Improved method for UV lamps irradiance characterization and life-cycle assessment for in-duct microbial inactivation

Accurate characterization of ultraviolet (UV) irradiance is essential for the effective design and evaluation of in-duct air disinfection systems. This study aims to develop a novel angular correction factor to address sensor detection-angle limitations. Experimental irradiance measurements were conducted for 222 nm excimer lamp, 254 nm mercury lamp, 265 nm UVC LED and 365 nm UVA LEDs, and their environmental sensitivity was assessed under varying air temperature, velocity, and relative humidity. The comparative life-cycle assessment evaluated energy, costs, and environmental impacts for achieving a 3-log microbial reduction. Findings show that the correction factor reduced overestimation by up to 30 % near lamp surfaces, with a maximum error (18 %) observed farther from the 254 nm lamp. Model-based scalability from single LED modules to full arrays yielded an average relative error of ±13 %, supporting flexible LED arrangements. The 254 nm lamp output increased by 18 % as air temperature rose (25–35 °C) and decreased nearly to 80 % as velocity increased (0.5–2 m/s). In contrast, the 222 nm lamp and both LED systems showed minimal sensitivity, indicating greater operational stability under dynamic conditions. While LEDs and 222 nm offer their own advantages, they require higher energy and cost to achieve equivalent disinfection. Therefore, under continuous in-duct application, the 254 nm lamp is the most sustainable and cost-effective option among those tested. This study provides a validated, building-scale framework that improves measurement accuracy and supports energy-aware implementation, offering actionable guidance for optimized, sustainable deployment of UVGI in building ventilation systems.