Hi Baz, I'd guess the instructor in question is refering to an increasaed posibility of CO2 breakthrough from overbreathing more so than as a function of the duartion.

Considering that Dragersorb is 5-9 mesh-bigger than 8-12 Sofno or 6-12 Sodasorb-and that it's designed for use in an SCR, where CO2 buildup is less likely to begin with, I'd guess that in a radial with it's shorter grain boundry and lower WOB than an axial, the potential for gas passing through before it's properly scrubbed due to a high work rate is certainly possible. The Prism radial is designed for use with 6-12/8-12-bigger mesh szes are not recomended for anything other than pool training and I guess that could very well be the reason... -Andy