Experimental analysis of co₂ concentration changes in an apartment using a residential heat recovery ventilator

Korean law requires at least three levels of control for apartment ventilation systems, including 0.5 air change per hour (ACH). When this law was enacted, it was believed that a 0.5 ACH air flow rate would be sufficient for apartments following building completion. However, ventilation systems cause different air qualities in each space within a unit, depending on infiltration rate and number of occupants. In addition, the current ventilation rate standard is based on an apartment unit’s total area, assuming that all room doors are open. In this study, changes in CO₂ concentration were experimentally analyzed based on the number of occupants and various ventilation frequencies with closed doors to analyze air quality differences among rooms in a typical 85 m² apartment unit in Korea. When the 0.5 ACH ventilation was performed, maintaining 1000 ppm or less was difficult if four people stayed for more than two hours in the living room or two people stayed for more than one hour in the bedroom with closed doors. Our results indicate that it is challenging to maintain a CO₂ concentration of 1000 ppm when doors are closed as standards are calculated based on a unit’s total area. Therefore, ventilation systems should be required to provide different air volumes for each room.