Evaluation of N95 Filtering Facepiece Respirators Challenged with Engineered Nanoparticles

Abstract

NIOSH-certified respirators, including N95 respirators, are recommended when engineering and administrative controls do not adequately prevent exposures to airborne nanomaterials. Laboratory evaluations of filtering efficiency using standard test aerosols have been reported in the literature, but there is no information on penetration of engineered nanoparticles (1-100 nm) for N95 filtering facepiece respirators (FFR). This project evaluated the performance of two manufacturers' N95 FFR filters challenged with engineered nanoparticle aerosols containing metal oxides (such as TiO 2 ) and carbon (such as fullerenes and nanotubes) in contrast with a sodium chloride (NaCl) aerosol at flow rates of 30, 85, and 130 L min -1 . For new respirator filters in general, NaCl aerosol penetration was less than 5% and the most penetrating particle size occurred at 40 nm. Overall penetration of the engineered nanoparticle aerosols exceeded 5% and was often greater than 5% at and near the most penetrating particle size (MPPS), which occurred at a larger particle size range (90-150 nm). For respirators treated with isopropanol in which the electrostatic force was removed, penetration of NaCl and engineered nanoparticles increased substantially and the MPPS increased to 150 nm for both types of aerosols. Our results indicated that a possible reason for higher maximum penetrations and shift of MPPS observed for these engineered nanoparticles in the new respirators was related to electrostatic collection processes.

Effects of size and shape on filtration of TiO2 nanoparticles

“…Performance evaluation of filters and respirators using nanoparticles showed diffusion and interception are the dominant deposition mechanisms for ultrafine particles (Cheng and Yeh 1980;Ichitsubo et al 1996;Kim et al 2007;Rengasamy et al 2009;Chen et al 2014Chen et al , 2015Zhou and Cheng 2016). Experimental data agreed with the filtration theory for spherical particles in fan model filters such as screen filters Kirsch and Chechuev 1985;Ichitsubo et al 1996) and in Nuclepore filters (Chen et al 2015).…”

Microbial Growth on Dust-Loaded Filtering Materials Used for the Protection of Respiratory Tract as a Factor Affecting Filtration Efficiency

“…The obtained penetration values (for control samples) are higher than previously reported in the literature [ 24 ], which may be the result of the applied disinfection process in isopropyl alcohol vapours that could lead to a partial discharge of electret material, and hence the weakening of the electrostatic interaction between the fibres and the aerosol particles. This observation is consistent with the previous findings showing diminishing effect of isopropyl alcohol treatment on the electret performance of nonwoven filters [ 25 , 26 , 27 ]. For control nonwovens, no effect of microbial growth on penetration was observed, while for nonwovens loaded with dust A, the differences occurred only in the particle size range of 20-110 nm.…”

Multi-Scale Microstructure Investigation for a PM2.5 Air-Filter Efficiency Study of Non-Woven Polypropylene

“…To satisfy high collection efficiency of fibrous filters for further applications, electret filters have been widely applied in the manufacture of commercial air filter media. Electret filters are dielectric materials-based fibrous filters that possess quasi-permanent static electric charge on the fiber surfaces [7] in which the electrostatic force dramatically enhances filtration efficiency and is responsible for the main capture of fine aerosol particles, resulting in a significant shift towards a smaller particle size of MPPS [8][9][10][11].…”