Variations of collection efficiencies and pressure drops through bag filters have been investigated experimentally. It was found that the collection efficiencies decreased exponentially or linearly with increases of particle diameter or dust loading, respectively; they increased exponentially with the filter surface area, were found to be independent of dust-particle material and filtration velocity, and had the greatest values for P&S and Egyptex fabric materials. The pressure drop across the fabric and collected dust layer increased exponentially from 14 to 36 mm of water with an increase of dust loading on the filter from 0 to 1300 g/m(2). The experimental results were fitted to an empirical equation.