This report is part of a project to characterize cotton gin emissions from the standpoint of stack sampling. In 2006, EPA finalized and published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created an urgent need to collect additional cotton gin emissions data to address current regulatory issues, because current EPA AP-42 cotton gin PM2.5 emission factors did not exist. The objective of this study was the development of PM2.5 emission factors for cotton gin mote cleaner systems based on the EPA-approved stack sampling methodology, Method 201A. The project plan included sampling seven cotton gins across the Cotton Belt. This information is repeated in the body of the text and this detail can be left out in the abstract shortening it some. Some test runs were excluded from the test averages because they failed to meet EPA Method 201A Test criteria. Also, other test runs, included in the analyses, had cotton lint fibers that collected in the ≤ 10 µm and/or ≤ 2.5 µm samples. This larger lint material can impact the reported emissions data, but EPA Method 201A does not suggest methods to account for these anomalies. Average measured mote cleaner system PM2.5 and total particulate emission factors for the stand-alone mote cleaner system were 0.0036 kg/227-kg bale (0.0079 lb/500-lb bale) and 0.065 kg/bale (0.14 lb/bale). The average total particulate emission factor for the stand-alone mote cleaner system was lower than those currently published in EPA AP-42 for similar systems. The ratio of mote cleaner system PM2.5 to total particulate was 5.5%. Average measured PM2.5 emission factors for the mote cleaner system combined with the module feeder dust system was 0.022 kg/bale (0.050 lb/bale).