Developing a Spacecraft Air Quality Index for Future Missions

Commercial space transportation must address air quality on flights in the same way that the commercial aircraft transportation industry has worked to ensure a standard of air cleanliness and breathability. There are multiple scenarios for future space transportation, ranging from multiyear exploration missions to suborbital flights on the order of minutes, and space tourism excursions with durations somewhere in-between these extremes. Written air quality standards do not exist for these scenarios at this time, but they will differ based on the mission duration and the level of life support equipment within the space vehicle. Once standards are written and implemented, the quantitative assessment of air quality must be communicated to the crew, without requiring interpretation and active management of this information. A tool to summarize pollution levels for spaceflight participants and crew members is of high importance. The most common approach for characterizing air pollution is the air quality index (AQI). The AQI system has been developed in different countries around the world, mainly for outdoor environments, based on the results of risk assessments, epidemiological studies, and current local air pollution standards. Earth-based AQIs cannot be extrapolated to microgravity indoor environments, so the objective of this work was to explore what will be required to formulate a space air quality index for future commercial spacecraft.