A life support system (LSS) is usually defined as a system that provides elements necessary for maintaining human life and health in the state required for performing a prescribed mission. The LSS@ depending upon specific design requirements@ will provide pressure@ temperature@ and composition of local atmosphere@ food@ and water. It may or may not collect@ dispose@ or reprocess wastes such as carbon dioxide@ water vapor@ urine@ and feces. It can be seen from the preceding definition that LSS requirements may differ widely@ depending on the mission specified@ such as operation in Earth orbit or lunar mission. In all cases the time of operation is an important design factor. An LSS is sometimes briefly defined as a system providing atmospheric control and water@ waster@ and thermal management. The major subsystems required to accomplish the general functions mentioned above are: 1. Breathing and pressurization gas storage system. 2. Temperature and humidity control system. 3. Carbon dioxide control system. 4. Trace contaminant control system. 5. Water management system. 6. Waste management system.