This report is part of a project to characterize cotton gin emissions from the standpoint of stack sampling. In 2006, the Environmental Protection Agency (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 combined mote systems based on the EPA-approved stack sampling methodology, Method 201A. The project plan included sampling seven cotton gins across the Cotton Belt. Two of the seven gins had first and second-stage mote systems where the exhaust airstreams were combined. In terms of capacity, the two gins were typical of the industry, averaging 35.1 bales/h during testing. 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 combined mote system PM2.5 emission factor based on the two tests (six total test runs) was 0.0095 kg/227-kg bale (0.021 lb/500-lb bale). The combined mote system emission factors for PM10 and total particulate were 0.137 kg/bale (0.301 lb/bale) and 0.141 kg/bale (0.311 lb/bale), respectively. The combined mote system PM2.5 emission rate from test averages ranged from 0.21 to 0.45 kg/h (0.47-0.99 lb/h). System average PM10 and total particulate emission factors were higher than those currently published in EPA AP-42. The ratios of combined mote system PM2.5 to total particulate, PM2.5 to PM10, and PM10 to total particulate were 6.7, 7.0, and 96.7%, respectively.