Furnace Filter Maintenance

Furnace filters need to be changed on a regular basis to keep clean air circulating throughout your home. How often you change it and what type of filter you need depends on a number of factors. Watch this video and learn more about how to improve the air quality in your home as well as the efficiency of your furnace.



  1. Furnace Filter Maintenance - Step 1

    Turn your furnace or air-conditioner unit to the “off” position.

  2. Furnace Filter Maintenance - Step 2

    Look for an indication on the side of the filter for the direction of air circulation.

  3. Furnace Filter Maintenance - Step 3

    You can see which way the filter needs to be facing by looking at the old filter when you pull out it.

  4. Furnace Filter Maintenance - Step 4

    Insert the new air filter.

  5. Furnace Filter Maintenance - Step 5

    Close the furnace or air conditioning unit.

  6. Furnace Filter Maintenance - Step 6

    Turn the furnace or air conditioning unit back on.

Read Video Transcript

If your home has a forced air heating system, one of the best things you can do to improve indoor air quality is to change your furnace filter on a regular basis. Replacing your filter can also help improve the efficiency of your furnace, which will reduce energy costs. It’s also one of the easiest home maintenance projects that you can do. All it takes is a basic understanding of your home’s heating system, and a filter that fits both your furnace and your needs.

Today, we’ll show you how to access the filter compartment in your furnace so you can replace your filter. We’ll also show you several different types of filters and what each is designed to do. Then we’ll give you some tips on how frequently you should change the filter in your furnace.

So let’s get started.

The way a typical forced-air heating system works is really quite simple. A fan within the furnace blows heated air through the duct system, which carries warm air to various rooms throughout the house. Then, a system of return ducts bring the unconditioned air back to the furnace where it is heated before continuing the air circulation loop.

Right before the air is returned to the heater, it flows through the air filter to remove any airborne debris, including things like dust, pollen, mold spores and other microscopic particles. This ensures that the air returning to the furnace is as clean as possible.

Problems arise, however, when the filter has been neglected for too long. A clogged filter reduces air flow to the furnace, which requires your furnace to work harder than normal, wasting energy.

The solution is simply to change your furnace filter on a regular basis. But how often you need to change your filter depends on several factors.

The first factor is your home’s environment. Airborne particles like dust, pollen and pet dander are one of the leading causes of indoor air pollution.

So how often you need to change your filter depends on things like if there are pets in the house, or if there is a construction project going on that might create more dust than usual. Dirty ductwork can also play a role.

The other factor in how often you will need to change your filter depends on what type of filter you have.

To get a better understanding of how a filter works, let’s take a look at several different types of filters. These are all 1-inch thick filters. The difference between the three filters you see here is the type of media used and the construction of the filter. Each filter has a performance rating, based on its ability to capture particles in the air.

This first filter has a fiberglass media. This is considered an economy filter. Hold it up and you can almost see through the fiberglass media, which indicates that this filter isn’t a top performer when it comes to cleaning your home’s air.

These two filters are called pleated filters, because as you can see, the filter’s fabric has pleats, which provide more surface area to capture airborne particles. In addition, both of these filters are electrostatically charged, which means they use static electricity to attract microscopic particles.

This first filter is rated for larger particles such as mold spores, pollen and dust mite debris. It has a performance rating nearly 10 times that of the fiberglass filter. This second filter is rated for even smaller particles, such as smoke, pet dander and household dust. In comparison, it has a performance rating two and a half times greater than the middle grade. It also has more pleats and a wire backing on both sides of the filter medium for durability.

Filter construction is important because you don’t want it to break down and get sucked into the fan, which might damage the system. Now, all we have left to do is to install our new filter in the filter compartment.

Before you do this, first turn your thermostat to the off position to make sure your furnace or air conditioner unit isn’t running during the installation of the new filter.

Next, locate the filter compartment. It is usually located where the return supply duct enters the furnace. You may have to consult your owner’s manual that came with your furnace for the exact location.

The main thing to remember here it to make sure you have the air filter inserted in the right direction. Each filter has an arrow that denotes the direction of air flow into the furnace. The easiest way to tell is to note the air-flow arrow in your old filter when you take it out. Insert the new filter in the same direction, close the compartment and turn the unit back on at the thermostat.

Now comes the toughest part: remembering to change the filter according to the manufacturer’s recommendations, which in our case is in three months. Some filters come with a sticker to help remind you.

Well that’s it. Now you can breathe easier knowing that you’ve done something good for your furnace and for your health.

If you have questions about this or any other home improvement project, be sure to read our list of Frequently Asked Questions for this video. And be sure to print out our Project Instructions, which includes a Tools and Materials checklist, before visiting your local independent home improvement retailer. That’s where you’ll find all the products and helpful advice to complete your project. If you’re not sure where to find your local store, check out our Store Locator.

Good luck with your project and thanks for watching.

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9 responses to “Furnace Filter Maintenance”

  1. Arlyn Murphy says:

    My filter is at the bottom of my system. Wouldn’t you know it. I forgot what direction it was in. Should the arrow be pointing to the bottom or to the top? Thanks!

    • Bob says:

      The “air-flow direction arrow” printed on the new filter should be pointed towards your furnace (or more specifically; arrow pointed towards your furnace fan unit).

  2. Tangie says:

    My air filter is the one with the bigger pleats and the grate on the back. I don’t think it is doing a good enough job because we have a thick layer of dust on our tv screen when the room humidifier and the heater are on at the same time. How can we get our ducts cleaned and would getting an are humidifier built into the furnace be better that a room humidifier?

  3. Hillel Strouse says:

    My heater has a woven fiberglass filter with no surrounding cardboard . I was told it can be cleaned by hosing it with water which I do every year before winter. Is that correct or What should I really be doing ?

  4. Hillel Strouse says:

    Additional to question … The fiberglass is very thick

  5. Joe says:

    Hi Bob. If a 30 something year old part is changed in a furnace, would it have any soot or dust on it. A part was replaced and I asked for the old part to show my son, and it looked brand new.

  6. Ada says:

    Oh, when it comes to complexities like this, I find it easier to call a local service like https://excelsiortwincities.com/heating/repair-and-maintenance/ which will do the job for me. I am simply afraid of such systems, and it is unlikely that there will be enough skills to repair or maintain them myself.

  7. Nina Paul says:

    Thanks for sharing this. I didn’t know indoor plants can be that much useful.

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