How Often Should You Change Your Furnace Filter?

January 5, 2021

Furnace filters need to be changed whenever they get dirty. Unfortunately, there is no single answer for how long this takes as everyone’s situation is different. The rule of thumb is every three months, but you might need to change it more or less frequently.

Signs You Need a New Furnace Filter

You can pull the filter out and look at it. If it’s visibly dirty, then change it. If your HVAC system is running more often than normal, that’s a sign you need a new filter. Other signs are more dust in your home than normal and odd smells coming from your furnace.

Carlos Warren & Son in Dexter, MO, will inspect and change filters if needed during an annual maintenance appointment. We take pride in offering customers high-quality furnace tune-ups.


If you have pets, you need to change the furnace filter more often. If you have one pet, change the filter every two months. With more pets, you might need to change it every month.

Allergies and Asthma

If anyone in your family is allergic or has asthma, you need to frequently change the furnace filter. A good quality filter is effective at trapping things like dust mites, dander, and pollen.

Frequently Open Doors and Windows

If you often keep doors and windows open in the summer, you’ll let in a lot of dust and contaminants from the outdoors. These collect on the filter, so check it often and replace it every one to two months as needed.


If one of your family members smokes in the house, it will affect your furnace filter. With one smoker, you should probably change it every other month.

Carlos Warren & Son is a business that does heater and air conditioner repairs, installations, and maintenance. We also provide indoor air quality solutions, such as Lennox PureAir air purification systems. Get in touch with us today to find out more.

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