Should You Use External or Internal Air Circulation in Winter?

[ConnorFitz]

Correct practice is to alternate between external and internal air circulation in winter. Brief description of air circulation modes: Internal circulation means the air conditioning system closes external air intake and only recirculates air within the vehicle cabin. External circulation means the air conditioning system opens external air intake to draw fresh air from outside the vehicle. Usage of air circulation modes: If the vehicle is fully occupied, it's necessary to periodically switch to external circulation to maintain fresh air inside the cabin, which also improves passenger comfort. Prolonged use of internal circulation during long drives can lead to oxygen deprivation in the cabin, potentially causing driver dizziness, blurred vision, and reduced concentration. Alternating between both modes accelerates the cooling/heating effects of the air conditioning system while maintaining clean cabin air and a comfortable environment.

[StCassidy]

Whether to use recirculation or fresh air mode in winter depends on the situation. When I first get in the car and it's freezing, I definitely turn on recirculation first - this way the heater only warms the existing air inside the car, making it heat up super fast. Once the cabin is warm, I switch to fresh air mode to bring in some outside air. The main reason for this is to prevent the cabin from getting too stuffy, which can make people drowsy and cause windows to fog up. During traffic jams, you must use recirculation mode, otherwise you'll suck in all the exhaust fumes from the vehicle ahead. On highways, you can use fresh air mode more often since the high speed provides good air circulation. Also, don't keep recirculation on when there are many passengers - too much carbon dioxide can cause dizziness. If you notice window fogging, immediately switch to fresh air mode with the defogger button - this works much better than just using the wipers.

[Reed]

I'm particularly concerned about in-car air quality, as the recirculation mode in winter directly impacts health. While turning on recirculation heats up the car faster, prolonged use makes the air stale and uncomfortable to breathe, often causing drowsiness. So once the temperature rises, switch to fresh air mode to maintain air freshness. Windshield fogging requires special attention—using fresh air mode helps alleviate it since outside air is drier. Of course, during smoggy days or heavy traffic with exhaust fumes, temporarily switch back to recirculation. If someone smokes or eats in the car causing odors, immediately switching to fresh air mode helps dissipate smells quickly. It's advisable to develop a habit: after every 30 minutes of recirculation, switch to 5 minutes of fresh air mode for balance.

[DelAlivia]

The biggest advantage of using the recirculation mode in winter is fuel efficiency. The heating system doesn't have to constantly warm up cold air coming from outside, instead it circulates the already warm air inside the car, reducing the workload of the AC compressor. However, keeping recirculation on all the time isn't wise - prolonged use can cause window fogging that obstructs visibility and may lead to oxygen deprivation. Here's what I usually do: After a cold start, I run recirculation for about ten minutes to warm up quickly, then switch to fresh air mode. This balances fuel savings with safety. Cars with automatic climate control are more convenient as the system automatically switches between modes based on temperature and humidity. Just remember not to use recirculation mode for extended periods.

[AlexanderDella]

From a safe driving perspective regarding the recirculation mode, my experience is: In winter, using the interior recirculation heats up the car faster but carries more risks. The rapid increase in carbon dioxide concentration inside the car can lead to slower driver reactions. Last winter, I almost rear-ended another car because I felt drowsy while driving. Additionally, fogged-up windows can obstruct lane-changing visibility. Now, I start with the interior recirculation for about five minutes to warm up, then immediately switch to exterior recirculation for fresh air. On long drives, it's even more important to switch to exterior recirculation for three minutes every half hour to stay alert. If the windows fog up suddenly, don't panic—turn on both the exterior recirculation and the windshield defogger for immediate results.

[SanChristian]

From the perspective of air conditioning principles: Recirculation mode reheats the warm air inside the cabin, making it highly efficient for heating and fuel-saving; Fresh air mode draws in cold air and reheats it, resulting in slower heating but providing ventilation. The correct approach in winter is to first use recirculation mode for rapid heating, then switch to fresh air mode to introduce fresh air once the desired temperature is reached. Alternating between these two modes is the most scientific approach: it maintains a comfortable temperature while preventing window fogging or oxygen deprivation in the cabin. Use recirculation mode decisively in polluted urban areas, and switch to fresh air mode on elevated highways or freeways. Vehicles with automatic climate control can be set to intelligently switch modes based on temperature, while drivers with manual air conditioning should remember to operate the buttons flexibly.