Effects of nanosized water droplet generation on number concentration measurement of virus aerosols when using an...

Development of efficient virus aerosol monitoring and removal devices requires aerosolization of the test virus using atomizers. The number concentration and size measurements of aerosolized virus particles are required to evaluate the performance of the devices. Although diffusion dryers can remove water droplets generated using atomizers, they often fail to remove them entirely from the air stream. Consequently, particle measurement devices, such as scanning mobility particle sizer (SMPS), can falsely identify the remaining nanosized water droplets as virus aerosol particles. This in turn affects the accuracy of the evaluation of devices for sampling or removing virus aerosol particles. In this study, a plaque-forming assay combined with SMPS measurement was used to evaluate sufficient drying conditions. We proposed an empirical equation to determine the total number concentration of aerosolized particles measured using the SMPS as a function of the carrier air flow rate and residence time of the particles in the diffusion dryers. The difference in the total number concentration of particles under sufficient and insufficient diffusion drying conditions was presented as a percentage of error.