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 battery condenser systems based on the EPA-approved stack sampling methodology, Method 201A. The project plan included sampling seven cotton gins across the cotton belt. Key factors for selecting specific cotton gins included: 1) facility location (geographically diverse), 2) industry representative production capacity, 3) typical processing systems, and 4) equipped with properly designed and maintained 1D3D cyclones. Six of the seven gins were equipped with battery condensers with cyclones on the system exhausts. In terms of capacity, the six gins were typical of the industry, averaging 30.9 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 battery condenser system PM2.5 emission factor based on the six tests (15 total test runs) was 0.0037 kg/227-kg bale (0.0081 lb/500-lb bale). The battery condenser system average emission factors for PM10 and total particulate were 0.012 kg/bale (0.026 lb/bale) and 0.037 kg/bale (0.081 lb/bale), respectively. The battery condenser system PM2.5 emission rate from test averages ranged from 0.044 to 0.14 kg/h (0.10-0.30 lb/h). System average PM10 and total particulate emission factors were higher than those currently published in EPA AP-42. The ratios of battery condenser system PM2.5 to total particulate, PM2.5 to PM10, and PM10 to total particulate were 10.0, 30.9, and 32.3%, respectively.