actually, as the math works out, cannister duration has everything to do with the weight of the absorbant itself, and is independent of intergranular space (assuming that velocity, dwell time, temp, etc are all constant). The 'density' of absorbant is usually listed around .9g/cm3. HOWEVER, this is the density of a cm3 of absorbant pellets, not the solid chemical. Actual absorbant capacity is defined by the chemical weight/density, which off of the MSDS sheet is roughly 2g/cm3.
now, the scrubber's actual performance is dependent on the physical characteristics of the pellet size and shape, as this factors in to dwell time and gas velocity.
so practically speaking, 3L of sofnlime vs 3L of dragersorb are very different animals, but this is directly related to the weight of absorbant required to fill each of these spaces, and each's varying makeup (it's slight, but does have some effects)
it's actually been quite an interesting excersize to work though the precise physics mathematically and froma chemistry/physics perspective.
Quote: (Originally Posted by
nigelh)
does the 'sorb effect depend on the weight?
If I switch from Sofnoline to Dragersorb on holiday the volume is the same so I want to know if the same volume gives me more or less time so a weight number sends me off on a quest for density values and complicates matters.
If I change rebreather either will do as I want to ratio my normal usage times.
I'd go for volume. Weight is easy to measure for an experement but less useful in real life.