Development of a Fungal Biosensor for Field Verifying the Surface Disinfection of Ultraviolet Germicidal Irradiation Systems for Air Handling Units

Abstract

This study developed a fungal biosensor to verify the germicidal effect of ultraviolet germicidal irradiation (UVGI) systems in the field from a biosensor originally developed to assess indoor climate. A UVC ray was irradiated on the fungal spores of the biosensors at various doses, and the differences in hyphal length after subsequent incubation were observed to verify the susceptibility of the fungal biosensor to C-band ultraviolet (UVC). The results showed reasonable correlations between UVC dosage and hyphal length. These fungal biosensors were thereafter attached to the coil and the drain pan of an air handling unit with a UVGI system installed and exposed to UVC for 1 h to test the effectiveness of the biosensors on the UVGI systems in the field. The hyphal lengths observed after incubation corresponded with UVC doses of 468–1620 J·m−2 at each sampling point as shown in the previous susceptibility experiments. The extended experiments to confirm the susceptibility of the fungal spores showed that the spores were more sensitive to UVC ray than those of the fungal biosensor and had similar susceptibility to the same UVC doses even at different UVC intensities.