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Microorganisms
Volume 13
Issue 9
10.3390/microorganisms13092053
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This is an early access version, the complete PDF, HTML, and XML versions will be available soon.
Article

Control of Airborne and Surface Microorganisms in Real Indoor Environments Using an Integrated System of Vaporized Free Chlorine Components and Filtration

by
Saki Kawahata
1,†,
Mayumi Kondo
2,†,
Atsushi Yamada
1,
Naoya Shimazaki
2,
Makoto Saito
2,
Takayoshi Takano
1,
Tetsuyoshi Yamada
1,
Yoshinobu Shimayama
1,
Shunsuke Matsuoka
1 and
Hirokazu Kimura
2,3,4,*
1
Panasonic Ecology Systems Co., Ltd., Kasugai 486-8522, Japan
2
Department of Clinical Engineering, Faculty of Medical Science and Technology, Gunma Paz University, Takasaki 370-0006, Japan
3
Advanced Medical Science Research Center/Research Facility Administration Office, Gunma Paz University Research Institute, Takasaki 370-0006, Japan
4
Department of Health Science, Gunma Paz University Graduate School of Health Science, Takasaki 370-0006, Japan
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Microorganisms 2025, 13(9), 2053; https://doi.org/10.3390/microorganisms13092053
Submission received: 28 July 2025 / Revised: 29 August 2025 / Accepted: 2 September 2025 / Published: 3 September 2025
(This article belongs to the Special Issue Novel Disinfectants and Antiviral Agents)
Versions Notes

Abstract

Airborne and surface-residing microorganisms in indoor environments pose potential risks for infectious disease transmission. To address this issue, we developed a composite device combining a generator of vaporized free chlorine components with a fine particle removal filter. Field tests were conducted in occupied university classrooms to evaluate the device’s efficacy in reducing airborne bacterial loads. Airborne bacteria were sampled under three operational conditions [Electrolyzed (+)/Filter (+), Electrolyzed (−)/Filter (+), and Electrolyzed (−)/Filter (−)]. Significant reductions in bacterial counts were observed in the Electrolyzed (+)/Filter (+) condition, with a residual rate of 14.5% after 2.25 h (p = 0.00001). Additionally, surface contact tests demonstrated that vaporized free chlorine components, primarily consisting of hypochlorous acid (HOCl), reduced viable counts of E. coli, P. aeruginosa, and S. aureus by 59.0–99.7% even at a distance of 8.0 m. The concentrations of vaporized free chlorine components during operation remained within safe exposure limits (0–19 ppb), consistent with the effective range reported in prior literature (10–50 ppb). Computational fluid dynamics simulations confirmed the diffusion of vaporized free chlorine components throughout the room, including distant sampling points. These findings suggest the combined use of a vaporized free chlorine generator and a particulate filter effectively reduces microbial contamination in indoor environments, providing a promising approach for infection control in residential and public settings.
Keywords: infection control; airborne/surface microorganisms; real indoor environment; integrated vaporized free chlorine components and filtration system; HOCl; hypochlorous acid infection control; airborne/surface microorganisms; real indoor environment; integrated vaporized free chlorine components and filtration system; HOCl; hypochlorous acid

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MDPI and ACS Style

Kawahata, S.; Kondo, M.; Yamada, A.; Shimazaki, N.; Saito, M.; Takano, T.; Yamada, T.; Shimayama, Y.; Matsuoka, S.; Kimura, H. Control of Airborne and Surface Microorganisms in Real Indoor Environments Using an Integrated System of Vaporized Free Chlorine Components and Filtration. Microorganisms 2025, 13, 2053. https://doi.org/10.3390/microorganisms13092053

AMA Style

Kawahata S, Kondo M, Yamada A, Shimazaki N, Saito M, Takano T, Yamada T, Shimayama Y, Matsuoka S, Kimura H. Control of Airborne and Surface Microorganisms in Real Indoor Environments Using an Integrated System of Vaporized Free Chlorine Components and Filtration. Microorganisms. 2025; 13(9):2053. https://doi.org/10.3390/microorganisms13092053

Chicago/Turabian Style

Kawahata, Saki, Mayumi Kondo, Atsushi Yamada, Naoya Shimazaki, Makoto Saito, Takayoshi Takano, Tetsuyoshi Yamada, Yoshinobu Shimayama, Shunsuke Matsuoka, and Hirokazu Kimura. 2025. "Control of Airborne and Surface Microorganisms in Real Indoor Environments Using an Integrated System of Vaporized Free Chlorine Components and Filtration" Microorganisms 13, no. 9: 2053. https://doi.org/10.3390/microorganisms13092053

APA Style

Kawahata, S., Kondo, M., Yamada, A., Shimazaki, N., Saito, M., Takano, T., Yamada, T., Shimayama, Y., Matsuoka, S., & Kimura, H. (2025). Control of Airborne and Surface Microorganisms in Real Indoor Environments Using an Integrated System of Vaporized Free Chlorine Components and Filtration. Microorganisms, 13(9), 2053. https://doi.org/10.3390/microorganisms13092053

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