming slow without exertion can be impossible

With some of the unwary purchasers maybe unwilling to make a fuss
It behoves netdoc and his mate to make good, and return all monies

Certainly when I'm on the sorb hunt I only buy from people of repute

 

[greeniguana]

DGX put sofnolime's memo regarding this topic on their website:

https://www.divegearexpress.com/amfile/file/download/file/193

 

[Marie13]

Glad I changed my mind and didn’t buy any.

 

[rddvet]

Glad I changed my mind and didn’t buy any.

I don't buy from people I don't know. I honestly probably won't do any bulk buys with friends unless I'm in charge of it. I bought 1/3 of a pallet with some acquaintances (people I like but don't talk to regularly enough to consider good friends). Sorb arrived, looked fine. It was dive grade, but it was color indicating and I didn't notice at first. Color indicating is annoying because if you leave it in the scrubber too long and theres humidity it can stain things blue. More of an annoyance than a problem like medical grade. But after dropping all that money you want your order to be right. A couple of the other dudes had already started diving theres weeks before me. They never told me it was color indicating (and it made me question whether that was intentionally left out) and since they'd already used some its not like we could send it back. Even with none being used, its not worth the cost to ship back.
So I agree with Don, buyer beware. Even acquaintances will screw you either intentionally or inadvertantly.
Subgravity is usually the best price around due to free shipping.

 

[berndo]

It was dive grade, ...

Does it actually say dive grade on the keg? On the sofnolime kegs I have it just says 797 grade and 1.0 - 2.5 mm, it doesn't say medical or dive grade anywhere on the label.

 

[Marie13]

I don't buy from people I don't know. I honestly probably won't do any bulk buys with friends unless I'm in charge of it. I bought 1/3 of a pallet with some acquaintances (people I like but don't talk to regularly enough to consider good friends). Sorb arrived, looked fine. It was dive grade, but it was color indicating and I didn't notice at first. Color indicating is annoying because if you leave it in the scrubber too long and theres humidity it can stain things blue. More of an annoyance than a problem like medical grade. But after dropping all that money you want your order to be right. A couple of the other dudes had already started diving theres weeks before me. They never told me it was color indicating (and it made me question whether that was intentionally left out) and since they'd already used some its not like we could send it back. Even with none being used, its not worth the cost to ship back.
So I agree with Don, buyer beware. Even acquaintances will screw you either intentionally or inadvertantly.
Subgravity is usually the best price around due to free shipping.

I knew Mike Fisch (the deceased SB member who had the sorb). I stayed with him at his invite when I was in FL in late 2021. He brought the sorb from Europe when he moved over. So not an unknown seller for me.

 

[berndo]

It is clearly labeled as medical grade, is color indicating, very large grain and if you purchased some (like I foolishly did) please be aware of the limitations and risks that you are about to take.

I'm not claiming I know anything about this because I don't, but the grain size seems to be the same and not larger as you say. It's 797 grade 1.0-2.5 mm on the stuff you're supposed to use in a JJ and it's also 797 grade 1.0-2.5 mm in the kegs that were posted in the other thread.

I never met Mike, but I know he had been diving (tx/cave) and running a filling station for a 100 years in southern Germany and was a fairly well known guy. I'd be surprised if had been buying stuff you can't or should not use for deep diving.

Again I wouldn't know from experience, and maybe somebody else can chime in here but it's seems it's the same stuff you'd put in a JJ apart form the colour indication.

Edit: The pdf from DGX seems to be from 2010. Not sure if that make any difference, just saying.

 

[Cio]

I only offer this as contrast and since I have plenty of experience with chemicals. For reference, I think EACs are the ****, best sorb. ( period) you want reliability, dive those.

So, before this sorb is hung out to dry. Understand that, everything chemical related is called something different for every single purpose, there are chemicals, all the same, sold under 100 different names for varying purposes. Say the wrong thing to a sales rep and you can’t have that ryg13r cause it isn’t for washing clothes. The same thing is packaged and sold under brightFacto90 and if you ask, a 5 gallon pale will show up in a week ( or so). There are products you need a license to buy if you purchasethe under name x for a purpose y, and nothing if purchased under name a for purpose b.

What is the difference? Does anyone know? I’ve talked with @Dsix36 before and, no doubt, he is a more experienced diver than me, so not trying to step on a toe here but do we know the functional difference? If not, let’s peel this onion.

 

[Puppeteer]

I only offer this as contrast and since I have plenty of experience with chemicals. For reference, I think EACs are the ****, best sorb. ( period) you want reliability, dive those.

So, before this sorb is hung out to dry. Understand that, everything chemical related is called something different for every single purpose, there are chemicals, all the same, sold under 100 different names for varying purposes. Say the wrong thing to a sales rep and you can’t have that ryg13r cause it isn’t for washing clothes. The same thing is packaged and sold under brightFacto90 and if you ask, a 5 gallon pale will show up in a week ( or so). There are products you need a license to buy if you purchasethe under name x for a purpose y, and nothing if purchased under name a for purpose b.

What is the difference? Does anyone know? I’ve talked with @Dsix36 before and, no doubt, he is a more experienced diver than me, so not trying to step on a toe here but do we know the functional difference? If not, let’s peel this onion.

I'm a chemist but don't have any expertise with Sorb. Reading through the pdf linked above and from my knowledge of gas exchange one of the differences between medical grade and diving grade in this instance appears to be particle size and particle morphology. This is almost certainly to provide a much larger surface area on the sorb for the more rigorous demands of diving. The gas exchange occurs on the surface of solids (like the surface of our lungs), so having a large surface area (eg from finer particle size) would result in much faster gas exchange, but this would be at the expense of harder work of breathing.

I think opting for a larger particle size optimized for reduced pressure drop would be extremely unwise in this application.