Analysis of Indoor CO₂ Changes According to Ventilation Conditions and Occupant Density in Karaoke

Abstract This study investigated changes in indoor carbon dioxide (CO 2 ) concentrations in karaoke rooms in relation to room size, occupancy, and mechanical ventilation operation. Field measurements were conducted in small, medium, and large rooms with occupancies of one to three persons, and CO 2 concentrations and change rates during singing were analyzed. Under Ventilation OFF conditions, the individual CO 2 release rate during singing was estimated, and the relationships of CO 2 change rate with room area and occupant density were examined. Under Ventilation ON conditions, the average CO 2 concentration during the singing period remained below 1,000 ppm in eight of the nine measurement conditions. Under Ventilation OFF conditions, the average CO 2 concentration exceeded 1,000 ppm in five of the nine conditions, and CO 2 concentrations increased in all measurement conditions. Under Ventilation OFF conditions, the CO 2 change rate increased with decreasing room size and increasing occupancy, and the average individual CO 2 release rate during singing was estimated to be 0.272 ± 0.071 L/min·person. The relationship between room area and CO 2 change rate showed an R 2 of 0.4433, whereas occupant density, which reflects both room size and occupancy, showed greater explanatory power with an R 2 of 0.9238. These findings indicate that continuous mechanical ventilation and appropriate occupancy management according to room size are important for controlling indoor CO 2 levels in karaoke rooms. The results can provide a basis for developing ventilation operation and indoor CO 2 management strategies for karaoke rooms.