Effects of Germicidal UV Air Disinfection Devices on Indoor Air Quality in an Unoccupied Aged Care Facility

The COVID-19 pandemic has precipitated renewed interest in germicidal ultraviolet (GUV) for indoor air disinfection. However, UV-C radiation from these devices can produce indoor air pollutants including ozone, oxygenated volatile organic compounds (OVOCs), and ultrafine particles. A month-long study of indoor air quality effects of GUV was undertaken in an unoccupied aged care facility in Melbourne, Australia under both mechanical ventilation (∼3 air changes h–1) and natural ventilation (∼1 h–1) conditions. Upper room GUV-254 and whole room GUV-222 devices were tested. GUV-222 produced ∼670 μg/h of ozone resulting in <1 ppb enhancements in indoor ozone. GUV-222 also produced small increases in OVOCs, particularly acetic acid and methanol, that were <1 ppb with mechanical ventilation, and <2 ppb with natural ventilation. Small acetaldehyde enhancements (∼0.1 ppb) were associated with GUV-254. GUV was not associated with changes in indoor particles. GUV-222 and -254 initiated OVOC enhancements were insensitive to indoor ozone but exhibited strong temperature and humidity sensitivities, suggesting UV-initiated surface chemistry rather than gas phase chemistry as the key driver of GUV OVOC enhancements. Overall, ventilation and changes in outdoor pollutants had substantial effects, while GUV produced small but measurable effects on indoor air quality in a real-world urban setting.