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How Often Should You Change a Furnace Filter? Reasons, Facts & FAQs

furnace at the basement

If you have an HVAC system regulating the temperature in your home, you likely have a furnace filter that you need to change occasionally. Many people want to know how often they need to replace these filters, and the short answer is every 3 months. However, there are many factors to consider, so keep reading as we look at what these filters do and how to know when you need to replace them.

divider 7 What Does the Furnace Filter Do?

The furnace filter is responsible for cleaning the air going into the furnace. The air in your home contains the oxygen needed for fire to burn and create heat. However, it also has many contaminants that can gunk up the system, significantly reducing its lifespan and increasing the amount of maintenance that you need to perform on your furnace every year. The filter helps remove these contaminants. Since the furnace pulls air through the filter, it also effectively works as an air purifier, helping to remove contaminants from the air that you breathe.

Image By: Peter Gudella, Shutterstock

How Do I Know When It’s Time to Change the Furnace Filter?

In most cases, you can visually inspect the filter to see if it’s time for a change. Filters that need replacing will have a thick coating of contaminants on them that are easily visible, and you can even usually remove some of it with your fingers. In extreme cases, dust will get into the air, and the filters may also be discolored. A new filter will not have these issues and will be visibly clean.

How Often Should I Change My Furnace Filter?


The standard suggestion is to replace the filter every 3 months. Changing it this often will help ensure that there’s not too much strain on your HVAC system caused by a clogged filter. However, if you live in a rural part of the country and have clean country air and no pets or family members who smoke cigarettes, you will likely need to change your filter far less frequently than someone who lives in a smog-polluted city with cats, dogs, and smokers. Since the number of contaminants can vary from one home to the next, it’s important to inspect the filter frequently and change it if it looks bad.

Filter thickness

Filters have various thicknesses, from 1 to 5 inches. A thick filter can hold more contaminants than a thin one, so you will need to change it less frequently.

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What if I Don’t Change My Filter in Time?

If you allow your filter to become too clogged with contaminants, it will prevent the air from flowing through freely, putting additional strain on the furnace as it tries to get enough oxygen. The result of a clogged filter can vary from increased energy costs due to the furnace running longer because it’s not burning efficiently to a damaged system that requires professional maintenance.

HVAC Tech Working On A Gas Furnace
Image Credit: Indy Edge, Shutterstock

How Can I Make My Filter Last Longer?

Unfortunately, there’s not much that you can do to extend the life of your filters, as you have limited control over the air around you. However, if you have pets, you can brush them frequently to help reduce the amount of loose fur in your home, and if you are a smoker, you can try to smoke outside, as cigarette smoke will clog the filter quickly.

How Do I Change My Filter?

Most systems have a door that you can open to access the filter to change it. Some may require you to remove a screw, but replacement is quick and easy. Open the door, remove the old filter, insert the new filter, and close the door.

divider 7 Summary

You should change your filter once every 3 months to keep your HVAC system working at peak efficiency. In clean air environments, it might last longer, but you should change it more frequently in areas with smog, cigarette smoke, or pet dander, as these items can quickly clog the filter, putting additional strain on your system.

Featured Image Credit: oasisamuel, Shutterstock


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