Innovative cartridges (made from traditional yarn, with a wound crisp tow and hybrid structure) were compared to acknowledged leading filter brands, both to characterise the new product and to evaluate the actual performance of commercial products. A pilot plant apparatus was designed and built to reproduce the standard measurements; a solid pollutant was prepared, classified and tested to prove its suitability for the different aspects of the study. Careful analysis of the particle size distribution of the contaminant in the clarified stream and of the contaminant trapped in the fibre framework offered an interpretation of the mechanisms acting on different particle sizes. Structures useful in delaying the cartridge＇s collapse, to reduce the pressure drop and, as a primary property, to guarantee a given efficiency in a wide range of pollutant particle sizes are suggested.