Effects of Germicidal Far-UVC on Indoor Air Quality in an Office Setting

The application of 222 nm light from KrCl excimer lamps (GUV222 or Far-UVC) is a promising approach to reduce the indoor transmission of airborne pathogens, including the SARS-CoV-2 virus. GUV222 inactivates airborne pathogens and is believed to be relatively safe for human skin and eye exposure. However, UV light initiates photochemical reactions which may negatively impact indoor air quality. We conducted a series of experiments to assess the formation of ozone (O3) and secondary organic aerosols (SOA) induced by commercial far-UVC devices in an office environment with an air exchange rate of 1.3 h-1. We studied scenarios with a single far-UVC lamp, corresponding to the manufacturer’s recommendations, and with four far-UVC lamps, which exceeded both the manufacturer’s and regulatory recommendations. The single far-UVC lamp did not significantly impact O3 or fine particulate matter levels. Consistent with previous studies in the literature, the higher far-UVC fluences lead to increases in O3 of 5 to 10 ppb above background, and minor increases in particulate matter. The use of far-UVC at intensities consistent with regulatory / manufacturer’s recommendations, and in conjunction with normal ventilation, may reduce airborne pathogen levels while minimizing the formation of air pollutants.