Air Conditioners Fog Or Smoke Coming Out Air Vents

Fog or smoke coming out the air vents is caused by cold dry air coming in contact with warmer, more moist air near the air conditioner. If the air temperature near the unit is below the dew point, this causes water vapor to form in the air and condense into water droplets, thus causing the fog or smoke.

A dirty filter or low fan speed may aggravate the condition. These conditions reduce airflow causing more or slower exposure of the cold air to the moist air. The higher the humidity in the room the worse the fog or smoke may be.

To Minimize Fog:

  1. Check and clean the air filter if dirty. For more information, see Air Conditioners Cleaning the Filter
  2. Run the fan on High speed, which will cool the room air faster and circulate it into the room better.


The fog or smoke should disappear rapidly, usually in less than a minute or two, as the air conditioner removes the humidity from the air and the room air becomes cooler.