TPS 664: Climate change: temperature effects 2, Exhibition Hall, Ground floor, August 27, 2019, 3:00 PM - 4:30 PM Aim: The purpose of this study is to investigate the health impact of air conditioning use during the 2018 heatwave in South Korea, which is the warmest in Korean weather observation history. Methods: Participants in this study were 1,000 adults aged >18 who were recruited from across Korea. Participants were asked about the symptoms of various diseases, air-conditioningitis, food poisoning, and whether they had any absences, lateness, or canceling appointments during the heatwave. About their air conditioning use, we questioned whether air conditioning was used in main living space excluding home, had air conditioning at home, and could not use air conditioning because of the electric charges when air conditioning is necessary. Association between air conditioning use and health impacts during the heatwave was analyzed by multiple logistic regression model. Potential confounding factors included age, sex, residential area, occupation, type of house, number of family members, prevalence of chronic diseases, and monthly household income. Results: When air conditioner was not operated in main living space excluding home, odds ratio (OR) of experiencing symptoms related to cardiovascular diseases and neurological diseases was 8.53, and 2.02, respectively. In the absence of air conditioner at home, OR of experiencing symptoms related to neurological diseases and canceling appointments was 1.64, and 3.43, respectively. When electric charges limit air conditioning use where it is necessary, OR of experiencing symptoms of all diseases, skin diseases, digestive diseases, kidney and urinary diseases, nervous system diseases, mental diseases, sleep disorders, food poisoning, lateness, and canceling appointments was 1.76, 1.92, 1.65, 4.74, 1.52, 1.57, and 1.63, respectively. Conclusion: When air conditioner cannot be operated in home or main living space, it has a negative health impact during heatwave. And if electric charges limit air conditioning use when it is necessary, the situation also has a negative impact on health.