Why do you close the doors and windows when you sleep at night?

In fact, closing the door when we sleep is nothing more than quiet, energy saving, privacy and other issues, but we will find that when we sleep for one night and open the window the next morning, we will feel the outdoor air is very fresh. No matter what is outside, even if it is heavy smog, we will feel that the outdoor air is fresher than the indoor air. In fact, our human body is also a kind of metabolism during sleep, which will produce a large number of chemicals, including more than 500 kinds discharged from the respiratory tract. Two people sleep in a room with closed doors and windows of 10 square meter. After two hours of testing, it will be found that the carbon dioxide in the room has increased by about three times, and the solubility of carbon dioxide has increased by more than six times after sleeping all night. The longer the doors and windows are closed, the higher the concentration of indoor pollutants such as carbon dioxide, and people will feel depressed, stuffy, sore throat, dry mouth, stuffy nose and other problems. In fact, when the air is fresh, ventilation can be achieved by opening the window. But when the smog outside is serious, or when it is a few degrees below zero in winter, how many people are willing to open the window and ventilate as human flesh vacuum cleaners? In cities, the pollution of outside air and noise, as well as the cold wind in winter, make people close doors and windows, stay in unventilated rooms for a long time, and can't breathe fresh air.