What is the difference between external circulation and internal circulation in a vehicle?

[VanDiana]

The difference between external circulation and internal circulation in a vehicle is: 1. Different effects: External circulation ensures air flow between the inside and outside of the vehicle, preventing excessive carbon dioxide concentration; Internal circulation air becomes stale over time, with decreased oxygen levels. 2. Different air flow methods: External circulation heats or cools air from outside the vehicle before sending it inside, facilitating gas exchange between inside and outside; Internal circulation recirculates air within the vehicle after heating or cooling it. When using air conditioning, internal circulation is used to quickly lower the interior temperature by blocking the continuous inflow of hot air from outside. However, when driving on highways or in sparsely populated areas, occasionally switching to external circulation helps replenish fresh air. In summer, turning on internal circulation while using the air conditioner prevents cold air from escaping and hot air from entering, improving cooling efficiency and reducing the load on the air conditioning system.