Should the car air conditioning use internal or external circulation for cooling?

[LaJohn]

For car air conditioning cooling, use internal circulation. After getting in the car, first turn on external circulation for ventilation and heat dissipation, and you can also open the windows and sunroof to speed up heat dissipation. After 3-5 minutes when the interior temperature has basically stabilized, close all windows, turn on the cooling, and switch the air conditioning to internal circulation. Here are some tips for using air conditioning in summer: 1. Avoid running the air conditioning while parked: Sometimes, to relieve fatigue or while waiting, people park by the roadside, close all windows and doors, turn on the air conditioning, and 'enjoy' the comfort brought by the cool air. Some even lie down on the seat and sleep with the air conditioning on. Experts warn that when the car's engine is running, if the gasoline in the cylinders does not burn completely, it can produce high concentrations of carbon monoxide. 2. Try not to use air conditioning at low speeds: Sometimes, to stay cool, people turn on the air conditioning as soon as they get in the car, whether driving at low or high speeds. Using air conditioning at low speeds, especially in traffic jams, forces the engine to run at higher RPMs artificially, which can reduce the lifespan of both the engine and the air conditioning compressor. Therefore, it's best not to use air conditioning at low speeds. 3. Do not keep internal circulation on for long periods: Car owners know there's a 'circulation' button for the air conditioning. Pressing this button causes the air inside the car to circulate internally only. When all windows and doors are closed, the air conditioning cooling efficiency is fully 'absorbed,' saving energy. However, over time, the air inside the car can become increasingly stale, and one might even feel a lack of oxygen.