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

Far-UVC radiation, defined in this paper as ultraviolet (UV) radiation with wavelengths from 200 to 235 nm, is a promising tool to help prevent the spread of disease. The unique advantage of far-UVC technology over traditional UV 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-h 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.