The high- temperature filtration of particulates from gases is greatly limited because of the development of dust cakes that are difficult to remove and can bridge between candle filters, causing them to break. Understanding the conditions leading to the formation of cohesive dust can prevent costly filter failures and ensure higher efficiency of solid fuel, direct- fired turbine power generation systems. The University of North Dakota Energy & Environmental Research Center is working with the New Energy and Industrial Technology Development Organization and the U. S. Department of Energy to perform research to characterize and determine the factors that cause the development of such dust cakes. Changes in the tensile strength, bridging propensity, and plasticity of filter dust cakes were measured as a function of the temperature and a filter pressure drop for a coal and a biomass filter dust. The biomass filter dust indicated that potential filtering problems can exist at temperatures as low as 400 degrees C, while the coal filter dust showed good filtering characteristics up to 750 degrees C. A statistically valid model that can indicate the propensity of filters to fail with system operating conditions was developed. A detailed analysis of the chemical aspect of dusts is also presented in order to explore the causes of such stickiness.