Firstly, to renew the indoor air polluted by living living processes with fresh air outside in order to maintain the cleanliness of the indoor air to a certain minimum standard level.

Secondly, to increase heat dissipation the body prevent discomfort caused by skin moisture, this type of ventilation can be called thermal comfort ventilation.

Thirdly, when the indoor air temperature is higher than the outdoor air temperature, the building components are cooled down, this type of ventilation is called cooling ventilation of the building.