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The maintenance of the cabin atmosphere aboard spacecraft is critical not only to its habitability but also to its function. Ideally, air quality can be maintained by striking a proper balance between the generation and removal of contaminants. ...Typically, maintaining a clean cabin environment on board crewed spacecraft and space habitats is a central function of the environmental control and life support (ECLS) system.

Achieving this balance is paramount to a spacecraft's ability to sustain human life and maintain functionality. Spacecraft cabin atmosphere can best be described as an equilibrium. ...The maintenance of cabin air-quality aboard spacecraft requires a proper balance of contamination generation and removal, and environmental monitoring.

Several designs were pressure tested and found to withstand more than 3 atmospheres well in excess of typical spacecraft water or wastewater system pressures. The vessel's ability to be hard-filled permits unattended sample collection.

The Volatile Organic Analyzer (VOA) provided valuable data on the gaseous trace contaminants in the atmosphere of the International Space Station (ISS) from January 2002 through May 2003. The VOA has two analytical channels that provide redundancy, but fuse failures caused the loss of one channel in January 2003 and the remaining channel in May 2003. In early 2005 on-orbit diagnostics verified failed fuses, and in December 2005 the fuses were replaced during an inflight maintenance (IFM) session. The VOA has provided data on the ISS atmosphere since it was reactivated in 2005. This paper summarizes the IFM procedures and presents the on-orbit data from 2006 that were used to revalidate the VOA.

During the twelve month period comprising Expeditions 10 and 11, the chemical quality of the potable water onboard the International Space Station (ISS) was verified through the return and ground analysis of water samples. The two-man Expedition 10 crew relied solely on Russian-provided ground water and reclaimed cabin humidity condensate as their sources of potable water. Collection of archival water samples with U.S. hardware has remained extremely restricted since the Columbia tragedy because of very limited return volume on Russian Soyuz vehicles. As a result only two such samples were collected during Expedition 10 and returned on Soyuz 9. The average return sample volume was only 250 milliliters, which limited the breadth of chemical analysis that could be performed. Despite the Space Shuttle vehicle returning to flight in July 2005, only two potable water samples were collected with U.S. hardware during Expedition 11 and returned on Shuttle flight STS-114 (LF1).

The management of off-nominal situations on-board the International Space Station (ISS) is crucial to its continuous operation. Off-nominal situations can arise from virtually any aspect of ISS operations. One situation of particular concern is the inadvertent release of a chemical into the ISS atmosphere. In sufficient quantities, a chemical release can render the ISS uninhabitable regardless of the chemical's toxicity as a result of its effect on the hardware used to maintain the environment. This is certainly true with system chemicals which are integral components to the function and purpose of the system. Safeguards, such as design for minimum risk, multiple containment, hazard assessments, rigorous safety reviews, and others, are in place to minimize the probability of a chemical release to the ISS environment thereby allowing the benefits of system chemicals to outweigh the risks associated with them. The thermal control system is an example of such a system.

Approximately 50% of the water consumed by International Space Station crewmembers is water recovered from cabin humidity condensate. Condensing heat exchangers in the Russian Service Module (SM) and the United States On-Orbit Segment (USOS) are used to control cabin humidity levels. In the SM, humidity condensate flows directly from the heat exchanger to a water recovery system. In the USOS, a metal bellows tank located in the US Laboratory Module (LAB) collects and stores condensate, which is periodically off-loaded in about 20-liter batches to Contingency Water Containers (CWCs). The CWCs can then be transferred to the SM and connected to a Condensate Feed Unit that pumps the condensate from the CWCs into the water recovery system for processing. Samples of the condensate in the tank are collected during the off-loads and returned to Earth for analyses.