Development of a Procedure to Measure the Effectiveness of Electret N-95 Respirator Filter Media for Capturing Nano-Particles

The phenomenal growth of the nano-technological products and their impacts on our society led government organizations and scientists to consider the risks related to human exposure to nano-particles (NPs). As a precautionary approach, respiratory protection is suggested for workers to reduce their exposure to NPs. Thus, it is important to characterize the performance of these respirators to capture NPs. In this study, the performance of one model of N95 respirators was characterized against poly and mono-disperse NPs. With poly-disperse NPs, a methodology was developed to measure the performance of the N95 respirators against NaCl aerosols in the size range of 15 to 200 nm in three scenarios. The N95 respirator performance was also characterized at 85 liters/min against twelve mono-size aerosols with size ranging from 20 to 200 nm. Using poly-disperse aerosols test (PAT) method; the results demonstrated that the initial penetration was significantly enhanced with the increased airflows and a shift toward small particle size was observed for the most penetrating particle size (MPPS). For particles below 100 nm, the penetration decreased with further loading. The MPPS was also found to shift toward the large sized particles. In addition, the penetration augmented slightly as the (RH) increased. Using mono-disperse aerosol test (MAT) method; the results revealed the initial particle penetration is less than 5% NIOSH certification criterion. However, it was found that the initial value, measured with (MAT) method, is not related with the initial penetration measured with (PAT) method at each corresponding particle size at 85 liters/min