Candidate sorbents for air revitalization aboard the International Space Station (ISS) include impregnated activated carbons for NH3 removal and activated carbons for trace contaminant removal. A rapid method for determining the adsorptive capacities of these sorbents uses small particle size (~12x20 mesh) to allow breakthrough curves to be determined in 8-12 hours, as opposed to 3-4 days for conventional 4x8 particles. In this study, the effect of particle size on the measurement of adsorptive capacity measurements is determined by comparing capacities obtained using crushed vs uncrushed sorbents exposed to the same simulated spacecraft gas streams. The effect of particle size was studied using activated carbons and acid impregnated activated carbons.