Investigation of a DNA tagged aerosol tracer method for In Situ evaluation of germicidal UV air cleaner effectiveness

Abstract

Transmission of respiratory pathogens occurs primarily in indoor settings, interventions to reduce the risk of their transmission include increases in outdoor air introduction, filtration, and ultraviolet germicidal irradiation (UVGI). However, validating these interventions is challenging, particularly in actual applications. This study introduces an aerosol tracer system utilizing DNA as tracer molecule, aimed at quantitative characterization of the performance of indoor air cleaning systems. Two DNA tracers, designed one to be relatively UV-resistant and another relatively UV-sensitive, were employed to assess air quality changes related to filtration and ventilation and the contributions of UVGI fixtures in various built environments. We conducted controlled UV exposure experiments of DNA-tagged tracers on foil coupons, aerosolization studies in a test chamber, and in a commercial building conference room. The DNA tracer results provided insights at the point of sampling into the effects of complex airflow dynamics. Additionally, a way to scale the DNA tracer results to MS2 bacteriophage is proposed. Four distinct UV devices challenged with MS2 in a chamber test produced equivalent clean airflow rates of 13–147 CFM. Scaled equivalent clean airflow rates in a commercial building setting using the UV-sensitive tracer varied from 47 percent less to 101 percent more than the chamber results, possibly due to differences in airflow patterns, equipment configuration, and other factors. Our findings provide quantitative understanding of the interaction between UV-sensitive aerosols and the built environment, with implications for environmental monitoring, measuring UVGI fixture impact in field settings, and addressing current technologies limitations for assessing UVGI disinfection efficacy.