Which Way To Put An Air Filter In A Furnace

Which Way to Put an Air Filter in a Furnace?

Changing your furnace air filter is a simple task that can have a big impact on your home’s comfort and air quality. But one common question people ask is: Which way should you put the air filter in the furnace?

Here’s a quick guide to ensure you get it right!

1. Understand the Importance of the Air Filter

The furnace air filter plays a crucial role in keeping your home’s air clean by trapping dust, allergens, and other particles. A properly installed air filter also ensures your furnace operates efficiently, helping it to last longer and reducing energy bills.

2. Check the Airflow Direction

When replacing the air filter, the most important thing to check is the airflow direction. Furnaces are designed to pull air through the filter, so it’s crucial that the filter is installed correctly to allow for smooth airflow.

Each air filter will have an arrow printed on the side, indicating the airflow direction. This arrow should always point toward the furnace or the blower motor. Essentially, the air flows from the return duct into the furnace, and the arrow should follow that flow.

3. Locate the Filter Slot

In most furnaces, the air filter is located in the return air duct or the blower compartment. It may be in a horizontal or vertical slot near the furnace’s intake. Slide the old filter out, and if it’s covered in dust and dirt, it’s time for a replacement!

4. Insert the New Filter

Once you’ve identified the airflow direction, insert the new filter with the arrow pointing toward the furnace. Gently slide it into place, ensuring there are no gaps or bends.

5. How Often Should You Replace the Filter?

Regular maintenance is key to keeping your furnace running smoothly. At Green City Heating and Air, we recommend checking your air filter every month and replacing it every 1 to 3 months, depending on usage, household size, and whether you have pets or allergies.


Installing your furnace air filter in the correct direction is essential for maintaining good airflow, extending the life of your system, and ensuring clean air for your home. The arrow on the filter is your guide—just point it toward the furnace, and you’re good to go!

For more HVAC tips or professional help, contact Green City Heating and Air. We’re here to help keep your furnace running efficiently all year long!

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