Attrition is very important for limestone particles used to capture SO2 and CO2. In this study, the attrition of limestone particles was investigated at room temperature using an air-jet apparatus, based on the standard ASTM D 5757-00 method. The mass percent of fines increased almost linearly with time for 125-850 mu m particles. In the attrition process, abrasion was initially the main mode of attrition for 710-850 mu m particles, causing the particles to become rounded and smooth. Fragmentation became important as well when the particles reached the 200-400 mu m range and became the main mode of attrition for particles smaller than 180 mu m. The change in the mode of attrition is important, as attrition models tend to assume that the mode is always the same. (C) 2010 Elsevier B.V. All rights reserved.