To minimize worker exposure to nanoparticles, a team of researchers has developed a methodology to assess the effectiveness of respiratory protective devices (RPDs) by reproducing, in a laboratory, conditions of exposure to particles of various sizes. Using an experimental test bed fitted with an air purification device, the scientists analyzed the performance of N95 filters, the type most commonly used; in addition, they studied the effect of air flow and particle size on the penetration of particles through the RPD, and the effect of duration of use and relative humidity on the efficiency of the filtration. The filters were tested at high airflow rates, specifically, constant flow rates of 85, 135, 270 and 360 litres of air per minute.
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