Is it safe to run the air conditioner all day during summer heat?

"With an elderly family member and a 2-month-old daughter at home, I usually keep the air conditioner running all day to keep the house cool, but I worry it might cause my baby to develop pneumonia or a sore throat. What should I be careful about?" Ha, 27, from Hanoi, asked.

A air conditioner. Photo by VnExpress/Tuan Hung

Thang said air conditioning is essential during extreme heat, but improper use can pose health risks. Sudden shifts between outdoor heat and cool indoor environments can trigger thermal shock, causing dizziness, narrowed blood vessels, or even stroke.

Poorly ventilated air-conditioned rooms can also trap dust and promote the growth of bacteria, viruses, and mold, raising the risk of respiratory issues such as coughing, sore throat, bronchitis, and pneumonia.

To use air conditioning safely, Thang recommended keeping the room temperature between 26–28 degrees Celsius and increasing it to at least 27–28 degrees once the space is cool. He advised against leaving the unit on all day. Instead, set a timer to turn it off between 3–4 a.m., then switch to a fan on low speed.

Avoid directing airflow toward the face or head, which can lead to nasal congestion and breathing difficulties. Those who sweat heavily after working outdoors should wipe off before entering a cooled room to prevent chills or dehydration, he added. People with lung conditions, weakened immune systems, or chronic respiratory issues should use air conditioning with caution. The unit should be cleaned two to three times a year to prevent microbial buildup.

To counteract dry indoor air, he recommended drinking plenty of water and using moisturizer on exposed skin areas such as the face, neck, hands, and feet. When not using the air conditioner, open windows to let in fresh air. Cooling fans, misting fans, or ceiling fans can also help maintain comfort while reducing health risks.