Stella Jang's song "CO (일산화탄소)" is about the harmful effects of carbon monoxide on the human body and the environment. The lyrics describe how the singer was healthy and did not catch any illnesses before meeting someone who causes them to feel breathless and suffocated. The song emphasizes the importance of clean air and warns against the dangers of pollution. The lyrics describe carbon monoxide as a molecule that is lighter than air, colorless, odorless, and tasteless. The singer pleads with the person to not use up their hemoglobin, which is essential for carrying oxygen, and warns that pollution can cause sickness and even death. In the chorus, the singer asks if the person they are addressing is also affected by carbon monoxide and encourages them to think about how harmful it can be. The song ends with a plea for the person to disappear from the atmosphere and not harm the singer anymore. Overall, "CO (일산화탄소)" is a cautionary tale about the dangers of pollution and the importance of preserving clean air for our health and well-being.