Ozone Generation from a Germicidal Ultraviolet Lamp with Peak Emission at 222 nm

Recent interest in commercial devices containing germicidal ultraviolet lamps with a peak emission wavelength at 222 nm (GUV222) has focused on mitigating virus transmission indoors while posing minimum risk to human tissue. However, 222 nm light can produce ozone (O₃) in air. O₃ is an undesirable component of indoor air because of health impacts from acute to chronic exposure and its ability to degrade indoor air quality through oxidation chemistry. In seven four-hour experiments we measured O₃ produced from a single filtered GUV222 lamp in a 31.5 m³ stainless steel chamber. Using an emission model, we determined an O₃ generation rate of 19.4 ppb_v h^-1 ± 0.3 ppb_v h^-1 (equivalent to 1.22 mg h^-1 ± 0.02 mg h^-1). We estimated the fluence rate from the lamp using two methods: (1) chemical actinometry using tetrachloroethylene (actinometry) and (2) geometric projection of the irradiance field from radial and angular distribution measurements of the GUV222 lamp fluence (irradiance). Using the estimated lamp fluence rates of 2.2 μW cm^-2 (actinometry) and 3.2 μW cm^-2 (irradiance) we predicted O₃ production in our chamber within 20 % of the average measured mixing ratio. Future studies should evaluate the indoor air quality impacts of GUV222 technologies.