Cooling system had been installed for all metropolitan high schools in 2008 to improve indoor thermal condition and to increase learning efficiency of students. On the other hand IAQ problem may occur if windows are closed and mechanical ventilation is not operated. It is reported that low indoor humidity activates influenza virus. In this paper, indoor CO2 concentration and humidity are discussed on the basis of measured data in classrooms of high school. Furthermore, CFD simulation was conducted to study appropriate HVAC system to prevent influenza infection.
