This report is part of a project to characterize cotton gin emissions from the standpoint of stack sampling. The impetus behind this project was the urgent need to collect additional cotton gin emissions data to address current regulatory issues. A key component of this study was focused on Environmental Protection Agency (EPA) total particulate emission factors. There is no total particulate emission factor published for 1st stage lint cleaning systems in the 1996 EPA AP-42. The current AP-42 factor represents 1st and 2nd stage lint cleaning systems combined. The objective of this study was to collect total particulate emission factor data for 1st stage lint cleaning systems from cotton gins located in regions across the cotton belt using EPA-approved stack sampling methodology. The project plan included sampling seven cotton gins. Key factors for selecting specific cotton gins included: 1) facility location, 2) production capacity, 3) processing systems, and 4) abatement technologies. Four gins with 1st stage lint cleaning system exhausts that were not combined with 2nd stage lint cleaning system exhausts were sampled. The average production rate during testing for the four gins was 25.7 bales/h. The average 1st stage lint cleaning system total particulate emission factor based on four tests (12 total test runs) was 0.070 kg/227-kg bale (0.155 lb/500-lb bale). The 1st stage lint cleaning system emission rate test averages ranged from 0.67 to 3.56 kg/h (1.49-7.84 lb/h).