: My mother has a habit to close all the windows and doors when she goes to sleep. She always thinks she's weak. If she sleeps in a room with open window for just one night, she is going to catch a cold. Me, on the contrary, can't stay with any places without windows. We need fresh air even when we're asleep, right?
A: Ideally people should stay in a room with enough air. If a person stays in a place with poor ventilation for a long long time, it's possible that there's no enough oxygen in the room, or there are high level of germs in the air. But that can't happen in just one night. As long as the room has enough space, not too small, and you open the windows in the day, the air quality in the room will be okay over night. I do agree with your mother to keep warm at night, although I like to keep the windows open a bit, I don't think it's bad to keep them shut.