Which Air Circulation Mode to Use for Defogging Inside the Car?

[OStephanie]

Using the air recirculation mode can help defog the windshield faster. Here is a brief introduction to the recirculation and fresh air modes: Recirculation Mode: The purpose of the recirculation mode is to prevent dust and odors from entering the car through the fresh air intake. Therefore, a control system is set up to close the fresh air duct, blocking polluted air from outside the vehicle. Fresh Air Mode: Since the interior of the car forms a relatively sealed environment, prolonged exposure can lead to oxygen deprivation. To address this, the air conditioning system includes an additional duct that draws in fresh air from outside. This air is then passed through the air conditioning evaporator or heater core to deliver either cool or warm air.

[McSebastian]

As a veteran driver with twenty years of experience, I know exactly how to deal with fogging. The key is to use the external air circulation combined with the air conditioner's dehumidification function! Fogging occurs when the glass temperature is below the dew point, and internal circulation keeps recirculating the moist air inside. Simply press the external air circulation button (marked with a car and an arrow), and the AC system will draw in relatively drier outside air. Then, turn on the AC switch—the compressor will remove moisture, significantly speeding up defogging. If it's cold in winter, add some warm air to raise the glass temperature. Remember, never rely solely on internal circulation, or the fog will only get worse! I keep my car in external air circulation mode year-round and rarely experience fogging.

[LeVivian]

From a physical perspective, defogging requires balancing air humidity and temperature. Using the external air circulation is the fundamental solution: the absolute humidity of outside air is usually lower than that inside the car, especially when passengers' breathing creates moisture on rainy days. After dehumidification by the air conditioning evaporator, dry air is blown onto the glass surface, preventing water vapor from condensing into fog. Internal circulation is only suitable for sandstorms or severe pollution, as it tends to accumulate moisture under normal conditions. Additionally, ensure the air vents are directed at the windshield during defogging, and avoid setting the temperature too high. This small detail can improve defogging efficiency by 50%.

[DeStella]

Don't panic when fogging occurs, remember the three-step mantra: First, turn the fan button to maximum speed; second, press the car icon to switch to external circulation; third, turn on the AC light to activate dehumidification. The key is definitely external circulation! It's best to perform these operations while parked to ensure safety. At the same time, slightly open the driver and passenger windows to accelerate air circulation, and close them after the fog dissipates. On rainy days, it's recommended to turn on the defogging function in advance to maintain dryness. Be alert when the wipers can't clear water marks cleanly, as fog may form again. These tips can be used for daily commuting.