How to Determine Air Flow Direction in an Air Conditioner

An air conditioner takes in room air, cools it and blows it back out into the room, creating an ongoing exchange of air.
Determining the airflow of this cycle is important because it helps in positioning air filters, which are crucial for keeping dirt and dust out of the unit. Understanding where the air exits the unit for cooling makes it possible to determine if air flow is sufficient or if there is a problem with the mechanical or other parts of the unit. It’s a simple process to determine the air flow in your air conditioner. .

Step 1

Locate the return-air vent. It is usually in the same general area as your thermostat. This is also where the air-conditioner filter is located. Room air enters the air-conditioning unit at this return-air vent.

Step 2

Notice where the ducts go after the air is cooled. They branch out to the various rooms of the home.

Step 3

Find the registers, or small grates that aim cool air into the rooms. These are at the the ends of the ducts and are usually located in the ceiling or floor. They are smaller than the return-air vent grate. Air leaves the air conditioner at these points to cool the rooms. Air is then sucked into the return duct once again, filtering out dust and dirt.


  • Many air-conditioner filters filter only one way. Install them correctly, following the arrow printed on the filter. The arrow should point in the direction of air flow, that is, the arrow should be pointing toward the unit rather than toward the room.

About the Author

In 2007 Nannie Kate discovered that the words she had been writing all her life had an actual cash value. She's been writing professionally through brokers ever since. With an English major background she creates articles and ebooks on a wide variety of subjects.