MECHANICAL VENTILATION IMPROVEMENTS FOR AEROSOL INFECTION CONTROL IN CHILDCARE FACILITIES (PART 1) : EVALUATION OF VENTILATION EFFECTS USING CO<sub>2</sub> TRACER GAS

The ventilation rates for childcare facilities that are already built and in operation comply with the Japanese Building Standards Act (2003), which includes an air exchange standard of 0.3 per hour to prevent sick house syndrome. However, these rates fall below the ventilation levels recommended by COVID-19 precaution protocols, raising concerns about infection risks. This study demonstrates that upgrading a mechanical ventilation system to operate at approximately 20 m3/h per person effectively improved indoor CO2 levels. Additionally, the upgraded system reduced stagnant air and provided more uniform air distribution. Therefore, ventilation design should prioritize per-person rates over current standards.