Abstract
The antiviral and antibacterial properties of ozone gas have been utilised for air and on-site disinfection. However, excess ozone gas exposure is toxic to humans, necessitating the monitoring of exposure levels. While this has been achieved using ozone indicators, determining exposure levels at intermediate time points during exposure remains challenging owing to the current ones being capable of measuring exposure only at endpoints. Shifts in the endpoint are also difficult as the coverage ranges of the indicators are dependent on a single colour dye. The indicator that covers a wide range is desirable to treat various pathogenic microorganisms. The aim of this study was to develop a two-colour ozone indicator with a broad coverage range that does not compromise the performance of the individual dyes. Exposure levels were indicated by visible changes in colour density and phase, aiding the measurement of exposure at the endpoints and during the exposure period, thereby maintaining better safety profiles for exposed individuals. Additionally, a theoretical approach for the development of two-colour indicators has been described.