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Guidelines for Developing Spacecraft Maximum Allowable Concentrations for Space Station Contaminants (1992) / Chapter Skim
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'ENVIRONMENTAL CONTROL AND LIFE-SUPPORT SYSTEM'
Pages 41-48

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
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From page 41...
... Air temperature and humidity are controlled by a condensing heat exchanger with automatically controlled bypasses in each node and module of the station. From a central location, the THC subsystem manages intermodule ventilation, air exchange between pressured elements of the station to maintain the proper total pressure and O2 and CO2 partial pressures.
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From page 42...
... . The ARS is designed to maintain exposures below the 180-day SMACs for normal rates of contaminant generation when the station is "permanently manned," and below the 30-day SMACs when the station is only "man-tended." In addition, means are being devised to reduce contaminant levels following unanticipated releases to meet the 1 - and 24-hr SMACs, but these additional safety measures are not part of the baseline design.
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From page 43...
... co £ B | CO CO c O I1 CD i c i ^ X T3 0)
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From page 44...
... Good design practices for laboratories on earth usually include restricting air flow from the laboratory to adjoining nonlaboratory spaces by keeping the laboratory under negative pressure with respect to those adjoining spaces. On the space station, however, air will be flowing, by design, from the laboratory module to adjacent nodes to maintain CO2 levels and temperature and humidity control.
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From page 45...
... It is not recommended for complete recirculation because the ARS will remove chlorofluorocarbons only very slowly and may generate more toxic airborne contaminants. The subcommittee is concerned also that some products generated by fires and by chemical fire extinguishers could rapidly and severely compromise performance and impair the health of the astronauts.
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From page 46...
... Nevertheless, the cabin air condensate is expected to contain numerous volatile organic compounds that are either present as vapor in the return air stream or vaporize from particulate material collected on the filters. Condensate from space-shuttle missions has been shown to contain a wide variety of organic contaminants.
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From page 47...
... In addition, the use of the model in this manner would help identify gaps in the current understanding of system performance. The overall plan for monitoring air contaminants, biological monitoring of the crew, and complying with the SMAC values should be developed by a team including industrial hygienists, physicians, toxicologists, behavioral toxicologists, and health physicists, as well as chemists and engineers.
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Key Terms

  • environmental control
  • cabin air
  • contaminant control
  • contaminants removed
  • biological monitoring

  • catalytic oxidizer
  • laboratory modules
  • air monitoring
  • air exchange
  • air stream

  • air changes
  • air temperature
  • cabin atmosphere
  • acutely toxic
  • volatile organic

  • trace contaminants
  • laboratory module
  • accidental release
  • response procedures
  • condensing heat

  • thc subsystem
  • reasonably probable
  • heat exchanger
  • flow rate
  • humidity control

  • air condensate
  • periodic air
  • restricting air
  • air cooling
  • return air


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