Performance of respirator filters using quality factor in Korea

A respirator filter of good quality has not only high aerosol collection efficiency but also low air resistance. "Quality factor", which is expressed with aerosol penetration and pressure drop, can be used to rank the performance of respirator filters within the same category. This study focuses on evaluating several respirator filters which are widely used in Korea using quality factor. Two mechanical filters and three filtering facepieces made by different manufacturers were measured aerosol penetrations and pressure drops by an automatic filter tester (CertiTest Model 8110, TSI Inc., St. Paul, USA) at four flow rates of 10, 32, 64 and 85 L/min. NaCl aerosols used were reported to be mean size of 0.1 microm and geometric standard deviation of <1.9. The penetrations and pressure drops of all filters have strong flow rate dependency. The filter quality factors decrease sharply as flow rates are increased. The mechanical filter S and filtering facepiece M are shown better filter quality than others in the same category. Since some certified filters are found to be inappropriate in the workplace exposed to fume, this result suggests that the current certified filter test protocol for respirators should be changed for the new protocol using smaller aerosols.