Determination of Bipolar Ionization-Mediated Airborne Virus Inactivation Rates
DARRYL ANGEL, Jordan Peccia,
Yale University Abstract Number: 459
Working Group: Aerosol Science of Infectious Diseases: Lessons and Open Questions on Models, Transmission and Mitigation
AbstractReducing the concentration of infectious viral aerosols within indoor settings is essential for decreasing infectious risk. Common airborne virus concentration reduction approaches, including outdoor air ventilation, HVAC (heating, ventilation, and air conditioning) system filtration, and in-duct ultraviolet germicidal irradiation are limited by the air exchange rates that can be achieved in a building. Similar to drinking water treatment, directly disinfecting a building’s bulk air with a non-toxic disinfectant is a more effective strategy for reducing airborne infection. Bipolar ionization (BPI) is a currently utilized building bulk-air disinfection technology with the potential to reduce airborne virus concentrations through two proposed mechanisms: facilitating particle agglomeration to increase virus deposition onto building surfaces, and loss of viral infectivity caused by ion-induced damage to viral surface proteins. We determined bipolar ionization-mediated first order inactivation rate coefficients for aerosolized bacteriophage Phi6, a common surrogate organism for SARS-CoV-2. At ~49% relative humidity (RH), the total (0.15 1/min to 0.22 1/min; p<0.01) and infectious (0.31 1/min to 0.50 1/min; p<0.01) Phi6 decay rate coefficients increased when average bipolar ion exposure was increased from a baseline of 10^3 ions/cm^3 to experimental conditions of 10^6 ions/cm^3. The same significant increase (p<0.01) in total and infectious Phi6 decay was present at high (~76%) RH in the presence of additional bipolar ions. While we observed no difference between total Phi6 decay rates at low (~26%) RH (p>0.05) between the two bipolar ion concentrations, the inactivation of infectious Phi6 owing to BPI remained significant (p<0.05) but lower than the values measured under middle and high RH. Across all RH levels, the inactivation of infectious Phi6 attributable to BPI was greater than the natural decay of Phi6.