Performance of mechanical filters used in general ventilation against nanoparticles

Abstract

With an equal mass, nanoparticles (NP) have a higher toxicity than particles with the same chemical composition but with larger surface area. However, the toxicological knowledge concerning NP is still insufficient to establish limit values of exposure. To seek the lowest exposure level, filtration is a simple and effective way to capture particles, including NP. According to ANSI/ASHRAE 52.2 standard, ventilation filters efficiency is tested for particles ranging from 0.3 to 10.0 μm. Performances of entire filters for NP are still very limited and particle size of 300 nm (0.3 μm) is commonly used as the most penetrating particle size (MPPS) for mechanical media. To evaluate the filter performance for NP, five type of filters were investigated to measure their performance for particles smaller than 300 nm including NP. The performance of these filters was evaluated in terms of penetration and pressure drop. Experimental data permit to evaluate the MPPS for these mechanical filters. Nevertheless, 150–500 nm range provides a better estimation of the MPPS in the conditions which were tested. Also, filtration velocity influences efficiency for nanoparticles at 50 nm but no effect was observed for MPPS.