Contaminant monitoring and control is vital in maintaining a habitable atmosphere in an enclosed environment. Substances which impair normal human psychophysiological functions are constantly being produced. This requires both contaminant monitoring and removal equipment. In addition to actively removing contaminants, a passive control program can limit the types of undesirable materials allowed inside the environment.This paper will discuss potential sources of airborne contaminants, how they are monitored, and passive and active methods of contaminant control. The paper will also discuss some of the system design constraints and parameters involved in both an undersea submersible vehicle and a space based facility.