How to Change Your Furnace Filter

When it comes to changing out your furnace filter, there are two key rules you should follow:

  • Make sure you have the right size replacement filter
  • Don't wait too long between changes

Here at Filterbuy, we recommend replacing your air filters out at least every 90 days or 3 months, especially for heating and cooling equipment. However, in some cases, it might make more sense to change them sooner rather than later, which is why checking the furnace filter should be a monthly maintenance measure.

Dust, dirt, pollen, carpet fibers, pet dander - these are all the things that your furnace filter takes out of the air to help keep your house cleaner, improve your indoor air quality, keep your seasonal allergies under control and keep your HVAC system running efficiently.

Many homeowners have no idea what a vital role their furnace filter plays in the heating and cooling system. When your existing filter is clean and working well, your furnace is efficient. Without a bunch of dust and debris coating and clogging up the components, air flows freely, and the blower motor lasts longer. The furnace filter also prevents clogs from forming in your central air's compressor coils.

All of this adds up to one thing, changing your furnace filter is extremely important.

Before we get started on how to go about doing that, we'd like to take a moment to remind readers that buying furnace filters in bulk is highly recommended since they'll be replaced regularly. In addition, when you buy in bulk, you'll have extras on hand when you need them and can save money in the process.

Does Your Central Air Unit Have a Furnace?

The first step in replacing a furnace filter is determining whether you need a furnace filter. Not all central air systems have a furnace filter. It could be a matter of not having a furnace in general or the filter being located in another more centralized spot.

How to Quickly Tell If You Have a Furnace Filter

  • Locate the air blower or furnace box, which should be near the main air handler. Most furnace filters are located in or around the blower.
  • Look to see if there's a slot for a furnace filter. The filter compartment could be in one of three spots:
    • On the side, in an intake rack.
    • In a door on the bottom.
    • In a door on the top.

If you see a compartment, you'll need a furnace filter. If you don't see a slot or door, you likely have a central air unit with two intake filters rather than a furnace box filter. There might also be no heating component; therefore, a furnace filter isn't needed.

How to Properly Change a Furnace Filter

Once you've determined if you need a furnace filter, you've got to regularly check how dirty it is and learn how to replace it. But there's no need to worry even if you don't have a single DIY bone in your body. Replacing your furnace filter is one of the easiest home maintenance tasks you'll ever tackle.

Step 1: Turn Off the Furnace

For modern heating systems, this may not be necessary because they utilize an electric pilot component. Older furnaces often had a gas pilot light that would continuously burn when the gas was on. For all furnace systems, it's best to shut them off completely if you're replacing the furnace filter.

Step 2: Open and Label New Furnace Filters

If you follow the advice of experts and buy in bulk, label each new filter with the date you plan to install it. Space them out by 3 months during the heating off-season and every 30 days during times when you'll be regularly running your heating system.

Step 3: Locate Your Furnace Box and the Door Panel for the Filter

Open or slide the door panel to get access to the furnace and filter. As mentioned above, you usually find the furnace filter near where the cool air enters the furnace in the cold air return duct or the entrance to the blower chamber (or sometimes in both locations).

Step 4: Remove the Old Furnace Filter

Remove the old and dirty air filter and set it aside to be properly recycled.

changing his dirty furnace filter and wearing blue gloves

Step 5: Install the New Furnace Filter

Slide your replacement and clean furnace filter into the slot, ensuring the filter media side goes against the airflow. Make sure the airflow arrows on the side of the new filter are pointing in the right direction toward the blower and away from the cold air. Replace the panel or door, and you're done.

installing new furnace filter

Step 6: Turn the Furnace Back On

Again, for newer furnaces, this may not be a necessary step, but for older furnaces, you'll need to turn the gas back on and reignite the pilot light so the filter can start doing its job.

Furnace Filter Changing FAQs

Is a furnace filter the same as an air filter?

Not quite. While they are very similar in how they function, a furnace filter is specifically designed to work in the furnace. But that's essentially the only difference between a furnace filter and an air filter.

What if I have a plastic-framed air filter?

A plastic-framed air filter can indicate a customized fit is needed. As a manufacturer, Filterbuy offers custom-sized furnace filters when a standard size won't fit. But no matter what, you need to verify all plastic frames are flame resistant.

How often should I change my furnace filter?

At least once every three months. If the furnace is run frequently, the filter should be changed every 30 days.