Hello Delfi,
This is a well known problem with the game when it was developed. It normally happens when you 'ALT+Tab' to leave the game to look at something else on your computer and sometimes when your computer drops you out of the game. But there is an easy solution to fix this. First save your game, exit the program and restart. After loading the save, the co2 problem will be be fixed. If I may, I suggest reading this topic by Capn Scurry,
[TEC] Windows10; Large Address Aware; SH4 Install And of course here is another link that may help,
http://www.subsim.com/radioroom/showthread.php?t=219029 by the THEBERBSTER, which has a wealth of knowledge. Good luck and Happy Hunting!