Jon, I concur, I am not sure how low a dry air purge would
drop the RH in my boat. It would be easy to test in my shop.
I have used shop air to purge my boat to drop the CO2 level
back to normal air levels but my shop air is not dry. A scuba
tank would work.
I saw a comment in the "Design guidelines for Carbon
Dioxide Scurubbers" by Nuckkas et.al., (ncsc TECHMAN
4110-1-83) that said "As a general rule, moisture levels of
the incoming gas stream should be maintained above 70 percent
RH when using SodaSorb or Baralyme." They site a reference a
US Navy report. I am not sure how hard and fast this is or
how much degradation of the scrubber occurs at lower RH's.