Do-It-Yourself Air Cleaners as an Emergency Measure to Reduce Indoor Exposure to Respiratory Aerosols

WILLIAM LINDSLEY, Raymond Derk, Jayme Coyle, Francoise Blachere, Stephen Martin, Jr., Kenneth R. Mead, Donald Beezhold, John Noti, National Institute for Occupational Safety and Health

     Abstract Number: 26
     Working Group: Aerosol Science of Infectious Diseases: Lessons and Open Questions on Models, Transmission and Mitigation

Abstract
Portable air cleaners can be used to reduce indoor exposure to infectious airborne pathogens, wildfire smoke, allergens, and other hazardous aerosols. However, during a public health emergency such as the recent COVID-19 pandemic, the need for air cleaners can greatly exceed the available supply and financial resources. Consequently, a variety of do-it-yourself (DIY) air cleaner designs have been developed and widely disseminated. We tested two DIY air cleaner designs in a simulated classroom with a breathing simulator acting as a source of respiratory aerosols and three breathing simulators acting as recipients exposed to these aerosols. Optical particle spectrometers monitored the concentrations of the simulated respiratory aerosol particles (0.3–3 μm) in the breathing zones of the recipient simulators and throughout the room as the particles dispersed. Our results showed that using the DIY air cleaners in various configurations provided an additional 0.4 to 6.6 effective air changes/hour (ACH) per unit above the 2 ACH baseline provided by the room HVAC system. Using two DIY air cleaners and the HVAC system reduced the average aerosol exposures by a range of 41% to 78% compared with using the HVAC system alone. Increasing the number of filters per DIY unit, the filter thickness, and the fan airflow significantly increased the effective air change rate and exposure reductions. Our results show that DIY air cleaners can be an effective means of reducing indoor aerosol exposures. However, they also show that the performance of DIY air cleaners can vary considerably depending upon their design, construction, and positioning, and thus that the lack of quality control testing for DIY air cleaners presents an important limitation to their use. Simple methods to test and monitor the performance of DIY air cleaners need to be developed to ensure that the air cleaners perform as expected.