Comparative performance and environmental evaluation of 222 and 254 nm UV lamps for in-duct air disinfection in building systems.

UV germicidal irradiance has gained significant popularity as a disinfection technology since the COVID-19 pandemic. Challenges remain in accurately characterizing the in-duct irradiance distribution of UVC lamps under varying air parameters, introducing uncertainty in exposure and efficiency estimations. This study experimentally characterizes irradiance of 222 and 254 nm UV lamps in a conduit using a 9-point average method. Irradiance measurements are recorded from five sides at each point, and a correction factor is proposed to account for spectrometer detection angle overlaps. Results indicate that the 254 nm lamp output increases by 18% with an air temperature rise from 25°C to 35°C but decreases by 21% as air velocity rises from 0.5 to 2 m/s. In contrast, the 222 nm lamp shows negligible sensitivity to changes in air temperature or velocity. Relative humidity variations (25%-60%) did not significantly affect either lamp's output. In addition, the 222 nm lamp generates minimal ozone and total volatile organic compounds (TVOCs) during operation in stagnant air. The particle tracking simulation results revealed higher velocity fluctuations in proximity to the installed 222 nm lamp than the 254 nm lamp due to the larger lamp geometries. Experimental UVGI efficacy tests targeting airborne