Should the car air conditioning be set to internal or external circulation?

[SanRuth]

First turn on the external circulation of the air conditioning, then switch to internal circulation. Here are the relevant explanations: 1. External circulation: The principle of external circulation is to use a fan to draw outside air into the car while expelling interior air; it's mainly used when the cabin air becomes stale and needs refreshing. 2. Internal circulation: The air blown by the blower only circulates within the car without exchanging with outside air; during summer air conditioning use, internal circulation is activated to prevent hot outside air from entering the vehicle and compromising cooling efficiency.

[DelAdrian]

As a seasoned driver with over a decade of experience driving cars, whether to use the air recirculation or fresh air mode depends on specific scenarios. My experience is: In urban traffic jams, I use recirculation to avoid inhaling exhaust fumes and to cool down faster—I press it immediately when getting in the car during summer, cooling off comfortably in two to three minutes. However, don’t keep it on continuously, as stale air can cause dizziness. I usually switch to fresh air mode after about half an hour, especially during steady highway driving, where fresh air keeps me more alert. In winter, I use recirculation with the heater to save fuel, but it tends to fog up when idling at traffic lights, so I switch to fresh air or crack a window beforehand. My general advice is to switch modes frequently—it’s both car-friendly and healthier. I’ve tested this habit (except in rainy conditions) and found it reduces fuel consumption by 5%, which is quite cost-effective.

[SanAmelia]

I believe choosing between air recirculation or fresh air mode should prioritize air quality impacts on health. Living in a big city, I firmly use recirculation mode when air pollution is severe, as it blocks external dust and harmful gases to protect lungs – especially reducing allergy symptoms during smog days. However, prolonged lack of air circulation can lead to bacterial buildup inside the car. I activate fresh air mode several times weekly for ventilation, preventing dizziness or fatigued driving, and combine this with regular cabin air filter replacements for better effectiveness. On rainy days when humidity builds up inside, I use fresh air mode to prevent window fogging, ensuring clear visibility for safe driving. Personally, I start each morning with 5 minutes of fresh air mode to purify the cabin air, then switch to recirculation based on conditions to conserve resources. This balanced approach has significantly improved my breathing comfort, and I've recommended it to friends who found it helpful too.

[DelCaleb]

The air conditioning mode selection should be simple and practical. I recommend using the recirculation mode for energy saving and fuel efficiency, as it re-cools the existing cabin air without consuming energy to process fresh air. This is most suitable for slow urban driving and can help reduce fuel consumption. Only switch to fresh air mode when necessary, such as during long-distance driving to ventilate and reduce fatigue, or in smoky weather to improve the interior environment. Regular cleaning of the air conditioning system to prevent odor buildup is crucial. I check the filter every quarter to avoid bacterial growth that could affect health, ensuring efficient operation whenever switching modes.