Info PSA - Rebreather CO2 Absorbent

[SavageSeaCow]

The difference between medical sorb and diving sorb is the water content. Water is an essential reactant in the conversion of CO2 (it is also a biproduct). Medical sorb has very little water in it because anesthesia machines use humidified air in the OR. This is why it can’t be used in diving where your exhaled moisture is not enough. It is not a matter of breathing rate, and shallow depth or low work load is not likely to save you if you are chancing it. Use only diving grade sorb for diving applications.

 

[tomfcrist]

The difference between medical sorb and diving sorb is the water content. Water is an essential reactant in the conversion of CO2 (it is also a biproduct). Medical sorb has very little water in it because anesthesia machines use humidified air in the OR. This is why it can’t be used in diving where your exhaled moisture is not enough. It is not a matter of breathing rate, and shallow depth or low work load is not likely to save you if you are chancing it. Use only diving grade sorb for diving applications.

Medical sorb is a 12-19% water content. Diving sorb is 15-20%.

 

[broncobowsher]

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.

Like buying oxygen? Medical grade, need a prescription from a doctor, pain to get. Welding grade, how much do you want? Difference in specs, only at the extreme limits. If you are getting oxygen that close to the limits, probably should find a new source.

 

[Cio]

. Like buying oxygen? Medical grade, need a prescription from a doctor, pain to get. Welding grade, how much do you want? Difference in specs, only at the extreme limits. If you are getting oxygen that close to the limits, probably should find a new source.

Med grade is vacuumed prior to filling so the possibility of contamination is just about nil. Welding is a dump and fill, practically no real difference but if someone misuses a Welding tank and then an operator doesn't fully dump, could be an issue. So, in that case there is a definable difference in guaranteed putity. WhaI am referencing is literally identical in every way other than label

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.

The large particle size is a clear difference and would certainly show that in performance. I don''t think l this would exclude it from use in large scrubbers where typical sized sorb creates increased WOB. Pretty simple surface area calculations could be doe to determine at what point this would be providing appropriate surface area.

 

[Cio]

The difference between medical sorb and diving sorb is the water content. Water is an essential reactant in the conversion of CO2 (it is also a biproduct). Medical sorb has very little water in it because anesthesia machines use humidified air in the OR. This is why it can’t be used in diving where your exhaled moisture is not enough. It is not a matter of breathing rate, and shallow depth or low work load is not likely to save you if you are chancing it. Use only diving grade sorb for diving applications.

After a very short time the loop is 100% RH it literally could not hold any more moisture.

 

[Puppeteer]

The large particle size is a clear difference and would certainly show that in performance. I don''t think l this would exclude it from use in large scrubbers where typical sized sorb creates increased WOB. Pretty simple surface area calculations could be doe to determine at what point this would be providing appropriate surface area.

It's more than just raw particle size. They also mention morphology. A smooth particle will have much less surface area than a crinkly particle. This can be an immense difference, more than 1000x surface area at the same particle size in some cases with particular substances. Without an in depth understanding of the morphology differences, you won't be able to estimate surface area from particle size. Be very careful attempting this.

 

[Cio]

It's more than just raw particle size. They also mention morphology. A smooth particle will have much less surface area than a crinkly particle. This can be an immense difference, more than 1000x surface area at the same particle size in some cases with particular substances. Without an in depth understanding of the morphology differences, you won't be able to estimate surface area from particle size. Be very careful attempting this.

We are still reacting with human breath to scrub co2 so, all though the theoretical surface are could be massively different, that makes no sense practically.