I am just now starting into SH4 and am on my 4th patrol - tthe objective for this one is to patrol Honshu. What I'm finding is that the CO2 level is reaching 90% before I complete the objective or can head for Pearl or any port for that matter. My crew dies from lack of oxygen even though we have been running mainly on the surface except when avoiding aircraft or attacking targets. Is there a way to vent the CO2? It continues to build no matter how long I run on the surface.
