Many people say that if you don’t keep the doors tightly closed while the air conditioner is running, wouldn’t that waste electricity? At first, I thought the same. But after listening to the experts, I realized I had been doing it wrong.

Why shouldn’t you keep the doors tightly closed when using the air conditioner?

Most people shut their doors so tightly that no gaps remain when turning on the air conditioner, thinking this will prevent cool air from escaping, keep the room cooler, and save electricity. In reality, however, once the air conditioner starts running, the air it blows out can mix with dust and bacteria, since the air outlet will accumulate a certain amount of dust over time.

If the door is kept completely shut, the dust and bacteria will remain trapped inside the room instead of escaping. According to Tipsmake, the air inside a tightly closed, air-conditioned room can be 2–5 times more harmful than outdoor air.

Breathing in this polluted air over a long period can cause significant harm to human health, especially for the elderly and children, who are more prone to respiratory illnesses.

In addition, closing the room tightly causes the air to be trapped inside, increasing the room’s pressure. This pressure then pushes the cool air into cracks or small gaps around windows, walls, ceilings, or floors, which actually leads to energy waste.

Moreover, when the room reaches the set temperature, the cooling system of the air conditioner will temporarily stop, making the room lack fresh air. That’s why many people who stay in an airtight, air-conditioned room for a long time feel breathless, suffocated, uncomfortable, and tired.

So how should you open or close the door when the air conditioner is on?

Keeping the door completely closed while running the air conditioner is not advisable, but leaving it wide open is also wrong. The correct way is not to close the door tightly right away. Instead, after the air conditioner has been running for about 10–15 minutes, you should then close the door. This allows dust and bacteria inside the unit to be expelled along with the airflow, preventing them from circulating in a sealed space and being inhaled.

In addition, every 15–30 minutes, you should briefly open the door for a few seconds to let the room “breathe” and exchange air with the outside. Alternatively, you can leave small gaps in the room or install a ventilation fan to keep air circulating freely, which prevents pressure buildup, helps the air conditioner cool more evenly, and reduces energy consumption.

Additional expert advice

Even though hot weather makes people want to stay in air-conditioned rooms all the time, experts recommend not staying inside continuously for more than four hours. Otherwise, your body may lose its ability to adapt to normal temperatures. Ideally, every 2–3 hours, you should step outside into the regular environment for a while.