When using the air conditioner, you should leave the door slightly ajar

Air conditioners cool rooms by recirculating indoor air in a closed-loop system. Most models do not bring in fresh air from outside, except for a few specialized units equipped with fresh air intake features, according home appliance expert Nguyen Minh Tien.

The system draws warm air from the room, cools it through chilled copper coils, and then circulates it back. While this lowers the temperature, it does not refresh the air or improve ventilation.

To ensure cooling efficiency, manufacturers advise keeping doors and windows closed to prevent cold air from escaping. If too much outside air enters, the AC may struggle to reach the set temperature, consume more electricity, and fail to cool the room effectively.

However, Tien warns that sealing a room too tightly for extended periods can reduce oxygen levels and increase carbon dioxide, making the air stuffy and potentially affecting health.

To maintain both comfort and ventilation, he recommends leaving the door slightly open or ventilating the room periodically. Another option is installing a small exhaust fan opposite the air conditioner to help circulate air. These fans can run continuously at low speed or be set on a timer to operate every 30 to 60 minutes.

In some homes, especially those with wooden doors or ventilation grilles above doorways, a certain level of airflow may already exist. Still, Tien advises adopting simple ventilation practices to ensure a more comfortable environment, especially after sleeping in an air-conditioned room.

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