NATURAL VENTILATION EFFECT ON CO2 CONCENTRATIONS IN CLASSROOMS, WAKAYAMA UNIVERSITY, JAPAN

Abstract

Using a portable CO2 sensor, the CO2 concentration in a classroom at Wakayama University
was measured and “natural ventilation”, the open door or window effect was evaluated based upon the
number of persons, room size, door or window condition and CO2 concentration. Under no ventilation
condition in the classroom, increase of CO2 concentration was 2,000 to 4,000 ppm after 90 minutes and CO2
production per person per hour due to respiration was 0.005 to 0.015 m³/hour/person during a lecture.
Comparing CO2 concentration under no ventilation condition with under natural ventilation condition, effect
of natural ventilation to reduce CO2 concentration per open space size was calculated. The amount of CO2
gas exchanged outside through doors or windows by natural ventilation was in agreement with the amount of
CO2 gas produced by respiration in the room when sizes of open doors or windows were 2.3 to 12.8 m²
or ratios of total room volumes per open door or window sizes were 40 to 180 m.