{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,2]],"date-time":"2026-04-02T17:51:56Z","timestamp":1775152316518,"version":"3.50.1"},"reference-count":27,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2026,4,2]],"date-time":"2026-04-02T00:00:00Z","timestamp":1775088000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Panasonic Co., Ltd."}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Microorganisms"],"abstract":"<jats:p>Vaporized free chlorine, primarily present as hypochlorous acid (HOCl), is increasingly used for indoor microbial control; however, virus-dependent susceptibility and its molecular determinants remain unclear. We evaluated virucidal effects under controlled indoor conditions (0\u20139 ppb) against echovirus 30 (E30), influenza A\/H1N1, and human adenovirus type 3 (HAdV3). Infectious titers were quantified by TCID50 assays. Computational fluid dynamics (CFD) simulations and gas-sensor measurements assessed spatial dispersion, and structural analyses examined oxidation-sensitive amino acid residues. Significant reductions in infectivity were observed for E30 (99.0%, p = 0.00727) and influenza A\/H1N1 (99.9%, p = 0.000597), whereas no significant reduction was detected for HAdV3 (p = 0.142). Analyses including all data points without outlier exclusion confirmed the robustness of these findings. CFD indicated uniform dispersion, although spatial heterogeneity within the indoor environment cannot be excluded. These findings suggest that viral susceptibility to vaporized HOCl is associated with residue-level composition and structural context; however, this relationship should be interpreted as correlative rather than causal. Moreover, integration of molecular and structural analyses provides a plausible mechanistic framework, although direct biochemical validation remains necessary. Structural analyses showed lower proportions of oxidation-sensitive residues in adenoviral proteins compared with influenza A hemagglutinin (OR = 0.34\u20130.40, adjusted p &lt; 0.001) and the E30 VP1 intermediate. Residues were clustered in surface-exposed functional domains in susceptible viruses.<\/jats:p>","DOI":"10.3390\/microorganisms14040814","type":"journal-article","created":{"date-parts":[[2026,4,2]],"date-time":"2026-04-02T16:51:02Z","timestamp":1775148662000},"page":"814","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Inactivation of Surface-Associated Viruses in Real Indoor Environments by a Humidification System Generating Vaporized Free Chlorine Components"],"prefix":"10.3390","volume":"14","author":[{"given":"Saki","family":"Kawahata","sequence":"first","affiliation":[{"name":"Panasonic Ecology Systems Co., Ltd., Kasugai 486-8522, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mayumi","family":"Kondo","sequence":"additional","affiliation":[{"name":"Department of Clinical Engineering, Faculty of Medical Science and Technology, Gunma Paz University, Takasaki 370-0006, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Atsushi","family":"Yamada","sequence":"additional","affiliation":[{"name":"Panasonic Ecology Systems Co., Ltd., Kasugai 486-8522, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Naoya","family":"Shimazaki","sequence":"additional","affiliation":[{"name":"Department of Clinical Engineering, Faculty of Medical Science and Technology, Gunma Paz University, Takasaki 370-0006, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Makoto","family":"Saito","sequence":"additional","affiliation":[{"name":"Department of Clinical Engineering, Faculty of Medical Science and Technology, Gunma Paz University, Takasaki 370-0006, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hiroyuki","family":"Tsukagoshi","sequence":"additional","affiliation":[{"name":"Gunma Prefectural Institute of Public Health and Environmental Sciences, Maebashi 371-0052, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Takayoshi","family":"Takano","sequence":"additional","affiliation":[{"name":"Panasonic Ecology Systems Co., Ltd., Kasugai 486-8522, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tetsuyoshi","family":"Yamada","sequence":"additional","affiliation":[{"name":"Panasonic Ecology Systems Co., Ltd., Kasugai 486-8522, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Toshihiro","family":"Takei","sequence":"additional","affiliation":[{"name":"Panasonic Ecology Systems Co., Ltd., Kasugai 486-8522, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Takashi","family":"Nakagawa","sequence":"additional","affiliation":[{"name":"Panasonic Ecology Systems Co., Ltd., Kasugai 486-8522, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Miu","family":"Takada","sequence":"additional","affiliation":[{"name":"Department of Clinical Engineering, Faculty of Medical Science and Technology, Gunma Paz University, Takasaki 370-0006, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Nobuhiro","family":"Saruki","sequence":"additional","affiliation":[{"name":"Gunma Prefectural Institute of Public Health and Environmental Sciences, Maebashi 371-0052, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hirokazu","family":"Kimura","sequence":"additional","affiliation":[{"name":"Department of Clinical Engineering, Faculty of Medical Science and Technology, Gunma Paz University, Takasaki 370-0006, Japan"},{"name":"Department of Health Science, Graduate School of Health Science, Gunma Paz University, Takasaki 370-0006, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,2]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"289","DOI":"10.7879\/siej.22.289","article-title":"Recent Topics on Microbes in Indoor Environment (4) Microbial Contamination and Countermeasures in Work places","volume":"22","author":"Ishimatsu","year":"2019","journal-title":"Indoor Environ."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"113","DOI":"10.1016\/j.clinmicnews.2008.07.001","article-title":"Reservoirs of Pathogens Causing Health Care-Associated Infections in the 21th Century: Is Renewed Attention to Inanimate Surfaces Warranted?","volume":"30","author":"Bartley","year":"2008","journal-title":"Clin. 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