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.