Car air conditioning: Should it use recirculated or outside air?

Most car models currently on the market are equipped with both recirculating and outside air intake modes by the manufacturer. However, not all drivers know when it is appropriate to use recirculating or outside air intake.

Both of these air intake modes are part of the car's air conditioning system and can be adjusted via function buttons located on the dashboard. Essentially, these two modes are used to draw air from either outside or inside the vehicle before it passes through the evaporator and heater coils of the air conditioning system to maintain the temperature in the car's interior.

Specifically, when the user selects the outside air intake mode, the vehicle's air intake system draws air from outside the vehicle into the air filter. This air then passes through the air conditioning system's evaporator or heater to adjust the temperature to the user's chosen level. This air intake mode creates a fresh airflow while maintaining sufficient oxygen levels in the vehicle's interior.

However, when driving through dusty or smelly areas, if the user still selects the outside air intake mode, dust, humid air, or unpleasant odors will enter the car.

To reduce fuel consumption and sudden temperature changes when entering and exiting the vehicle, it's generally recommended to select the outside air intake mode and slightly open the windows when the car is first started and the air conditioning is not yet on. After turning on the air conditioner (A/C), close the windows and switch to the inside air intake mode for faster cooling.

In recirculation mode, the air conditioning system directly draws in the circulating air from the car's interior and passes it through the evaporator and heater to change the temperature. Given the weather conditions in Vietnam, on hot days, recirculation mode provides faster cooling compared to using outside air, because the temperature inside the car is always different from the outside temperature.

However, in vehicles not equipped with automatic air conditioning, selecting the recirculating air mode and using the car for extended periods can easily lead to a lack of oxygen inside the vehicle, causing stuffiness and fatigue for passengers.

Therefore, if the car is only traveling short distances or in city areas, it's advisable to use the recirculating air mode to limit the amount of dust and pollutants entering the vehicle. However, when driving long distances, especially with cars using manual air conditioning systems, it's recommended to occasionally choose areas with fresh air and switch to the outside air intake mode to ensure sufficient oxygen levels inside the car.

In vehicles with automatic air conditioning systems, if the user selects the recirculating air mode and the sensor detects insufficient oxygen levels inside the vehicle, it will automatically switch to drawing in outside air. Therefore, in some cases, users should also be aware of this to avoid dust, smoke, and odors from outside entering the vehicle and causing discomfort to passengers.

When driving in rainy conditions, prioritize the recirculating air mode to prevent moisture from entering the vehicle, which can cause mold and damage the air conditioning system. In addition, users should pay attention to cleaning and maintaining the air conditioning system, replacing the air filter regularly, and cleaning the interior.

As you can see, choosing between recirculating and outside air intake modes in a car depends on whether the car is equipped with manual or automatic air conditioning, as well as the weather conditions and outside air quality. Users should flexibly choose between the two air intake modes to ensure a fresh and airy atmosphere inside the car.