Abstract View
A Flexible Particle Filtration Efficiency Measurement System (PFEMS) for N95 Respirators, Surgical Masks, and Novel Filter Media
GREGORY SMALLWOOD, Joel Corbin, Fengshan Liu, Jalal Norooz Oliaee, Ian Leroux, Prem Lobo, National Research Council Canada
Abstract Number: 511
Working Group: The Role of Aerosol Science in the Understanding of the Spread and Control of COVID-19 and Other Infectious Diseases
Abstract
Shortages of N95 respirators, surgical masks, and related filter media (collectively referred to as filtration samples) during the COVID-19 pandemic has led to a rush of filtration sample production, including those from many companies new to the field. These filtration samples have been tested using a number of protocols, including NIOSH TEB-APR-STP-0059 (developed for certifying the industrially-targeted N95 respirator), ASTM F2100/F2299 (required for US FDA Particle Filtration Efficiency (PFE)), GB 2626 (China), and other related tests. While all of these protocols may be described as using particles with count median diameter of approximately 100 nm, differences in the face velocity and test particle properties (including size and material density) as well as aerosol neutralization may lead to different results obtained for the same filtration samples when tested in accordance with these different protocols.
In order to rapidly provide filtration efficiency data compatible with all of the above testing protocols, the National Research Council of Canada (NRC) has developed a flexible measurement system to evaluate the performance of filtration samples (particle filtration efficiency measurement system; PFEMS). PFEMS is based on pairs of condensation particle counters (CPCs) and scanning mobility particle sizers (SMPSs), and was initially designed as a modification of the NIOSH protocol. Using NaCl and polystyrene latex (PSL) aerosols, and utilizing a variable face velocity, we demonstrate that PFEMS is a highly flexible and rigorously validated system for simultaneously measuring the flow resistance (pressure drop), number-based filtration efficiency (NFE) and size-resolved filtration efficiency (SRFE), as well as determining mass-based filtration efficiency (MFE), of filter media, surgical and other masks, and respirators using aerosol research instrumentation.
An overview of filtration efficiency testing, the capabilities of the NRC PFEMS, and the physical causes of inconsistent results between the protocols are discussed.