Abstract : One of the most common pollutants in the air is cigarette smoke. Cigarette smoke does not only affect the health of active smokers but also for passive smokers. The fact that passive smokers are people around active smokers who are exposed to volatile compounds from the smoke of burning tobacco products and the smoke exhaled by the smoker. The percentage of smoking behavior in the house continues to increase so that in May 2022 it was recorded that 85% of family members with babies and toddlers smoked in the house. Of the 29 Community Health Centers in Musi Banyuasin Regency, it is recorded that in the Working Area of the Balai Agung Health Center the highest percentage of smoking behavior in homes with babies and toddlers is 86% per May 2022. This study aims to analyze the factors that influence exposure CO in Breastfeeding Mothers (ASI) in the Work Area of the Balai Agung Health Center, Musi Banyuasin Regency. This research is a quantitative research with a case control study design. There is no relationship between mother's age and education level with CO exposure in breastfeeding mothers. There is a significant relationship between CO exposure in breastfeeding mothers and its impact on the quality of breast milk (ASI) due to control of confounding variables such as the number of cigarettes per day, home ventilation, the mother's occupation and the duration of exposure to cigarette smoke per day.