Far-UVC Generated Ozone Levels in a Hotel and Comparison to Outdoor Concentrations
PETRI KALLIOMÄKI, Phillip Stratton, Kristen K. Coleman, Aditya Kiran Srikakulapu, Ross Salawitch, Russell R. Dickerson, Shengwei Zhu, Jelena Srebric, Donald K. Milton,
University of Maryland Abstract Number: 432
Working Group: Aerosol Science of Infectious Diseases: Lessons and Open Questions on Models, Transmission and Mitigation
AbstractFar-UVC (222 nm UV light) is a promising tool to mitigate aerosol transmission of infections indoors. However, concerns related to ozone production and secondary chemistry (like formation of secondary organic aerosols) have been raised. Data related to indoor ozone concentrations in real-world settings are also lacking.
In this study, we measured ozone concentrations and fine particles (17-500 nm) with and without 222 nm far-UVC in a regular guest room and in a well-sealed test room in a hotel in downtown Baltimore (MD) between February 16
th and March 10
th (2023). The baseline ventilation rate was 0.3 air changes per hour (ACH) in the well-sealed room and 1.3 ACH in the regular room. The UV power intensity was 4.6 mW/m
3 in the well-sealed room and 5.5 mW/m
3 in the regular room. Indoor ozone concentrations were compared to outdoor concentrations (EPA Ambient Air Monitoring Network) around the Baltimore area.
In the well-sealed room, the average ozone concentration was 2 ppb when the UV lights were off and 13 ppb when on, compared to average outdoor concentrations of 22 ppb and 23 ppb, respectively. The average ozone concentration in the regular room was 10 ppb when UV was off and 12 ppb when UV was on, compared to average outdoor concentrations of 35 ppb and 27 ppb, respectively. Particle measurements did not show a clear signal related to UV usage.
Although indoor ozone levels increased during far-UVC usage, the concentrations remained lower than outdoors. The effect of infiltration on indoor ozone concentrations can also be significant, especially if buildings are not well sealed. Nonetheless, more information related to factors governing ozone concentrations and secondary chemistry (e.g. secondary organic aerosols) in buildings is needed.