Far-UVC (222 nm) disinfection performance in residential spaces: Experimental study on Bacillus subtilis contamination

Abstract

Ultraviolet germicidal irradiation (UVGI) with a 254 nm wavelength is widely used for sterilization due to its high efficacy in microbial inactivation. However, its application in daily environments is hindered by potential risks to skin and eye health upon direct exposure. Recently, far-UVC light at a safer wavelength of 222 nm has shown promise in maintaining human safety while effectively inactivating microorganisms. This study evaluates the disinfection performance of far-UVC (222 nm) in typical residential settings, specifically in high-touch areas such as shoe racks and bathrooms, with varied irradiation distances and times. Targeting Bacillus subtilis, a resilient model organism, we observed significant microbial reductions: a 91 % reduction on shoe racks within 5 min and a 50 % reduction in bathrooms over 4 h Calculated sterilization coefficients (k values) for B. subtilis on shoe racks and in bathrooms were 0.196 m²/J (R² = 0.98) and 0.202 m²/J (R² = 0.81), respectively, closely matching the manufacturer's specification of 0.1956 m²/J. Far-UVC also demonstrated compliance with IEC 62471 safety standards, supporting its use in daily residential environments. These findings support the evidence for far-UVC's efficacy and safety in controlling microbial contamination in residential spaces, offering practical solutions for enhanced hygiene management in high-contact areas within households.