A Study Of The Mechanism Of Wet And Dry Filtrationrnusing Nist Traceable Glass Microspheres

摘要

The objective of this work was to investigate the performance differences in filter media depending on whether the challenge test is conducted in the dry state or using a liquid suspension of microspheres. Comparisons of filter cut points between a pulsed airflow and a single pass liquid suspension method were used to investigate the mechanisms of filtration. Depth filtration effects were examined by comparing 2-dimensional filters (precision electro-formed filters) to moderate depth filters (pillow fabric and needle felts) and a 3-dimensional depth filter (water cartridge filters). No differences were found for 2-dimensional filters but significant differences in performance were found between wet and dry analysis of 3-dimensional filters. There was little evidence of secondary filtration in the suspension method for concentrations from 0.2% down to 0.025%.