Development and Validation of a Large-Scale Controlled Aerosol Chamber to Evaluate Air Purifier Efficiency Against Live Viral Aerosols
VINCENT BROCHU, Marc Veillette, Nathalie Turgeon, Gregory Nilsson, Liang (Grace) Zhou, Caroline Duchaine, Université Laval
Abstract Number: 177
Working Group: Bioaerosols
Abstract
Introduction
During the COVID-19 pandemic, air purifying devices were utilized to clear airborne viral aerosols in multi-occupancy spaces such as hospital wards, classrooms, conference rooms, etc. While these devices are typically tested in confined spaces against various particulate matter such as smoke, dust, and pollen, their efficiency in the inactivation and removal of viral aerosols has not been adequately assessed. This study aims to develop a method for evaluating the efficacy of air purifier specifically against viral particles.
Procedure
MS2 bacteriophage was aerosolized within a 10 m3 aerosol chamber with controlled air exchange rate using a Collison 6-jet nebulizer. Viruses were sampled directly onto Tryptic Soy Broth Petri Dishes previously inoculated with MS2’s host strain using two Slit-to-Agar devices, positioned in the middle of the chamber. Following sampling, Petri dishes were incubated overnight (37°C). Additionally, particles were counted using an Aerodynamic Particle Sizer (APS). Air exchange rates per hour were calculated from the concentration decays measured by the APS and by culture methods adhering to the ASTM-E741 standard. Air exchange rates were compared with and without the use of the air purifier to assess its efficiency and the validity of the method.
Results and Discussion
The viral decay and measured air exchange rate were consistent with the use of the settings of the air purifier (off, 50%). The time resolution of the two Slit-to-Agar devices indicates homogeneous air mixing within the chamber. However, viral decay did not mirror particle decay patterns, as air exchange rates calculated based on particle concentrations often exceeded those based on viruses decays. Computational Fluid Dynamics (CFD) modeling will be employed to describe air movements within the chamber, and additional types of air purifiers will be tested.
Funding
This project is funded by the National Research Council of Canada.