Valerio Ferracci (@atmosvf.bsky.social)

Mitigation of Indoor Ozone and Secondary Products from 222 nm Germicidal Ultraviolet Light Using Commercial Air Cleaners Far ultraviolet-C (UVC) light, especially germicidal UV light at 222 nm (GUV222), has received considerable attention for its potential to deactivate airborne pathogens indoors and prevent the spread of infectious disease. However, GUV222 also generates ozone (O3), posing human health risks and initiating additional photochemistry that may degrade indoor air quality. Air cleaners present an opportunity to counteract the drawbacks of GUV222 by removing harmful byproducts; however, to our knowledge, this has never been demonstrated. Here, we conduct laboratory experiments in a 7.5 m3 Teflon chamber using two commercially available air cleaners─a manganese-oxide-catalyst “ozone cleaner” and an activated-carbon-HEPA “volatile organic compound (VOC) + particulate matter (PM) cleaner”─each simultaneously with a GUV222 lamp. We show that both cleaner types remove a wide range of key pollutants, including O3, NO2, formaldehyde, VOCs, and particles. Application of chamber results to a photochemical model simulating chemistry in a 150 m3 room suggests that a single cleaner can achieve modest reductions in O3 levels and substantial reductions in secondary pollutant levels within typical indoor environments. These results indicate that indoor air pollutants from GUV222 can be mitigated through the use of air cleaning technology, thereby improving indoor air quality while maximizing the potential benefit of germicidal UV for human health. https://pubs.acs.org/doi/10.1021/acsestair.5c00138