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(a) Size-dependent filtration efficiency of a combination of filter media and (b) pressure drop tested as multi-layer 47 mm punches measured in a filter-holder-based system. (Flow rate: 4.37 L/min, punch: 47 mm, aerosol: 0.3 M NaCl, NTOT: 2 × 106 #/cm3, RH: 32–35%, and scan-time: 1 min (SMPS).
