A Drexel Engineering team has translated complex computer models of UV air disinfection into simple tools that architects and engineers can use in schools, offices and clinics.
Led by Bryan E. Cummings, PhD, with Charles N. Haas, PhD; L. James Lo, PhD; Christopher M. Sales, PhD; and Michael S. Waring, PhD, in the Department of Civil, Architectural and Environmental Engineering, the study appears in Building and Environment and addresses how to plan whole-room systems that inactivate airborne pathogens while people are present.
The study centers around 222 nanometer far-UVC, a type of ultraviolet light with germicidal properties that is often used in ceiling-mounted fixtures to disinfect air and surfaces in occupied spaces. Using computational fluid dynamics, the researchers ran hundreds of virtual room experiments that varied room size, air flow, fixture layout, lamp power and how susceptible different pathogens are to this light. They then distilled the results into quick-running models, free to use on a web-based application, that estimate how much “clean air” a far-UVC system adds, expressed as equivalent air changes per hour, or eACH.
“Design practitioners can use one of two reduced-order models as a tool for system design,” Cummings, a former Drexel research scientist, currently a building environmental science engineer with Harris Design Studio in Virginia. “The first is a compact equation of UV power density and a pathogen’s susceptibility that predicts eACH. The second is a machine learning model that improves accuracy and predicts risk reductions. These approaches offer engineers simple methods for designing systems to meet quantifiable performance targets at quantifiable confidence levels.”
One practical takeaway stands out for designers. The simulations show that, all else equal, using more low-power fixtures across a room outperforms using only a few high-power fixtures. Spreading out the light increases the chance that tiny aerosols pass through irradiated regions. The study also explains eACH in plain terms so decision makers can compare UV disinfection directly to ventilation upgrades when planning budgets and schedules.
The paper balances performance with safety and operations. The authors note that far-UVC systems can create small amounts of ozone and other chemical byproducts indoors, which should be managed with adequate ventilation and thoughtful placement. They frame deployment as a risk-management decision that considers infection risk, community vulnerability, chemistry and energy use alongside other controls.
“In practice, widespread use in public settings might be justified during periods of high community infection or the emergence of a novel respiratory threat,” Haas explained. “During normal conditions, healthcare spaces may be good candidates for continuous use because the baseline risk is higher.”
By converting hundreds of physics-based simulations into usable rules of thumb, the Drexel team provides a bridge from research to practice. The result is a set of design-ready tools that can help building owners, engineers and facility managers plan UV systems that are effective, safer to operate and suited to the spaces where they are needed most.
Read the full paper: https://www.sciencedirect.com/science/article/pii/S0360132325008157
Access the web-based design tools: https://research.coe.drexel.edu/caee/balvi/