Japan has been well on the way to an aging society and entered a super-aged society at 21.5 percent aging rate in 2007, and the facility demand for the elderly is increasing rapidly. The elderly need suitable environmental hygiene management from a viewpoint of protection against infectious diseases, since the autonomous control ability, recuperative and immunological power of them is poorer than healthy people. However, there is not a law concerning indoor environment in those facilities and still unknown part is large in the actual situation.
This study conducted the winter survey on five facilities for two months to clarify the actual condition and the management of indoor environment such as air temperature, relative humidity and CO₂ concentration (i.e. ventilation situation).
As a result, air temperature and CO₂ concentration had been generally well managed. Meanwhile, relative humidity in all facilities was below 40%RH which is recognized as a winter lowest standard. Moreover, CO₂ concentrations showed that there was a significant difference in the amount of ventilation depending on facilities. Despite efforts of facilities for humidification, it was clear that they could not meet 40%RH of commonly accepted minimum standard for relative humidity in winter. Consequently it suggested that there was a problem in knowledge and recognition of facility managers for humidity and humidification, and the low humidity might come from not poor humidification but increase of outdoor air intake for ventilation. Ventilation rates estimated from the measured data and the theoretical amount of CO₂ and moisture emitted from human body showed also that the humidification amount was not sufficient with respect to ventilation amount.

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The application of ozone as decontamination and disinfection agent has been attracting attention for a long time, due to the strong oxidizability and low running cost. The high reactivity of ozone against microorganisms in water is widely recognized. However, the decontamination, disinfection and inactivation effects of gaseous ozone have been studied especially in view point of controlling indoor environmental quality, concrete application procedure of gaseous ozone in indoor air quality control have not yet determined. In this study, the potential of using gaseous ozone for decontamination of indoor environment was discussed. This paper summarized previous research concerning the control of microorganisms by gaseous ozone and the efficacy of gaseous ozone against microorganisms. Furthermore, the issues of applying gaseous ozone for decontamination in indoor environment were summarized. In addition, the numerical and mathematical modeling of decontamination effects of gaseous ozone on microorganism was also discussed.

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