Systematical Investigations on Disinfection Effectiveness of Far-UVC (222 nm) irradiation: From Laboratory Study to Field Tests

Ruijie Xie¹, Gabriel Y. K. Tse¹, Linda C.L. Man², Anthony L.H. Cheung², Dickson T. C. Wong², Edmond H. M. Lam², Haibao Huang³ and Dennis Y.C. Leung^1,

¹Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077, China

²Electrical and Mechanical Services Department, HKSAR Government, Hong Kong, 999077, China

³School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, China

Cite this paper:
Ruijie Xie, Gabriel Y. K. Tse, Linda C.L. Man, Anthony L.H. Cheung, Dickson T. C. Wong, Edmond H. M. Lam, Haibao Huang and Dennis Y.C. Leung. Systematical Investigations on Disinfection Effectiveness of Far-UVC (222 nm) irradiation: From Laboratory Study to Field Tests. Journal of Applied & Environmental Microbiology. 2022; 10(1):17-34. doi: 10.12691/jaem-10-1-3

Abstract

The spread of pathogenic microorganisms in public spaces poses a great threat to human health. Far-UVC irradiation is regarded as an efficient method for inactivating most pathogenic microorganisms. Nevertheless, most of the studies on it have been done in laboratory, and there is still little knowledge about the disinfection effectiveness of far-UVC irradiation in real life. Here, systematic investigations were conducted to shed light on the disinfection effectiveness of far-UVC irradiation with laboratory studies and field tests in a real operating public lift cabin. The results of the laboratory study demonstrated that far-UVC irradiation can markedly promote the inactivation of the selected 7 types of microorganisms (including bacteria, viruses and fungus species) on steel surface compared to that on the glass surface, due to the synergistic effect of direct and reflected far-UVC light. This improvement was identified in the field test by employing the far-UVC device for disinfecting the surfaces of the lift cabin which are mostly made of stainless steel. Furthermore, the long-term field test of about 4 months also suggested that both environmental temperature and relative humidity (RH) affect the far-UVC disinfection effectiveness, where the best inactivation efficiency (99.9%) on the surface of lift button and handrail was achieved in the environmental temperature range of 23.5-25.5°C and the RH range of 60-70% at a low UVC dose of 5.2 mJ/cm². In addition, >99.9% of airborne bacteria were inactivated in a chamber at a far-UVC dose of 15 mJ/cm², showing a better performance of far-UVC for air disinfection compared to other technologies. This study systematically investigates the performance of far-UVC irradiation for surface and air disinfection in an actual environment, which provides helpful guidance for controlling the spread of pathogenic microorganisms in public spaces, especially in the ongoing COVID-19 pandemic.

Keywords:
far-UVC surface contamination airborne bacteria disinfection public space

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