In general, windows can be opened for ventilation on the lower floors of the neighborhood. Ventilation dilutes the concentration of virus and enhances air flow, which is the least expensive and most efficient way to prevent novel coronavirus infection. It is recommended that windows be opened three times a day for 20-30 minutes each time, provided that they are kept warm. However, if there are isolated patients in the upstairs, downstairs or opposite windows, you need to be flexible with the window opening time, such as staggered ventilation or not to open the window immediately adjacent to the patient, if the building is densely populated and surrounded by infected patients, it is also not recommended to open windows frequently for ventilation.