sprockjohnson
Contributor
I'm putting this in the Rebreather Diving section but it could also go into the accidents and near misses section. However, I think it belongs more in Rebreather Diving as it involves a question about scrubber canister design.
I have a Sport KISS and for those of you not familiar with the design it utilizes a square shaped scrubber canister which slides down into the metal case of the rebreather. There are no springs or any spring-like material used to compress scrubber material after it has been filled and you simply have to fill, tap, fill, etc. until the scrubber material is level with the bottom of the black plastic connectors on top of the scrubber which the opv/ adv pod and the sensor pod screw into. Any compression of the scrubber material occurs due to these pods sitting just below the bottom of these connectors when inserted. The openings for the filling of the scrubber are round and do not extend to the edges of the top of the scrubber canister, leaving approximately 1/2 to 1" of space around the openings to the corners.
Yesterday I did a dive at a freshwater spring and at a depth of 162' and a runtime of around 5 minutes began to experience what I'm fairly certain was hypercapnia. I was able to bailout to the necklaced regulator fed by an AL80 and ascended to about 70', after which my respiratory rate slowed down to a more normal rate. My ppo2 was a maximum of 1.00 at the bottom and after bailing out and checking again after I had calmed down it was at approximately 0.70 at the 70' depth. I attempted to go back on the loop to see if it was just a fluke and within about 30 seconds determined it was not and began to experience the same symptoms and again had to bailout to OC.
As a side note I was wearing a Garmin G2 as a backup computer and it was able to log my heartrate and showed an average of 94 bpm during the dive with a maximum of 109 bpm, which was much lower than I would have expected.
While leaving the dive site and speaking with another rebreather diver on the way out he brought up an interesting point which is where my question lies-
The square scrubber design obviously has corners. Specifically corners near the top which can be hard to verify whether they were completely filled with sodalime regardless of how much tapping is done. I checked my scrubber after the dive and after pulling the pods off the top I noticed a very small amount of unfilled space near these corners. The scrubber material just below where the pods screw into appeared to have been slightly compressed as intended. It did not appear like there were any visible channels going down from these corners which could assist in a breakthrough.
Anybody know if this was likely the reason for the CO2 retention? Is this a design flaw inherent to the square scrubber design or more likely my mistake with packing the scrubber? Just curious for the future with my unit and also wondering about the square design which appears to be incorporated in the Sidewinder 2, although that design has a spring system to compress the material.
I have a Sport KISS and for those of you not familiar with the design it utilizes a square shaped scrubber canister which slides down into the metal case of the rebreather. There are no springs or any spring-like material used to compress scrubber material after it has been filled and you simply have to fill, tap, fill, etc. until the scrubber material is level with the bottom of the black plastic connectors on top of the scrubber which the opv/ adv pod and the sensor pod screw into. Any compression of the scrubber material occurs due to these pods sitting just below the bottom of these connectors when inserted. The openings for the filling of the scrubber are round and do not extend to the edges of the top of the scrubber canister, leaving approximately 1/2 to 1" of space around the openings to the corners.
Yesterday I did a dive at a freshwater spring and at a depth of 162' and a runtime of around 5 minutes began to experience what I'm fairly certain was hypercapnia. I was able to bailout to the necklaced regulator fed by an AL80 and ascended to about 70', after which my respiratory rate slowed down to a more normal rate. My ppo2 was a maximum of 1.00 at the bottom and after bailing out and checking again after I had calmed down it was at approximately 0.70 at the 70' depth. I attempted to go back on the loop to see if it was just a fluke and within about 30 seconds determined it was not and began to experience the same symptoms and again had to bailout to OC.
As a side note I was wearing a Garmin G2 as a backup computer and it was able to log my heartrate and showed an average of 94 bpm during the dive with a maximum of 109 bpm, which was much lower than I would have expected.
While leaving the dive site and speaking with another rebreather diver on the way out he brought up an interesting point which is where my question lies-
The square scrubber design obviously has corners. Specifically corners near the top which can be hard to verify whether they were completely filled with sodalime regardless of how much tapping is done. I checked my scrubber after the dive and after pulling the pods off the top I noticed a very small amount of unfilled space near these corners. The scrubber material just below where the pods screw into appeared to have been slightly compressed as intended. It did not appear like there were any visible channels going down from these corners which could assist in a breakthrough.
Anybody know if this was likely the reason for the CO2 retention? Is this a design flaw inherent to the square scrubber design or more likely my mistake with packing the scrubber? Just curious for the future with my unit and also wondering about the square design which appears to be incorporated in the Sidewinder 2, although that design has a spring system to compress the material.
