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. 2010 Oct;41(10):944-952.
doi: 10.1016/j.jaerosci.2010.07.003. Epub 2010 Jul 8.

Method for contamination of filtering facepiece respirators by deposition of MS2 viral aerosols

Myung-Heui Woo  1 , Yu-Mei Hsu  2 , Chang-Yu Wu  1 , Brian Heimbuch  3 , Joseph Wander  4
Affiliations

Method for contamination of filtering facepiece respirators by deposition of MS2 viral aerosols

Myung-Heui Woo et al. J Aerosol Sci. 2010 Oct.

Abstract

A droplet/aerosol loading chamber was designed to deliver uniform droplets/aerosols onto substrates. An ultrasonic nebulizer was used to produce virus-containing droplets from artificial saliva to emulate those from coughing and sneezing. The operating conditions were determined by adjusting various parameters to achieve loading density and uniformity requirements. The count median diameter and mass median diameter were 0.5-2 and 3-4 μm, respectively, around the loading location when 35% relative humidity was applied. The average loading density was ∼2×103 plaque-forming units/cm2 for 5-min loading time with a virus titer of 107 plaque-forming units/mL. Six different filtering facepiece respirators from commercial sources were loaded to evaluate uniform distribution. For each of the six FFRs, the virus loading uniformity within a sample and across numerous samples was 19.21% and 12.20%, respectively. This system supports a standard method for loading viable bioaerosols onto specimen surfaces when different decontamination techniques are to be compared.

Keywords: Coughing; Droplet; Loading chamber; Loading density; Uniformity.

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Figures

Fig. 1
Fig. 1
Schematic diagram of droplet loading system: (A) entire system, (B) distributor on top, (C) turntable, (D) air outlet at bottom ((a) and (b) are needed only in certain conditions).
Fig. 2
Fig. 2
Loading density as a function of (A) loading time and (B) virus titer in the nebulizer.
Fig. 3
Fig. 3
CVs for Q-T-Q and S-T-S as a function of turntable speed.
Fig. 4
Fig. 4
Scanning electron microscopy images (250×) of an FFR (A) before loading and (B) after loading for 1 min.
Fig. 5
Fig. 5
(A) Number- and (B) mass-based size distribution of droplets generated by ultrasonic nebulizer at five flow rates.
Fig. 6
Fig. 6
The number- and mass-based particle size distribution of generated droplets and loaded droplets at 2 Lpm through the aerosol generator plus 3 Lpm dry air and 2-rpm turntable speed.
Fig. 7
Fig. 7
Recovery of viable MS2 as a function of extraction time for three FFRs.
See this image and copyright information in PMC

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