Dust masks are often confused with filtering facepiece respirators (FFR) but are not approved by NIOSH for respiratory protection against particulate exposure. This study reports the filtration performance of commercially available dust masks against submicron particles and discusses the relevance of these findings toward the filtration of nanoparticles. Seven different models of dust masks from local home improvement/hardware stores were challenged with submicron NaCl particles, and initial percentage penetration and resistance levels were measured using two test procedures. A polydisperse aerosol test (PAT) method, similar to the "worst case" conditions used in the NIOSH particulate respirator certification test protocol was used. A monodisperse aerosol test (MAT) method, which utilizes eleven different particle sizes in the range of 20-400 nm, were also used for particle penetration measurements at 30 and 85 L/min flow rates using the TSI 3160. Dust masks were designated as category low-, medium- and high-penetration dust masks based on penetration levels of <5%, 5-25% and >25%, respectively. Data collected using the PAT and the MAT methods showed <5% initial penetration levels for low-penetration dust masks, which is similar to the NIOSH-approved class-95 filtering facepiece respirators. Average penetration levels for medium- and high-penetration dust masks were between 8.9-24.2% and 74.5-96.9%, respectively. Penetration levels of MPPS particles from the MAT correlated with penetration levels from the PAT. Monodisperse MPPS penetration levels from MAT and penetration levels from PAT showed poor correlation with resistance values and no correlation with cost. The results of this study show that dust masks frequently do not provide filtration performance equivalent to that of NIOSH certified devices. Users of dust masks should be cautioned against using them for protection against particulates in the nano- or ultrafine size ranges.
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