Penetration of Nanoparticles through Respirator Filter Media

摘要

In this study, nanoparticle penetration was tested for with a wide range of filter media (four fiberglass filter media, four electret filter media and one nanofiber filter media) using silver nanoparticles from 3 nm to 20 nm at face velocities of 5.3, 10 and 15 cm/s. The silver particles were generated by heating a pure silver powder source via an electric furnace with a temperature of 870 degrees C, which is the optimal temperature for generating adequate amounts of silver nanoparticles for the size range specified above. After size classification using a nano-DMA, the particle counts were measured by a UCPC both upstream and downstream of the test filter to determine the nanoparticle penetration for each particular particle size. Particle sampling time continued long enough to detect more than 10(5) counts at the upstream and 10 counts at the downstream sampling point so that 99.99% efficiency can be detected with the high efficiency filter. Each test was repeated more than five times by different operators, at different dates and with different samples from each filter medium in order to reduce any possible error. The results show a very high uniformity with small error bars for all filter media tested in this study. The particle penetration decreases continuously down to 3 nm as expected by the traditional filtration theory, and together with a companion modeling study by Wang et al. (2006), we found no evidence of nanoparticle thermal rebound down to 3 nm.