Experimental filtration tests were carried out in a hot gas filtration facility with two different dusts (coal ash and gasifier char) using high-temperature fabric filters made from Nextel(TM) 312 ceramic fibers. The filtration efficiency and conditioning behaviour of these filters were investigated for a variety of operating conditions, including face velocity, solids loading, temperature, pulse duration and maximum pressure-drop setting under both reducing and oxidizing conditions simulating gasification and combustion, respectively. Significant differences in the conditioning behaviour of the fabric filter were observed with the two types of dust. Pressure-drop variations as a function of time were investigated for a variety of conditions. A drastic decrease in the pulse interval and a linear increase in the baseline pressure drop were observed when the face velocity was increased, The test results showed that the filtration efficiency was primarily affected by the face velocity. The filter bags demonstrated high filtration efficiencies (i.e. 99.95-99.99%) for a face velocity in the range of 12-24 mm s(-1). At a face velocity of 40 mm s(-1) the filtration efficiency was reduced to 99.5%. (C) 1997 Elsevier Science B.V.