Inactivation Effects of Hypochlorous Acid, Chlorine Dioxide, and Ozone on Airborne SARS-CoV-2 and Influenza A Virus

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza A virus are primarily transmitted through droplets or aerosols from patients. The inactivation effects of existing virus control techniques may vary depending on the environmental factors. Therefore, it is important to establish a suitable evaluation system for assessing virus control techniques against airborne viruses for further real-world implementation. This study aimed to assess the inactivating effects of chemical substances on SARS-CoV-2 and influenza A virus in the air using an established evaluation system. A mixture containing SARS-CoV-2 and influenza A virus in diluted saliva was nebulized into the designed 1 m³ chamber, and the virucidal effects of hypochlorous acid, chlorine dioxide, and ozone in the air samples at 23 ± 1 °C with 50 ± 5% relative humidity were determined using the plaque assay. Both viral infectivity titers decreased depending on chemical substance concentration and exposure time. The concentrations of hypochlorous acid, chlorine dioxide, and ozone in the air reached an approximately 2-log reduction of SARS-CoV-2 infectivity titer within 10 min at 0.02, 1.0, and 1.0 ppm, respectively. SARS-CoV-2 persisted in the air even under conditions where the influenza A virus was inactivated below the detection limits. These findings demonstrate that hypochlorous acid, chlorine dioxide, and ozone are effective in inactivating SARS-CoV-2 and influenza A virus in the air.