When is the best time to open the window in Beijing?

Now at the turn of spring and summer, it is best to open the window for ventilation from 2 pm to 4 pm.

Because Beijing is at the turn of spring and summer from two to four in the afternoon. The air outside is cool, dry and refreshing, which can take away the polluted air and moisture in the house. Moreover, there are relatively few dust and bacteria in the air during this time.