Are you sure it's to do with pressure? I thought Carbon Dioxide was deadly in high concentrations (rather than pressures) because it prevents adequate diffusion of oxygen from and carbon dioxide into the blood stream. Deadly at about 4%.
You are totally right about CO2 being poisonous earlier than I thought, after some looking it looks like the difference is about split between what we each thought. Symptoms start setting in at a bit before 3%, and progress in seriousness, at 8% loss of consciousness is imminent.
Pretty much all gases work off of partial pressure as far as their affects on... well, really anything. The 10% to 30% Oxygen thing in this game isn't realistic. The Apollo and Mercury astronauts were perfectly fine with 100% oxygen, because the pressure was low enough that the partial pressures were about right. Likewise I remember that during Apollo 13 the CO2 got to around 13%, which would have killed them at 1 atm, but they were alright at the .5 atm of the Apollo. For a chart showing the acceptable region oxygen percentiles at various pressures, and examples of where different spacecraft/stations fell you can go here:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080032549_2008032394.pdfThe picture is on page 4 of the report, which is page 12 of the PDF. Note that that green line denoting "perfect conditions" follows almost exactly along the ".22 atm partial pressure oxygen" line.