Should You Use Cold or Hot Air to Defog the Windshield?
2 Answers
You can use either cold or hot air to defog the car windshield. 1. Generally, cold air is used to remove fog. When cold air is blown onto the glass, the fog dissipates quickly, providing a fast and direct effect. This happens because the cold air creates a "cold barrier" on the glass surface, preventing carbon dioxide from condensing on the glass, thus defogging it. 2. Hot air can also disperse the fog, but since the water temperature is low when the car is first started, it takes some time for the air conditioning to blow hot air. Therefore, using hot air takes longer than using cold air. Additionally, when hot air is first blown, the fog inside the car may temporarily increase due to the greater temperature difference between the inside and outside. However, once the hot air dries the moisture inside the car, the fog will disappear.
I haven't been driving for long, and I get frustrated every time the windows fog up in the rain. I used to try hot air, but it took forever to clear; later, I found that cold air works fastest to defog, especially in summer or humid weather. The method is simple: turn on the AC, press the AC button to light it up, turn the temperature knob to the lowest setting, and adjust the airflow to blow at the windshield. The fog disappears in seconds—much more satisfying. However, if the air is too cold, you can put on a jacket. Preventive measures are also important: keep the windows clean or spray anti-fog products. For long drives, after the fog clears, you can switch back to warm air for comfort. In short, cold air is reliable for emergencies, and it's good to make it a habit to turn it on as soon as fog appears.
