How Often Should a Furnace Filter be Replaced?

Regularly changing your furnace filter helps to guarantee that the air in your home is cleared of contaminants and dust. How often you should replace the furnace filter depends on a variety of factors. As a leading provider of heating system repair in Cherry Hill and nearby regions, we’ve put together this piece as a small guide to help you understand these factors. All homes use their heating systems for different amounts of time, and all households harbor varying amounts of allergens, pet dander, dust, and dirt.

Open Doors and Windows

Open windows or doors allow dust, allergens, and contaminants to enter your home, adding a layer of dirt to your filters. If you leave your doors and windows open, filters that are one or two inches in size will need replacing every month, four-inch filters every other month, and five-inch filters every three months.


If you live amongst animals, this will contribute to shortening the lifespan of your furnace filter. The more animals that live in your home, the shorter time your filter will last. Housing many animals often require filter changes as follows:

  • Change a one or two-inch filter out every month 
  • Change a four-inch filter every two months 
  • Change a five-inch filter every three months


Smoking in your home will affect your air filter. The more people who smoke inside, the shorter the filter’s lifespan will be. If there is only one smoker in the house, your one or two-inch filters should last two months. There will typically be a four-month turnaround on a four-inch filter and a six-month turnaround on a five-inch filter for light smoking

Heater Fan

If you have a heater fan running fairly frequently, this can affect how often you need to replace the filter. If the fan is on permanently, you’ll need to change the filter every month. If it’s barely used, it will need changing around every two to three months.

A general rule of thumb is to change one and two-inch filter filters once every three months, four-inch filters every six months, and five-inch filters once a year.

For more information, or to book essential heating service repairs in Philadelphia, click here to contact a member of our team.


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