Plate heat exchangers are used in the ventilation system of office buildings, which can introduce fresh air that has undergone heat exchange treatment when the outdoor temperature is suitable in spring and autumn, achieving natural ventilation and reducing the frequency of air conditioning use; In winter and summer, preheat or pre cool the fresh air to reduce air conditioning load and create a comfortable office environment. Moreover, plate heat exchangers can also be combined with fresh air purification devices to filter pollutants in outdoor air, providing employees with healthy and clean air and improving work efficiency.