Validation of a Laboratory Test Bench for the Efficiency of an N95 Filtering Face Piece, using Simulated Occupational Exposure

Abstract

Ultrafine particles (<100 nm) have special properties that nanotechnologies seek to exploit. However, due to their nanometric scale, these particles can be deposited in the lungs and cause damage. Based on current knowledge, occupational exposure to nanoparticles occurs mainly in workplaces handling nanomaterials, or when certain processes generate them indirectly. However, there are currently no limit values for exposure to ultrafine particles. To limit worker exposure, respiratory protective devices (RPD) are generally used. The aim of this study was to determine if (a) a laboratory test bench and (b) a simulated occupational exposure setup were reliable representations undesirable exposure in workplace. Thus, two tests benches were used to compare on the one hand conventional measurements and on the other hand sanding- simulation process measurements. NaCl aerosols were generated and then used to measure penetration with constant flow at 43 L/min, 85 L/min and 135 L/min, and one cyclic flow defined by 85 L/min as the mean inhalation flow. The results showed that initial penetrations were less than 5%, as required by the certification. The results also showed that there was a high correlation between the two penetration measurements. One also notes that the measurements had a slightly higher maximum penetration with a charge- neutralized NaCl aerosol than with an un-neutralized NaCl aerosol. The charged-neutralized particles constituted the worst-case scenario exposure.