This report featuring frequently asked questions about germicidal ultraviolet was prepared by the Photobiology Committee of the Illuminating Engineering Society (IES)  in response to the 2020 COVID-19 pandemic, with the specific goal of providing objective and current information on germicidal ultraviolet irradiation (UVGI) as a means of disinfecting air and surfaces. The IES provides this information freely and will update it periodically, as more information becomes available.