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

Abstract

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 and disinfecting indoor spaces 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. We measured the total irradiance of one GUV222 lamp at a distance of 5 cm away from the source to be 27.0 W m-2 +/- 4.6 W m-2 in the spectral range of 210 nm to 230 nm, with peak emission centered at 222 nm and evaluated the potential for the lamp to generate O3 in a 31.5 m3 stainless steel chamber. In seven four-hour experiments average O3 mixing ratios increased from levels near the detection limit of the instrument to 48 ppbv +/- 1 ppbv (94 ug m-3 +/- 2 ug m-3). We determined an average constant O3 generation rate for this lamp to be 1.10 mg h-1 +/- 0.15 mg h-1. Using a radiometric method and chemical actinometry, we estimate effective lamp fluences that allow prediction of O3 generation by the GUV222 lamp, at best, within 10 % of the measured mixing ratios. Because O3 can react with gases and surfaces indoors leading to the formation of other potential by-products, future studies should evaluate the production of O3 from GUV222 air cleaning devices.