Agricultural operations are encountering difficulties complying with current air pollution regulations for particulate matter (PM). These regulations are based on the National Ambient Air Quality Standards, which set maximum concentration limits for ambient air PM. Source sampling for compliance purposes require the use of U.S. Environmental Protection Agency (EPA) approved samplers. Ideally, these samplers would produce accurate measures of the pollutant; for instance, PM2.5 samplers would produce accurate measures of PM less than or equal to 2.5μm (true PM2.5). However, samplers are not perfect and errors are introduced due to established tolerances for sampler performance characteristics and the interaction of particle size and sampler performance characteristics. A performance evaluation of the stack sampler referenced in EPA Method CTM-039 was conducted at a commercial roller cotton gin.  EPA Methods CTM-039 and 5 were used to sample the PM emissions being emitted from the gin’s No. 1 stick machine system, the overflow, and seed-cotton carryover reclaimer system, and the feeder dust system.  Total suspended particulate (TSP), PM10, and PM2.5 concentrations were obtained according to EPA defined methodology.  A particle size analysis was conducted on the filter and wash from the Method 5 sampler.  These particle size distributions and the TSP concentrations were used to determine the true PM10 and PM2.5 concentrations for comparison with the Method CTM-039 concentrations. Based on a preliminary data analysis, the CTM-039 PM10 concentrations were similar to the true PM10 concentrations.  However, the CTM-039 PM2.5 concentrations were 5.8, 11, and 13 times greater than the true PM2.5 concentrations for the stick machine, feeder, and overflow systems, respectively.