Effects of Varying Environmental Parameters on Trace Contaminant Concentrations in the NASA Space Station Reference Configuration

The effects of varying carbon dioxide (CO₂) and oxygen (O₂) concentrations, relative humidity, temperature, and pressure on the production and depletion of trace contaminants in the NASA Space Station Reference Configuration have been evaluated. This evaluation was conducted using a Space Station trace contaminant computer model developed specifically to predict the effects of chemical reactions and physical processes on gaseous trace contaminant concentrations as functions of time. The sensitivity of trace contaminant concentrations to changing CO₂ and O₂ concentrations, relative humidity, temperature, and pressure was determined. In addition, the effects of changing the initial concentrations of significant contaminants such as nonmethane hydrocarbons and nitrogen oxides on concentrations of other trace contaminants of importance were examined. Changing the initial concentrations of nonmethane hydrocarbons and nitrogen oxides produced more significant changes in the concentration levels of trace contaminants than did pressure and humidity variations. Oxygen and carbon dioxide changes had negligible effects on trace contaminant concentrations. Results which include implications of the analysis on the design of the Space Station trace contaminant control systems are presented.