Researchers have unveiled a groundbreaking solution for controlling airborne transmission of pathogens – the far-UVC lighting system. This innovative technology utilizes ultraviolet light at a wavelength of 222 nanometers (nm) to effectively inactivate airborne microbes, including the SARS-CoV-2 virus. Unlike traditional UVC lamps, far-UVC light is safe for human exposure, making it a promising tool for disinfecting indoor environments. In this study, the researchers examined the impact of lamp positioning and ventilation conditions on the performance of far-UVC systems in an office setting, shedding light on the complex interplay between airborne pathogen control and the formation of secondary contaminants.
Unlocking the Power of Far-UVC Lamps
The far-UVC system has emerged as a cutting-edge solution for combating the spread of airborne pathogens. Unlike the traditional 254 nm UVC, far-UVC light at 222 nm has been shown to effectively inactivate a wide range of microorganisms, including SARS-CoV-2, the virus responsible for the COVID-19 pandemic. The key advantage of far-UVC is its minimal impact on human tissues, making it a safer option for comprehensive indoor disinfection.
However, the researchers highlighted a critical concern – the potential for far-UVC lamps to generate ozone (O3), a harmful secondary contaminant. The photolysis of oxygen (O2) by the 175-242 nm wavelength range inherent to the far-UVC system can lead to the formation of ozone, which poses its own health risks and can initiate indoor chemical reactions, resulting in the production of other air pollutants.
Exploring the Impact of Lamp Positioning and Ventilation
To address these complex interactions, the researchers conducted a comprehensive computational fluid dynamics (CFD) study to investigate the impact of far-UVC lamp positioning and ventilation conditions on both the disinfection of airborne pathogens and the formation of secondary contaminants in a small office environment.
The study examined six different far-UVC lamp positions, including ceiling-mounted, wall-mounted, and stand-alone configurations, along with four distinct ventilation conditions ranging from the minimum requirement of 0.7 air changes per hour (ACH) to a recommended rate of 4 ACH.
The key findings of the study reveal that:
1. Ceiling-mounted far-UVC lamps are the most effective: This configuration consistently demonstrated the lowest airborne pathogen concentrations, reducing human exposure by up to 80% compared to scenarios without far-UVC.
2. Ventilation plays a crucial role: Increasing the ventilation rate from 0.7 ACH to 4 ACH can reduce airborne pathogen and secondary contaminant concentrations by up to 90%. However, higher ventilation rates can also lead to elevated indoor ozone levels, especially in areas with high outdoor ozone concentrations.
3. Ozone generation is a concern: The far-UVC system operation increased the ozone concentration in the breathing zone by 4-6 parts per billion (ppb) after one hour of use. Additionally, a high-concentration ozone zone (> 25 ppb) was observed near the far-UVC lamp, highlighting the importance of positioning the lamp away from occupants.
Implications and Future Directions
The findings from this study suggest that the ceiling-mounted far-UVC configuration may be the most effective and safer option for controlling airborne pathogens in indoor environments. However, the researchers emphasize the critical role of ventilation in mitigating the formation of secondary contaminants, such as ozone.
As the far-UVC technology continues to evolve, further research is needed to address the limitations of this study, including the consideration of particle size distribution, the effects of evaporation, and the comprehensive modeling of chemical reactions. Nonetheless, this research provides valuable insights into the complex interplay between far-UVC lamp positioning, ventilation, and indoor air quality, paving the way for the development of safer and more effective disinfection solutions for public spaces.
Author credit: This article is based on research by Seongjun Park, Donghyun Rim.
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