Monitoring atmosphere and water for content of essential and trace gases onboard the ISS and in future missions (a review)

Monitoring atmosphere inside a spacecraft is required to assure the safety of its crew. Required for sustaining human life inside a spacecraft are certain levels of oxygen and moisture content in the air, concentrations of toxic (harmful) contaminants and trace contaminants that are kept below certain threshold levels, consumption of water of the required quality in quantities that are sufficient for meeting physiological needs. Trace contaminants released into the spacecraft cabin atmosphere are generated as a result of both machinery operation and human metabolism. Depending on concentration and duration of exposure, the same toxic substance may cause various levels of human body disfunction ranging from headaches and irritation of certain organs to their lesion and impairment of physiological functions of the body. The paper discusses both existing and prospective future analyzers for determining concentrations of major and emergency gases, as well as of toxic trace contaminants, in both air and water onboard spacecraft.