Effects of environmental factors, measurement and modeling for germicidal efficiency of in-duct ultraviolet germicidal irradiation system

In-duct ultraviolet germicidal irradiation (UVGI) systems effectively decontaminate airborne microorganisms that are present in duct air. In this study, the main objectives were to determine the effects of temperature, relative humidity (RH), air velocity, and measurement on the germicidal efficiency of in-duct UVGI and to analyze three germicidal kinetic models. Staphylococcus albus and Escherichia coli were selected as the test bacteria. The maximum UV disinfection efficacy was observed in the temperature range of 26–28 °C and RH range of 30–40 %. The germicidal efficiency of the in-duct UVGI was negatively corelated with air velocity. When the UV lamps were arranged either parallel or vertical to the airflow, there were no obvious differences in-duct UVGI germicidal efficiency. In addition, three mathematical prediction models (C-W model, C-S model, Hom model) were chosen to predict the efficacy of in-duct UVGI in specific applications. The C-S model was fitted to predict the efficacy of E. coli, and the Hom model was fitted to predict that of Staphylococcus albus.