Development of Challenge Aerosols for Testing Filters in Spacecraft Air Revitalization Systems

The common means for reducing particle concentrations in air in enclosed spaces, including in space habitats, are source prevention and particle removal by air filters. While air filtration and testing is a well-established discipline and industry, testing and classifying filters according to commonly used standards rely on a test aerosol that is often arbitrary and chosen for the convenience of the test method. In space habitats, the particle size distributions are expected to be quite different than the particle size distributions prescribed in test standards, due to the partial or low gravity environment affecting sedimentation of large particulates like hair or cloth fibers, or the introduction of planetary dust to the pressurized volume. This means that the efficacy of the filter will be quite different in the space habitat than specified according to a prevailing standard. This paper will present some initial work in development of a “composite” challenge aerosol to bound the measured and reported particle sizes reported for the International Space Station (ISS), and for expected particulate matter in a Lunar lander, habitat, or orbiting platform susceptible to the intrusion of Lunar dust. Application of this test aerosol is expected to yield filter efficiencies and loading effects closer to what one can expect on these spacecraft and be useful in determining filter lifetime and replacement cycles.