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 while posing a minimum risk to human tissue. However, 222 nm light can produce ozone (O 3 ) in air. O 3 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 4 h experiments, we measured the production of O 3 from a single filtered GUV222 lamp in a 31.5 m 3 stainless steel chamber. Using an emission model, we determined an O 3 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 production of O 3 in our chamber within 20% of the average measured mixing ratio. Future studies should evaluate the indoor air quality impacts of GUV222 technologies.

Indoor Air Quality Implications of Germicidal 222 nm Light

“…More quantitative estimates of UV fluence rate and its relationship to O 3 generation are available in recent work by Peng et al . and Link et al Most experiments are carried out at full light intensity. For “low-light” experiments, the lamp emission is attenuated by several layers of plastic, achieving a factor of ∼5 reduction in intensity (determined by the reduction in the steady-state O 3 concentration, which is assumed to scale linearly with average UV fluence). , For the “O 3 -only” experiments, the light is left off, and O 3 is introduced via a Pen-Ray ozone generator, with a steady-state O 3 concentration matching that of the GUV 222 experiments (∼100 ppb).…”

“…The indirect estimation of the lamp intensity is a limitation of this work, but the agreement between modeled and measured ozone production (see Results and Discussion Section) indicates that it is reasonably accurate. More quantitative estimates of UV fluence rate and its relationship to O 3 generation are available in recent work by Peng et al 22 and Link et al 21 Most experiments are carried out at full light intensity. For "low-light" experiments, the lamp emission is attenuated by several layers of plastic, achieving a factor of ∼5 reduction in intensity (determined by the reduction in the steady-state O 3 concentration, which is assumed to scale linearly with average UV fluence).…”

“…However, the extent and nature of this impact remain quite uncertain, even as GUV 222 is being deployed in indoor spaces . Two very recent experimental studies , demonstrate O 3 production from GUV 222 , but these do not examine the overall effects on indoor air quality (including the production of OH, OVOCs, and SOA) by GUV 222 . To the best of our knowledge, the only published work to do so is a box-modeling study by Peng et al That work predicted that 222 nm irradiation could lead to elevated levels of O 3 and other secondary species relative to nonilluminated conditions, especially under low-ventilation conditions.…”

Quantification of Byproduct Formation from Portable Air Cleaners Using a Proposed Standard Test Method

“…We have demonstrated in a previous study the formation of O 3 from a GUV222 device, but here we have supplemented those observations with measurements of VOC and UFP byproducts. Compared to the PECO/PCO technologies, the UV-based technologies removed less of the challenging chemicals and produced less VOC byproducts.…”

Effects of 222 nm Germicidal Ultraviolet Light on Aerosol and VOC Formation from Limonene

“…One limitation of using 254 nm UV (GUV254) fixtures for air disinfection is that they are not safe for human exposure, so they are usually either mounted near the ceiling for upper room irradiation or used inside ventilation ducts. , Studies have shown that 222 nm lamps can be used for whole-room disinfection to inactivate airborne bacteria and viruses without harm to human skin and eyes. − However, it has also been shown that GUV222 forms substantial ozone, which can react further in the indoor environment to form harmful pollutants like formaldehyde and PM 2.5 . − …”