Far‐UVC (222 nm) efficiently inactivates an airborne pathogen in a room‐sized chamber

Ewan Eadie1*, Waseem Hiwar2, Louise Fletcher2, Emma Tidswell2, Paul O’Mahoney1,3, Manuela Buonanno4, David Welch4,

Catherine S. Adamson5, David J. Brenner4, Catherine Noakes2 & Kenneth Wood6

Eadie 2022 _ Far‑UVC (222 nm) inactivates airborne S. Aureus in a room‑sized chamber.pdf

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Many infectious diseases, including COVID‐19, are transmitted by airborne pathogens. There is a need for effective environmental control measures which, ideally, are not reliant on human behaviour. One potential solution is Krypton Chloride (KrCl) excimer lamps (often referred to as Far‐UVC), which can efficiently inactivate pathogens, such as coronaviruses and influenza, in air. Research demonstrates that when KrCl lamps are filtered to remove longer‐wavelength ultraviolet emissions they do not induce acute reactions in the skin or eyes, nor delayed effects such as skin cancer. While there is laboratory evidence for Far‐UVC efficacy, there is limited evidence in full‐sized rooms. For the first time, we show that Far‐UVC deployed in a room‐sized chamber effectively inactivates aerosolised Staphylococcus aureus. At a room ventilation rate of 3 air‐changes‐per‐hour (ACH), with 5 filtered‐ sources the steady‐state pathogen load was reduced by 98.4% providing an additional 184 equivalent air changes (eACH). This reduction was achieved using Far‐UVC irradiances consistent with current American Conference of Governmental Industrial Hygienists threshold limit values for skin for a continuous 8‐h exposure. Our data indicate that Far‐UVC is likely to be more effective against common airborne viruses, including SARS‐CoV‐2, than bacteria and should thus be an effective and “hands‐off” technology to reduce airborne disease transmission. The findings provide room‐scale data to support the design and development of effective Far‐UVC systems.