Development and Characterization of a New Test System to Challenge Personal Protective Equipment with Virus-Containing Particles
Evanly Vo and Ronald Shaffer
Previous bioaerosol test systems used in personal protective equipment (PPE) reuse, performance, and handling research were limited in their ability to generate diverse particle size ranges and types. The objective of this study was to develop and characterize a new test system to challenge PPE with virus-containing particles (VCPs). The new system was designed to achieve two specific research objectives: 1) to be capable of delivering VCPs uniformly onto air permeable PPE such as filtering facepiece respirators (FFRs) and surgical masks (SMs) and 2) to be capable of performing simple VCP filtration tests. The test system consists of two aerosol generators, an exposure chamber, a breathing simulator/head form, and several aerosol detection systems. The test system was validated against the two objectives using two experimental scenarios involving droplet nuclei and droplet VCPs. The size distribution from the droplet nuclei experiments was 0.02 - 10.3 μm, with 96% of particles between 0.2 - 4.0 μm and a mass median diameter of 0.60 μm with a geometric standard deviation (GSD) of 1.64. The size distribution of the droplets was 0.54 - 100 μm, with 83% of particles < 10 m and a median [Dv(50)] of 5.03 m. The amount of viable MS2 deposited on the respirators met ASTM E2720 and E2721 loading requirements, with > 97% found on the outer and middle layers of the N95 FFR models. Average filtration efficiencies were highest for the P100 FFRs (99.91 - 99.94%), followed by N95 FFRs (96.57 - 98.18%) and SMs (78.69 - 80.43%). These data indicate that the test system was able to meet the study objectives and will serve as a versatile tool for standards development and for research studies related to PPE reuse and handling.
Keywords: Bio-aerosol respirator testing system, viral droplets, droplet nuclei, loading density, uniformity, filtration efficiency