Ocular and Facial Far‐UVC Doses from Ceiling‐Mounted 222 nm Far‐UVC Fixtures

Abstract

Far-UVC radiation, commonly defined as wavelengths from 200 nm -235 nm, is a promising tool to help prevent the spread of disease. The unique advantage of far-UVC technology over traditional ultraviolet germicidal irradiation lies in the potential for direct application of far-UVC into occupied spaces since antimicrobial doses of far-UVC are significantly below the recommended daily safe exposure limits. This study used a ceiling-mounted far-UVC fixture emitting at 222 nm to directly irradiate an indoor space and then evaluated the doses received upon a manikin. Radiation sensitive film was affixed to the head, nose, lip, and eyes of the manikin, and the 8-hour equivalent exposure dose was determined. Variables examined included manikin height (sitting or standing position), manikin offset from directly below the fixture, tilt of the manikin, the addition of glasses, the addition of hair, and different anatomical feature sizes.Importantly, at the manikin position with the highest dose to eyes, the average eye dose was only 5.8% of the maximum directly measured dose. These results provide the first experimental analysis of possible exposure doses a human would experience from an indoor far-UVC installation.

222 nm Far‐UVC from filtered Krypton‐Chloride excimer lamps does not cause eye irritation when deployed in a simulated office environment

“…However, the variability in recorded measurements was very large, including several measurements where the eye received no UV dose despite significant exposure on the top of the head. 28 Similar variability was observed in a study by First et al, 29 which found variation in participant eye dose of between 3% and 37% compared to a calculated dose. We can, therefore, conclude that while we do not know the exact eye exposures of our participants, it is unlikely that eye exposure will have been higher than the recorded top Individual data points are plotted on the graphs along with the mean number of CFU (column).…”

“…Duncan et al demonstrated in a mannequin study that the eye received, on average, 5.8% of the dose measured from the top of the head. However, the variability in recorded measurements was very large, including several measurements where the eye received no UV dose despite significant exposure on the top of the head 28 . Similar variability was observed in a study by First et al, 29 which found variation in participant eye dose of between 3% and 37% compared to a calculated dose.…”

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

“…(2015) . The AMS SOA concentration was corrected for differences from the default AMS OA relative ionization efficiency (RIE, 1.4) and collection efficiency (CE, 1) (RIE*CE of 1.4) by calibrating the AMS to the measured SMPS SOA mass concentration (using a single factor determined from a linear regression). , This was necessary since organic RIE and CE can vary by as much as factors of 2-3 for chamber-generated SOA and standards. ,, The condensational sink (CS) was calculated from particle size distribution measured by the SMPS per eq CS = 2 π normalD ∑ normali β i d i N i where d i , N i , and β i are the diameter, the number concentration, and the Fuchs–Sutugin correction factor of the particles in the i th size bin, respectively, and D is the diffusion coefficient of the condensable organic gases (assumed to be 7x10 –6 m 2 s –1 ).…”

“…47,48 This was necessary since organic RIE and CE can vary by as much as factors of 2-3 for chamber-generated SOA and standards. 33,42,43 The condensational sink (CS) was calculated from particle size distribution measured by the SMPS per eq 1. 49…”

Far‐UVC Light at 222 nm is Showing Significant Potential to Safely and Efficiently Inactivate Airborne Pathogens in Occupied Indoor Locations

“…Compared with skin studies, there have been comparatively fewer studies of ocular safety after far-UVC exposure. In part, this may be because in the expected geometry of overhead far-UVC lighting, the eye dose to a room occupant is typically only a few percent of the maximum skin dose (19). Extensive studies in rat eyes by Kaidzu et al (17) concluded that the minimum far-UVC dose to induce corneal damage was far larger than the recommended regulatory limits (see below).…”