Atmospheric Nanoparticle Growth Dynamics with the Application of Whole-Room Far-UVC Radiation

BRIAN MAGNUSON, Shohoria Afrin Shorno, Chunxu Huang, Ernest Blatchley III, Brandon E. Boor, Nusrat Jung, Purdue University

     Abstract Number: 307
     Working Group: Indoor Aerosols

Abstract
Far-UVC radiation (222 nm) is an effective method for the inactivation of pathogens through whole-room irradiation with its low potential for damaging the skin and eyes of occupants. However, studies have shown that Far-UVC applications can lead to the formation of byproducts such as ozone. In indoor environments, reactions between ozone and volatile organic compounds (VOCs) can result in the formation of atmospheric nanoparticles, which grow via coagulation and condensation. While Far-UVC radiation can effectively inactivate airborne pathogens, the generation and growth of these nanoparticles introduces a potential respiratory exposure risk. We conducted field experiments in the Purdue zero Energy Design Guidance for Engineers (zEDGE) Test House, representative of a residential environment, to investigate atmospheric nanoparticle formation and growth during Far-UVC irradiation. Krypton Chloride (KrCl) excimer lamps were ceiling-mounted for whole-room exposure. Twenty-four-hour experiments with timed lamp activation were performed to account for diurnal fluctuations in ambient ozone levels. Particle size distributions from 10 to 500 nm were measured using a scanning mobility particle sizer (SMPS), and indoor/outdoor ozone was monitored with ozone analyzers. We observed clear particle growth in the 10 to 100 nm range during Far-UVC operation, with number concentrations increasing by up to fourfold. Upon lamp deactivation, concentrations returned to background levels. We will report estimated particle growth rates under different experimental conditions to assess the roles of coagulation and condensation in driving nanoparticle evolution. These findings highlight nanoparticle formation and growth as a secondary consequence of Far-UVC use in indoor spaces and underscore the need for mitigation strategies to reduce potential health risks.