An experiment demonstrated that in a 10-square-meter room with three people and closed windows, after three hours, the temperature rises while carbon dioxide levels, bacteria, and dust accumulate. Prolonged exposure to such air may cause mild symptoms like headaches, dizziness, fatigue, and poor sleep quality. In severe cases, it can worsen or trigger conditions such as coronary heart disease, chronic bronchitis, and COPD, posing significant health risks. Learn more below.