Effect of chlorine dioxide gas of extremely low concentration on absenteeism of schoolchildren

Gas-generating devices of chlorine dioxide (ClO2) are used as deodorant of rooms. We happened to use a commercial tabletop deodorant canister that releases extremely low-concentration ClO2 gas in a school classroom as deodorant. We found retrospectively and unexpectedly that during a period of 38 consecutive school days the rate of school children absent from the school was markedly lower (1.5%) in a classroom where the ClO2 device was placed than that (4.0%) in a classroom where it was not placed. The percentages of absenteeism between these classrooms (1.5% vs. 4.0%) were significantly (p < 0.00001) different. The predominant causes of absenteeism during the period were common cold and influenza. Judging from the known virucidal activity of ClO2, our unexpected finding in the school classrooms strongly suggests the usefulness of extremely low-concentration ClO2 gas to prevent respiratory viral diseases in semi-closed areas, such as theaters, hospitals and aircraft, without necessitating evacuation.