The report describes efforts to relate coal and fly ash properties to the fabric filter specific resistance coefficient, K sub 2, and to extend the GCA/EPA fabric filter model to include pulse-jet filter theory. Fly ashes from coal produced in various parts of the U.S., including low sulfur western coals, were examined for physical and chemical properties that might correlate with the magnitude of the K sub 2 parameter. Variation in K sub 2 between fly ashes has been noted, but its specific causes have not been delineated. Results of this work showed a strong correlation between fly ash size, coal ash content, and K sub 2. Electrical charge and method of coal firing exhibited weak correlations. However, coal sulfur content, fusion properties, and chemical structures showed no clear-cut correlations. The relevant literature on pulse-jet filter theory was assessed to develop guidelines for developing a predictive model. The effects of jet size, air volume, and pulse intensity were related to pressure loss. Energy transfer from the jet pulse to the fabric was explored. Finally, predictive equations were developed for estimating total pressure loss over a range of collector design and operating parameters.