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How Often Should You Replace Your Furnace Filter?

A clean furnace filter improves air quality and allows your HVAC system to run efficiently. Dust, dirt, and airborne particles can reduce airflow and cause debris to get into components. This can increase wear, cause overheating, and shorten operating life. Replacing your furnace filter, which is a regular maintenance task, is relatively simple, but many homeowners neglect it. That being said, knowing when to replace it depends on a few factors.


The filter of a hard-working furnace will need replacement sooner than one for a heater with less demand. But it’s not that simple. The frequency of replacement can differ from one house to another.

Low-grade fiberglass filters should be replaced about every 30 days. On the other hand, a high-end filter with a pleated design can last 6 months. In general, you should replace your furnace filter every 90 days; any longer and dust, dirt, and allergens may clog it up and decrease system efficiency. Indoor air quality issues can also occur and worsen symptoms for people with allergies or asthma.

The thickness of the filter is another factor to consider. Here’s a look at how thickness relates to recommended replacement times:

  • 1-to-2-inch filters: Change every 1 to 3 months.
  • 3-to-4-inch filters: Replace every 6 to 9 months.
  • 5-to-6-inch filters: Can last 9 to 12 months.


The more you use your furnace, the more quickly the filter will become dirty. Aside from this rule of thumb, here are some considerations that can impact how long your furnace filter lasts:

  • Number of Occupants: People introduce contaminants, such as dust, pollen, hair, dandruff, and others, that affect the life of furnace filters. The more occupants your home has the faster these build up.
  • Opening Windows and Doors: Leaving them open allows outdoor contaminants to circulate in your home, which can strain air and furnace filters; a thinner filter will need to be replaced at least every month.
  • Pets: Dogs, cats, and other furry pets can contribute to shorter filter life. They shed fur and dander that gets released into the air and eventually reaches HVAC filters.
  • Air Quality Products: Poor indoor air quality is unforgiving for filtration components. You can extend your furnace filter’s life by installing air cleaners and air purification systems. Excess dust and smoke, contributed by smokers in your home, have a negative impact on filters.
  • Heater Fan Use: If your heater fan runs more frequently, the filter will need to be changed more often. Constant use means the furnace filter will require monthly replacement.


Scheduling furnace filter replacement is a good idea. But time intervals don’t tell the full story. Replace the filter if you notice the following:

  • The filter looks dirty/its material isn’t visible.
  • Your home isn’t heating as effectively.
  • Less airflow from your HVAC vents.
  • The heating system is running more frequently.
  • Your home becomes dustier than it was.
  • Musty or burning odors emanate from your furnace/vents.


Our licensed, bonded, and insured professionals help home and business owners in the Dallas-Fort Worth area with furnace and HVAC maintenance, installation, and repair. We can help if you’re not sure which filter to install or are looking for a higher-quality one. If your furnace filter is getting dirtier faster, we can perform an inspection to figure out why. Schedule service online or call (817) 631-2507 so our technicians can resolve the issue.

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