Abstract: A method for on-the-fly detection and separation of multiple checks or like documents transported in a track, wherein the documents are first subjected to twin opposed vacuum forces from a suction source, to separate multiple documents; then a measuring and analysis of the resulting pressure differentials is taken within the vacuum-forming system; the system being provided with a cyclonic filter-separator upstream of the suction source, for removing a storing dust and debris entrained within the vacuum-forming air flow; the cyclonic filter-separator being designed to provide constant vacuum-forming airflow regardless of the nature or quantity of debris removed and collected; the system also being provided with a pressure sensor to give clear indication of the separated/unseparated state of the passing documents, and to exhibit a variable damping accessory.