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.

Evaluation of Single-Pass Disinfection Performance of Far-UVC Light on Airborne Microorganisms in Duct Flows

“…Currently, there are regulatory exposure limits for 222 nm far-UVC irradiation. For example, ACGIH (American Conference of Governmental and Industrial Hygienists) 8 h threshold limit values for 222 nm far-UVC are around 160 mJ/cm 2 for the eyes and 480 mJ/cm 2 for skin, which are much higher than the limit for 254 nm UV (6 mJ/cm 2 ). ,, However, the health issues related to exposure to 222 nm far-UVC are not concerns for in-duct or in-channel applications.…”

“…For example, ACGIH (American Conference of Governmental and Industrial Hygienists) 8 h threshold limit values for 222 nm far-UVC are around 160 mJ/cm 2 for the eyes and 480 mJ/cm 2 for skin, which are much higher than the limit for 254 nm UV (6 mJ/ cm 2 ). 43,45,46 Another potential health risk of using gas discharge lamp technology for UVC irradiation is the generation of the byproduct ozone. 47 There is a concern that this powerful oxidant, through the ductwork system, will be transported to indoor environments.…”

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

“…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 ., which found variation in participant eye dose of between 3% and 37% compared to a calculated dose(29).…”