A furnace is a heating unit used to warm up your residential space, which is why it is a vital device during the cold months. It works by blowing heated air through the ducts and delivering it to various rooms throughout your house. It can be powered by electricity, natural gas, or fuel oil, depending on the type of model installed in your home.

One key component of a furnace is the filter, which traps impurities, such as dust, dirt, dander, pollen, debris, and other pollutants, from interfering with proper airflow. Not only does it protect your unit from any potential damages, but it also improves the air quality at home.

However, how often must you change your furnace’s filter? That’s what we’re going to discuss in this article. Keep on reading also to know what signs to look for and what factors to consider when looking to replace your filter.

Signs you need to change your filter

If you’re thinking about when the best time is to change your furnace filter, keep in mind that it depends on your house conditions and certain situations. With that, pay particular attention to the following signs:

  • If it has more specks of dust, dirt, and other debris than usual
  • If it is visibly filthy and unsightly in appearance
  • If there’s no automatic cut, where the furnace continuously runs
  • If you smell foul odors coming from the furnace
  • If there are visible damages to your filter
  • If it’s no longer working at all

When you see one or some of these signs, you must get your filter replaced with a new one immediately so that you won’t compromise the air quality at home.

Factors to consider for changing filter

Keep in mind that a handful of factors will determine the frequency of your filter replacement. These variables contribute to how dirty your filter can get, its function, and its overall condition. Here’s what you need to consider: 

  • Pets: It’s common for accumulated fur and dander to get stuck in the air filter if you have furry family members. If you’re an animal lover, be sure to replace your filter every month.
  • Heating fan: The frequency of heater fan use is directly proportional to the frequency of changing the filter. This means that the more you use your heater fan, the more you must replace the filter. In most cases, do so every two to three months.
  • Home ventilation: If your house isn’t properly ventilated with open doors and windows, it’s easy for outdoor particles and pollutants to build up in your filter. For this reason, consider changing your filter every two months. 
  • House cleanliness: If you and your family don’t keep your home clean and tidy, you can expect to change your filter more frequently. But for the most part, be sure to have filter replacement every three months.


At this point, you now realize that there’s no definite frequency as to when you must change your furnace filter, as it depends on the situation and the factors discussed. Just be sure to be on the lookout for signs of filter replacement outlined above. But one thing’s for sure, changing your filter regularly is a must for your furnace’s maintenance and the benefit of the whole household!

As a family-owned and operated heating and air conditioning company in Morris County, NJ, we provide cooling, heating, air quality, and Hydronics services for both commercial and residential clients. If you need furnace service, whether for installation, repair, or maintenance, request a free estimate from us today!