Center for the Built Environment

Far-UVC (222 nm) irradiation effectively inactivates airborne pathogens, but photolyzes oxygen to generate ozone, potentially initiating indoor chemistry that may form secondary pollutants. To evaluate these impacts in a realistic setting, we conducted experiments in a full-scale (158 m3) office chamber. The study involved 13 sessions with human subjects (n=4–8) under typical mechanical ventilation (0.7–0.8 h⁻¹). We monitored ozone, ultrafine particles, and nitrogen oxides, and took time-integrated volatile organic compounds (VOCs) samples before and after the lamps on. We found that while far-UVC operation increased ozone concentrations, the elevation in the occupied room was modest (median increase 1.44 ppb). We didn’t observe discernible secondary aerosol and VOCs formation. Participant surveys indicated that air quality remained acceptable throughout the experiments. These results suggest that in ventilated, occupied offices, far-UVC can be deployed with minimal impact on chemical indoor air quality.