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How to Change the Air Filter in Your HVAC System

Changing the air filter on your HVAC system is probably one of the best things you can do to keep your system running efficiently and help improve the air quality in your home.

How Your HVAC Filter Works

As the furnace or air conditioning system moves air throughout your house, the system’s air filter catches dust and other particles. When the filter becomes clogged, this can block airflow and make your system work harder than it needs to, using more energy. A dirty filter isn’t good for your home’s air quality either, as it lets contaminates and allergens build up in your home.

Where is Your Filter Located?

Your air filter is usually located in one of these two locations:

  • On the blower compartment of your furnace or air conditioner, in an attached filter case.

  • Behind a ceiling- or wall-mounted return air grille.

What Size Filter?

If you’re not sure what size and type of air filter your system requires, you’ll need to remove the current filter to check the dimensions.

Important: As you remove the filter, take note of the direction of the arrows on the filter’s edge. This will be important when you install the new filter.

After you remove the filter, see if the dimensions are written on the edge (length x width x height).

If the dimensions of the filter are not on the filter frame or edge, you’ll need to grab a tape measure. After you get the measurements, you’ll need to round the numbers up a little. For example, a filter that measures 19.5 x 13.5 x .75 means you need a 20 x 14 x 1 filter (in inches). Ideally, if you still have the HVAC system’s manual, you’ll find the filter dimensions listed there.

How to Replace the Filter

  1. Use your thermostat to turn off your air conditioner or heater.

  2. If you haven’t already removed the old air filter, remember to note the direction of the arrows on the filter’s edge as you take the old filter out.

  3. Insert the new filter with the arrows facing in the same direction as the old filter. The arrows should point in the direction the air is flowing. For a ceiling-mounted filter, the arrows should face up. For a filter next to your blower, the arrows should typically point towards the blower.

How Often to Change Your Filter

Most standard 1-inch air filters have a 3-month life, but when to change your filter depends on these factors:

  • How often do you run your HVAC system? If you live somewhere hot and humid and run your system all day every day, you may need to change your filter once per month.

  • Do you have pets, smoke, or have allergies? Your filter should probably be changed more often than every three months, which is the typical manufacturer recommendation.

HVAC Filter Tips

  • Write the date on the edge of the filter so you can see when it was last changed.

  • Sign up for a service that ships you filters at one, two, or three month intervals.

  • For heavy-use months, a good reminder is to change your air filter the day your new utility bill arrives.

1 Comment

Andrew Hayward
Andrew Hayward
May 03

I never realized how much of a difference a simple air filter change could make until our HVAC Contractor Delray Beach company recommended it. Now, with the new filter in place, our system seems to be running more efficiently and the air quality in our home feels noticeably better.

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