November 13, 2024
Far-UVC: Weighing Disinfection Benefits & Ozone Caution
Strategic placement found to lower ozone risks and boost disinfection performance
Researchers from Harvard University and Pennsylvania State University have published findings in Scientific Reports that explores the effectiveness of far Ultraviolet C (UVC) light in reducing airborne pathogens, while also examining its impact on indoor air quality. Far-UVC operates at a wavelength between 200 and 280 nanometers (nm) that can kill bacteria and viruses in occupied spaces without penetrating human skin or eyes, making it a safer option for disinfection compared to traditional UVC light.
The research, conducted by Seongjun Park and Donghyun Rim, used three-dimensional simulations to evaluate 222nm far-UVC in a small office. The study found that a ceiling-mounted configuration of far-UVC lighting can reduce airborne pathogens by up to 80%, making it particularly effective in enclosed, occupied areas like offices and hospitals. Different lamp positions—such as wall-mounted and stand-alone—showed variations in effectiveness, with ceiling-mounted systems generally delivering the best results.
Ozone Emissions and Health Implications
While far-UVC light effectively sanitizes the air, it also produces ozone (O₃) as a byproduct, which can be a respiratory irritant. The study observed that after one hour of far-UVC operation, ozone levels rose by 4-6 parts per billion (ppb) in the room, with concentrations exceeding 25 ppb near the light source. This could be problematic, particularly in poorly ventilated spaces where ozone can accumulate and impact occupant health.
The study emphasized ventilation as a key factor in managing ozone levels. Increasing ventilation to 4 air changes per hour (ACH) reduced both pathogens and ozone levels by up to 90%. However, higher ventilation could be less effective in areas with high outdoor ozone levels, where increased airflow may inadvertently raise indoor ozone concentrations.
Positioning Matters for Safety and Efficacy
Far-UVC lamp positioning significantly affects disinfection performance and ozone exposure. The study concluded that ceiling-mounted far-UVC lights were most effective at reducing airborne pathogens and keeping high-ozone areas away from occupants. Stand-alone lamps, by contrast, created localized zones of higher ozone near workspaces, potentially increasing exposure risks.
According to Park and Rim, ceiling-mounted systems allow disinfection while minimizing direct ozone exposure. This setup directs germicidal rays from above, effectively sanitizing the air while keeping ozone concentrations lower in occupied zones.
As far-UVC gains attention for disinfection in indoor settings, Park and Rim’s findings provide a balanced view of its benefits and limitations. Far-UVC at 222 nm shows strong potential for pathogen control in occupied spaces, but ozone production remains a consideration. Optimal ventilation and ceiling-mounted positioning may help manage these risks, making far-UVC a viable tool in healthcare and workplace settings. Future research is expected to refine far-UVC applications across different building types to better understand and control its effects on indoor air quality.
