Should the Air Recirculation Be Turned On When Using Car Air Conditioning?
3 Answers
Whether to turn on the air recirculation when using car air conditioning depends on the specific conditions inside the vehicle and the driver's intention. The function of the external air circulation is to replenish fresh air. It uses a fan to draw outside air into the car, meaning the air passage between the inside and outside of the vehicle is open. The function of the internal air recirculation is to block polluted air. Below are relevant details: Function of external air circulation: When external air circulation is activated, the air intake located at the firewall is opened by the air conditioning system's computer. The car's blower then draws outside air through a micro-dust filter into the two heat exchangers (cooling and heating) inside the evaporator. The air, after passing through the heat exchangers, is blown out through the vents. When the vehicle's air conditioning system is in external air circulation mode, the air intake is open, connecting the inside and outside air. For example, if you encounter heavy traffic in the city and turn on the external air circulation, the car will be filled with exhaust fumes because the inside and outside air are connected via the external circulation. Function of internal air recirculation: In internal air circulation mode, the airflow passage between the inside and outside of the vehicle is closed. Without the blower, there is no airflow circulation. When the blower is on, the air drawn in comes only from inside the car, creating an internal airflow cycle. The internal air recirculation primarily and effectively prevents external dust and harmful gases from entering the vehicle, such as when driving through smoke, dust, areas with strong odors, or in heavy traffic, blocking harmful exhaust emissions from vehicles ahead.
When driving, whether to use the air recirculation mode depends on the situation. On extremely hot summer days, turning on the recirculation mode right after starting the car can cool down the interior quickly by keeping the cold air circulating inside without escaping, which reduces the need for the AC to run at full power and saves some fuel. However, prolonged use can degrade the air quality inside the car, and high carbon dioxide levels can make you feel drowsy. In such cases, switching to fresh air mode to bring in some outside air is more comfortable. If it's a smoggy day or you're stuck in traffic with heavy exhaust fumes around, you must use the recirculation mode to avoid inhaling pollutants. During highway cruising, I prefer the fresh air mode, as the natural airflow helps prevent window fogging. Simply put, switching flexibly is the most practical approach, ensuring both comfort and health.
From the perspective of fuel efficiency and cooling effectiveness, using the air recirculation mode when the AC is on is indeed necessary. The cold air only circulates inside the cabin, eliminating the need to repeatedly cool down the hot air drawn from outside, which reduces the compressor's workload and naturally lowers fuel consumption. Additionally, the cooling speed is significantly faster, especially after the car has been exposed to high temperatures and sunlight—just five minutes in recirculation mode can noticeably cool down the cabin. However, prolonged use of recirculation can lead to a drop in oxygen levels inside the car, so I usually switch to fresh air mode for a few minutes every half hour or so. If the car is equipped with a PM2.5 filtration system, it's even better to use fresh air mode more often in combination with the filtration function. Remember, the most fuel-efficient practice is to use recirculation until the desired temperature is reached and then increase the fan speed rather than lowering the temperature further.