Is it necessary to ventilate the room when air conditioner is on?

When using an air conditioner, it's generally not necessary to ventilate the room, as AC units are designed to cool and dehumidify indoor air efficiently without bringing in outside air. However, occasional ventilation can be beneficial to improve indoor air quality, especially if there are pollutants or stale air. If the air conditioner is running in recirculation mode, it continually filters and cools the existing air. In contrast, introducing fresh air can increase energy costs and may reduce cooling efficiency.