Should You Use Internal or External Air Circulation When Turning on the Heater in Your Car?

2 Answers
MacOscar
07/28/25 4:21pm
Whether to use internal or external air circulation when turning on the heater in your car depends on different situations: 1. Use internal circulation when the outside air quality is poor, when you need to quickly heat the car interior, or when you want to maintain warmth inside the car. Internal circulation prevents outside air from entering the car, only recirculating the air already inside. This helps block harmful substances from entering with fresh air and also helps retain warmth. 2. Use external circulation when the outside air is clean, or when the car has been using internal circulation for a long time and needs fresh air. External circulation uses a fan to draw outside air into the car, meaning the air ducts between the outside and inside of the car are open. The air blown by the fan comes from outside, and even if the fan is off, airflow is still drawn into the car while driving, replenishing fresh air inside. For example, during long highway drives, not ventilating for extended periods can make the air inside the car stale, so it's necessary to turn on external circulation to refresh the air promptly.
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MacAdelyn
08/11/25 11:17pm
As a long-time car owner, I've found that the key to using the heater in winter is flexibly switching between recirculation and fresh air modes. When getting into the car with fogged-up windows, I usually first set it to fresh air mode to let dry outside air flow in, quickly clearing the fog for better visibility. After about a minute when the fog dissipates, I switch to recirculation mode. This efficiently heats the interior air without wasting warmth on cold outside air, making temperature rise faster and more energy-efficient. If you accidentally keep using recirculation mode, the cabin air can become stuffy or oxygen-deprived, potentially causing driver fatigue. Therefore, I recommend switching back to fresh air mode for a few minutes every 30 minutes during highway or long-distance driving for ventilation. I've maintained this habit for years, ensuring both comfort and safety. Especially on rainy or snowy days when outside air has lower humidity, using it for defogging is particularly effective.
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