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Particle Count Statistics Applied to the Penetration of a Filter Challenged with Nanoparticles
Journal article   Open access   Peer reviewed

Particle Count Statistics Applied to the Penetration of a Filter Challenged with Nanoparticles

Patrick T O'shaughnessy and Linda H Schmoll
Aerosol science and technology, Vol.47(6), pp.616-625
06/01/2013
DOI: 10.1080/02786826.2013.778954
PMCID: PMC3964675
PMID: 24678138
url
https://doi.org/10.1080/02786826.2013.778954View
Published (Version of record) Open Access

Abstract

Statistical confidence in a single measure of filter penetration (P) is dependent on the low number of particle counts made downstream of the filter. This article discusses methods for determining an upper confidence limit (UCL) for a single measure of penetration. The magnitude of the UCL was then compared to the P value, UCL ≤ 2P, as a penetration acceptance criterion (PAC). This statistical method was applied to penetration trials involving an N95 filtering facepiece respirator challenged with sodium chloride and four engineered nanoparticles: titanium dioxide, iron oxide, silicon dioxide, and single-walled carbon nanotubes. Ten trials were performed for each particle type with the aim of determining the most penetrating particle size (MPPS) and the maximum penetration, P max . The PAC was applied to the size channel containing the MPPS. With those P values that met the PAC for a given set of trials, an average P max and MPPS was computed together with corresponding standard deviations. Because the size distribution of the silicon dioxide aerosol was shifted toward larger particles relative to the MPPS, none of the ten trials satisfied the PAC for that aerosol. The remaining four particle types resulted in at least four trials meeting the criterion. MPPS values ranged from 35 to 53 nm with average P max values varying from 4.0% for titanium dioxide to 7.0% for iron oxide. The use of the PAC is suggested for determining the reliability of penetration measurements obtained to determine filter P max and MPPS. © 2013 American Association for Aerosol Research

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