TOKYO, December 15, 2025 - Mitsubishi Electric Corporation (TOKYO: 6503) announced today that in collaboration with Professor Toshiaki Kamachi and colleagues from the School of Life Science and Technology at Institute of Science Tokyo (Science Tokyo) they have achieved the world’s first¹ mechanism for elucidating the combined use of negative ions to enhance the oxidative action of ozone. In their joint study, they discovered that dissolving negative ions in the moisture surrounding viruses and other microorganisms lowers the pH due to nitrate-containing components derived from the negative ions, which in turn enhances the oxidative action of ozone in the moisture, enabling a strong reduction of viruses and bacteria even at low ozone concentrations. Mitsubishi Electric confirmed the reduction of bacteria and odors in low ozone concentrations of 50 parts per billion (ppb)² in addition to specific viruses reported previously.³

Buildings are becoming more airtight and better insulated, raising concerns about inadequate indoor ventilation and unhygienic conditions. Ozone’s oxidative action has traditionally been used to maintain indoor hygiene, but ozone alone has faced challenges in terms of the durability and stability of its sanitizing effects. It is also known that ozone’s reduction of viruses and bacteria increases when used with negative ions and varies with pH. However, the specific chemical species of the negative ions and their pH-controlling effects had not been clarified.

Using Mitsubishi Electric’s established technologies to evaluate the reduction of viruses, bacteria and odors, together with Science Tokyo’s analytical and identification capabilities for discharge-generated reactive species,⁴ the two organizations clarified how negative ions control pH in aqueous films. They also elucidated the mechanism by which the combined use of negative ions enhances ozone’s oxidative action, and additionally confirmed that adherence of Escherichia coli and pink slime yeast to test specimens in wet areas was reduced by 99% within one hour, and that sweat and damp-clothing odors were reduced by at least one unit of odor intensity within one hour.⁵

Details will be presented at the Pacifichem⁶ 2025 international conference in Honolulu, Hawaii from December 15 to 20.

Going forward, Mitsubishi Electric will continue to develop innovative technologies for safer and more enjoyable indoor environments.