Agricultural operations across the United States are encountering difficulties in complying with the current air pollution regulations for particulate matter (PM). Cotton gins are most frequently regulated based on results obtained from dispersion modeling that utilize emission factors from EPA’s 1996 AP-42 or emission factors derived from source sampling. PM₁₀ emission factors are typically determined from source sampling based on EPA’s Method 201a sampling protocol. Method 201a utilizes a cyclone in the sampling system to remove the larger particles and allow the smaller particles to penetrate to the filter. EPA has documented the performance characteristics of the cyclones used in Method 201a, which are similar to the performance characteristics of an ambient PM₁₀ sampler. Recent research has shown that ambient PM₁₀ samplers can over-estimate the true PM₁₀ in the ambient air when the sampler is exposed to dust with a mass median diameter larger than 10 μm. The purpose of this manuscript is to explore the potential impacts associated with determining PM₁₀ emission values for cotton gin exhausts using the EPA’s Method 201a. Two theoretical methods were introduced to estimate the true PM₁₀ emitted from the 10 process streams associated with a standard cotton gin. Estimates from the first and second methods showed that the true PM₁₀ was about 38 and 63% lower than that obtain by PM₁₀ source sampling. This corresponds to estimates of the true PM₁₀ percent of 28 and 24% for methods 1 and 2, respectively. Whereas the current estimate of the true PM₁₀ percent is 39%, as defined in EPA’s 1996 AP-42. Therefore, when cotton gins are regulated based on PM₁₀ emission factors from AP-42 or emission factors derived from source sampling based on EPA’s Method 201a they are being force to comply with more stringent PM regulations than urban type sources. The bottom line is that regulatory agencies are using sampling methods developed to regulate urban sources to regulate agricultural sources, and these methods introduce substantial errors when the mass median diameter of the dust being emitted is larger than 10 µm.