Indoor air pollutant levels can be affected by both internal and external factors. However, most epidemiological studies have focused on outdoor air pollution. Here, we aimed to provide nationally representative data on residential air quality in Korea and to identify the determinants of residential air quality. We conducted an indoor air quality study in 1182 households nationwide from July 2020 to August 2021 based on the Korean National Health and Nutrition Examination Survey. In addition to the questionnaire conducted with occupants, we measured indoor PM