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 cotton gin emissions data to address current regulatory issues. A key component of this study was focused on EPA emission factors for particulate matter with a particle diameter nominally less than or equal to 10 µm (PM10). The 1996 EPA AP-42 emission factors were assigned quality ratings, from A (Excellent) to E (Poor), to assess the quality of the data being referenced. Emission factor quality ratings for cotton gins were extremely low. Also, some commonly used cotton gin systems were not represented or were combined with another system under a single emission factor in AP-42. There were no 1996 EPA AP-42 emission factors published for mote cleaner systems. The objective of this study was to collect PM10 emission factor data for mote cleaner systems at cotton gins located in regions across the cotton belt based on 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, 2) production capacity, 3) processing systems, and 4) abatement technologies. Two of the seven gins had mote cleaner systems. The exhaust from one of the mote cleaner systems was combined with the module feeder dust system. The ginning rate of the two gins averaged 36.0 and 46.2 bales/h during testing for the stand-alone mote cleaner system and mote cleaner and module feeder dust system, respectively. 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 samples. This larger lint material can affect the reported emissions data, but EPA Method 201A does not suggest methods to account for these anomalies. The average measured PM10 and total particulate emission factors for the stand-alone mote cleaner system were 0.050 kg/227-kg bale (0.109 lb/500-lb bale) and 0.090 kg/bale (0.199 lb/bale), respectively. The ratio of mote cleaner system PM10 to total particulate was 54.9%. The PM10 emission rate averaged 1.79 kg/h (3.95 lb/h) for the stand-alone mote cleaner system. The average measured PM10 and total particulate emission factors for the mote cleaner system combined with the module feeder dust system were 0.071 kg/bale (0.157 lb/bale) and 0.109 kg/bale (0.241 lb/bale), respectively. The ratio of PM10 to total particulate for the mote cleaner system combined with the module feeder dust system was 65.1%. The PM10 emission rate averaged 3.27 kg/h (7.21 lb/h) for the combined mote cleaner and module feeder dust system.