Is it better to use the car air conditioner in recirculation mode or fresh air mode?

[LeNolan]

There is no absolute better or worse between the recirculation mode and fresh air mode of car air conditioning. It should be flexibly used according to actual situations. Relevant usage guidelines are as follows: 1. Road conditions: Use fresh air mode on highways. Firstly, due to wind resistance and speed, opening windows is not suitable on highways. If recirculation mode is used for a long time, it may cause brain hypoxia, affecting reaction and judgment, which is very dangerous. Secondly, the air quality on highways is generally good with low exhaust concentration, so fresh air mode can be chosen. In crowded urban areas or during rush hours when vehicle exhaust concentration is high, decisively switch to recirculation mode. 2. Vehicle condition: New cars usually contain high concentrations of toxic gases like formaldehyde. Therefore, for the first three to six months after purchasing a new car, it is recommended to use fresh air mode along with opening windows to enhance air circulation and dilute the concentration of toxic gases inside the car. 3. Air quality: In some regions where PM2.5 pollution is severe on certain days, with PM2.5 levels above 50 and air quality not being good, it is advisable to use recirculation mode to avoid excessive inhalation of PM2.5 particles by the lungs. 4. Season: When using air conditioning in summer, recirculation mode is recommended because fresh air mode allows hot outdoor air to enter the car, causing the air conditioner to work continuously in cooling mode with poor efficiency. In winter, if the heater is on, remember to switch to fresh air mode to prevent dizziness and chest tightness. Additional information: 1. Recirculation mode: This mode closes the airflow passage between the inside and outside of the car. Without the fan, there is no airflow circulation. When the fan is on, the airflow drawn in comes only from inside the car, creating internal airflow circulation. Recirculation mode effectively prevents external dust and harmful gases from entering the car, such as when driving through smoke, dust, odorous areas, or in heavy traffic, blocking harmful exhaust from vehicles ahead. Another function is to maintain temperature. 2. Fresh air mode: This mode uses the fan to draw outside air into the car, meaning the airflow channel between the outside and inside is open. The air blown by the fan comes from outside, and even without the fan, airflow is still drawn into the car while driving, replenishing fresh air inside. Sometimes, even when the fan is off, air still enters because the fresh air mode is set. In urban traffic jams, the car may fill with exhaust fumes due to the fresh air mode drawing in vehicle exhaust from the road.

[BrooklynLynn]

I've driven for many years and feel that both the air recirculation mode and fresh air mode have their uses. The recirculation mode is great for blocking dust and pollutants when outside air quality is poor, such as in traffic jams or on smoggy days, keeping the cabin air fresh and worry-free. However, prolonged use can make the cabin stuffy, with increased CO2 levels potentially causing drowsiness while driving, which is unsafe. The fresh air mode brings in outside air, quickly refreshing the cabin during highway driving or after rain, keeping the driver alert – though it may introduce polluted air when outdoor quality is bad. My recommendation is to use recirculation mode more often in urban areas to avoid exhaust fumes, and switch to fresh air mode for long-distance driving. Automatic climate control systems handle this switching automatically for greater convenience. During daily driving, remember to adjust flexibly based on weather conditions: fresh air mode on clear days, recirculation mode during rain. Regular switching helps prevent fatigue and ensures safer driving.