What is the use of the external air circulation mode in a car?
2 Answers
The external air circulation mode is primarily used when the air inside the vehicle becomes stale and requires ventilation. The working principle of car external circulation involves using a fan to draw outside air into the cabin while expelling interior air outward through the fan. Additionally, the external circulation mode can help defog the windshield during rainy weather. Extended information: The internal and external air circulation modes refer to the air intake direction of the AC system, drawing air from either inside or outside the vehicle. Under normal circumstances, we generally use external circulation to bring fresh outside air into the cabin. However, when encountering poor external air quality or needing to quickly achieve ideal cabin temperature, internal circulation should be used. This means when there's a significant temperature difference between inside and outside the vehicle, short-term use of internal circulation with AC can rapidly adjust cabin temperature. The following situations typically require internal circulation: 1. When external air quality is poor with severe pollution, such as dusty roads, congested traffic areas, or routes near chemical plants with foul odors. 2. During summer, to quickly cool down the cabin using AC. 3. In winter, using internal circulation can help maintain warmth inside the vehicle. The following situations require external circulation: 1. After prolonged use of internal circulation when opening windows isn't convenient, periodically switching to external circulation brings fresh air into the cabin. 2. When there are multiple passengers in the vehicle, using external circulation maintains air freshness while preventing excessive humidity that could cause window fogging. Note: Avoid prolonged use of internal circulation as it may lead to stale and unhealthy air quality inside the cabin.
Having driven for decades, I find the car's fresh air mode particularly useful, mainly for allowing fresh air to flow into the vehicle and preventing the interior air from becoming stuffy and dirty. When driving in the city for extended periods with windows closed, the accumulation of carbon dioxide from everyone's breathing can easily cause dizziness or drowsiness. At such times, activating the fresh air mode allows the air conditioning system to draw in outside air, diluting the stale air and making driving much more refreshing. I remember once on a long trip during hot weather, using only recirculation mode caused high humidity inside the car, leading to fogging. Switching to fresh air mode with the fan helped balance the humidity and even saved some fuel. I recommend using fresh air mode more often on highways or in areas with good air quality. However, during smoggy conditions or in areas with heavy exhaust fumes, remember to switch to recirculation mode to protect your health.
