Not sure which "article" you read, but actually both CO and CO2 are concerns in shelters. The CO concern primarily stems from fires external to the shelter - it is a safe assumption that there would be many fires raging out of control, especially if a nuke was detonated in an urban area.<br><br>The CO2 (and water vapor) concerns are from shelter occupants respiration, and these are real concerns regardless of external conditions.<br><br>So, even if the article you read has them mixed up, both are things that must be planned for and dealt with. Hope that helps.<br><br>Tom